Merge tag 'v6.6.68' into for/openbmc/dev-6.6

This is the 6.6.68 stable release

KVM: x86: Play nice with protected guests in complete_hypercall_exit()

commit 9b42d1e8e4fe9dc631162c04caa69b0d1860b0f0 upstream.

Use is_64_bit_hypercall() instead of is_64_bit_mode() to detect a 64

KVM: x86: Play nice with protected guests in complete_hypercall_exit()

commit 9b42d1e8e4fe9dc631162c04caa69b0d1860b0f0 upstream.

Use is_64_bit_hypercall() instead of is_64_bit_mode() to detect a 64-bit
hypercall when completing said hypercall. For guests with protected state,
e.g. SEV-ES and SEV-SNP, KVM must assume the hypercall was made in 64-bit
mode as the vCPU state needed to detect 64-bit mode is unavailable.

Hacking the sev_smoke_test selftest to generate a KVM_HC_MAP_GPA_RANGE
hypercall via VMGEXIT trips the WARN:

------------[ cut here ]------------
WARNING: CPU: 273 PID: 326626 at arch/x86/kvm/x86.h:180 complete_hypercall_exit+0x44/0xe0 [kvm]
Modules linked in: kvm_amd kvm ... [last unloaded: kvm]
CPU: 273 UID: 0 PID: 326626 Comm: sev_smoke_test Not tainted 6.12.0-smp--392e932fa0f3-feat #470
Hardware name: Google Astoria/astoria, BIOS 0.20240617.0-0 06/17/2024
RIP: 0010:complete_hypercall_exit+0x44/0xe0 [kvm]
Call Trace:
<TASK>
kvm_arch_vcpu_ioctl_run+0x2400/0x2720 [kvm]
kvm_vcpu_ioctl+0x54f/0x630 [kvm]
__se_sys_ioctl+0x6b/0xc0
do_syscall_64+0x83/0x160
entry_SYSCALL_64_after_hwframe+0x76/0x7e
</TASK>
---[ end trace 0000000000000000 ]---

Fixes: b5aead0064f3 ("KVM: x86: Assume a 64-bit hypercall for guests with protected state")
Cc: stable@vger.kernel.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Nikunj A Dadhania <nikunj@amd.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20241128004344.4072099-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

KVM: x86: Cache CPUID.0xD XSTATE offsets+sizes during module init

commit 1201f226c863b7da739f7420ddba818cedf372fc upstream.

Snapshot the output of CPUID.0xD.[1..n] during kvm.ko initiliaization to

KVM: x86: Cache CPUID.0xD XSTATE offsets+sizes during module init

commit 1201f226c863b7da739f7420ddba818cedf372fc upstream.

Snapshot the output of CPUID.0xD.[1..n] during kvm.ko initiliaization to
avoid the overead of CPUID during runtime. The offset, size, and metadata
for CPUID.0xD.[1..n] sub-leaves does not depend on XCR0 or XSS values, i.e.
is constant for a given CPU, and thus can be cached during module load.

On Intel's Emerald Rapids, CPUID is *wildly* expensive, to the point where
recomputing XSAVE offsets and sizes results in a 4x increase in latency of
nested VM-Enter and VM-Exit (nested transitions can trigger
xstate_required_size() multiple times per transition), relative to using
cached values. The issue is easily visible by running `perf top` while
triggering nested transitions: kvm_update_cpuid_runtime() shows up at a
whopping 50%.

As measured via RDTSC from L2 (using KVM-Unit-Test's CPUID VM-Exit test
and a slightly modified L1 KVM to handle CPUID in the fastpath), a nested
roundtrip to emulate CPUID on Skylake (SKX), Icelake (ICX), and Emerald
Rapids (EMR) takes:

SKX 11650
ICX 22350
EMR 28850

Using cached values, the latency drops to:

SKX 6850
ICX 9000
EMR 7900

The underlying issue is that CPUID itself is slow on ICX, and comically
slow on EMR. The problem is exacerbated on CPUs which support XSAVES
and/or XSAVEC, as KVM invokes xstate_required_size() twice on each
runtime CPUID update, and because there are more supported XSAVE features
(CPUID for supported XSAVE feature sub-leafs is significantly slower).

SKX:
CPUID.0xD.2 = 348 cycles
CPUID.0xD.3 = 400 cycles
CPUID.0xD.4 = 276 cycles
CPUID.0xD.5 = 236 cycles
<other sub-leaves are similar>

EMR:
CPUID.0xD.2 = 1138 cycles
CPUID.0xD.3 = 1362 cycles
CPUID.0xD.4 = 1068 cycles
CPUID.0xD.5 = 910 cycles
CPUID.0xD.6 = 914 cycles
CPUID.0xD.7 = 1350 cycles
CPUID.0xD.8 = 734 cycles
CPUID.0xD.9 = 766 cycles
CPUID.0xD.10 = 732 cycles
CPUID.0xD.11 = 718 cycles
CPUID.0xD.12 = 734 cycles
CPUID.0xD.13 = 1700 cycles
CPUID.0xD.14 = 1126 cycles
CPUID.0xD.15 = 898 cycles
CPUID.0xD.16 = 716 cycles
CPUID.0xD.17 = 748 cycles
CPUID.0xD.18 = 776 cycles

Note, updating runtime CPUID information multiple times per nested
transition is itself a flaw, especially since CPUID is a mandotory
intercept on both Intel and AMD. E.g. KVM doesn't need to ensure emulated
CPUID state is up-to-date while running L2. That flaw will be fixed in a
future patch, as deferring runtime CPUID updates is more subtle than it
appears at first glance, the benefits aren't super critical to have once
the XSAVE issue is resolved, and caching CPUID output is desirable even if
KVM's updates are deferred.

Cc: Jim Mattson <jmattson@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20241211013302.1347853-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.51' into for/openbmc/dev-6.6

This is the 6.6.51 stable release

KVM: x86: Acquire kvm->srcu when handling KVM_SET_VCPU_EVENTS

commit 4bcdd831d9d01e0fb64faea50732b59b2ee88da1 upstream.

Grab kvm->srcu when processing KVM_SET_VCPU_EVENTS, as KVM will forcibly
leav

KVM: x86: Acquire kvm->srcu when handling KVM_SET_VCPU_EVENTS

commit 4bcdd831d9d01e0fb64faea50732b59b2ee88da1 upstream.

Grab kvm->srcu when processing KVM_SET_VCPU_EVENTS, as KVM will forcibly
leave nested VMX/SVM if SMM mode is being toggled, and leaving nested VMX
reads guest memory.

Note, kvm_vcpu_ioctl_x86_set_vcpu_events() can also be called from KVM_RUN
via sync_regs(), which already holds SRCU. I.e. trying to precisely use
kvm_vcpu_srcu_read_lock() around the problematic SMM code would cause
problems. Acquiring SRCU isn't all that expensive, so for simplicity,
grab it unconditionally for KVM_SET_VCPU_EVENTS.

=============================
WARNING: suspicious RCU usage
6.10.0-rc7-332d2c1d713e-next-vm #552 Not tainted
-----------------------------
include/linux/kvm_host.h:1027 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by repro/1071:
#0: ffff88811e424430 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x7d/0x970 [kvm]

stack backtrace:
CPU: 15 PID: 1071 Comm: repro Not tainted 6.10.0-rc7-332d2c1d713e-next-vm #552
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Call Trace:
<TASK>
dump_stack_lvl+0x7f/0x90
lockdep_rcu_suspicious+0x13f/0x1a0
kvm_vcpu_gfn_to_memslot+0x168/0x190 [kvm]
kvm_vcpu_read_guest+0x3e/0x90 [kvm]
nested_vmx_load_msr+0x6b/0x1d0 [kvm_intel]
load_vmcs12_host_state+0x432/0xb40 [kvm_intel]
vmx_leave_nested+0x30/0x40 [kvm_intel]
kvm_vcpu_ioctl_x86_set_vcpu_events+0x15d/0x2b0 [kvm]
kvm_arch_vcpu_ioctl+0x1107/0x1750 [kvm]
? mark_held_locks+0x49/0x70
? kvm_vcpu_ioctl+0x7d/0x970 [kvm]
? kvm_vcpu_ioctl+0x497/0x970 [kvm]
kvm_vcpu_ioctl+0x497/0x970 [kvm]
? lock_acquire+0xba/0x2d0
? find_held_lock+0x2b/0x80
? do_user_addr_fault+0x40c/0x6f0
? lock_release+0xb7/0x270
__x64_sys_ioctl+0x82/0xb0
do_syscall_64+0x6c/0x170
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7ff11eb1b539
</TASK>

Fixes: f7e570780efc ("KVM: x86: Forcibly leave nested virt when SMM state is toggled")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240723232055.3643811-1-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.44' into for/openbmc/dev-6.6

This is the 6.6.44 stable release

KVM: nVMX: Request immediate exit iff pending nested event needs injection

commit 32f55e475ce2c4b8b124d335fcfaf1152ba977a1 upstream.

When requesting an immediate exit from L2 in order to inject a p

KVM: nVMX: Request immediate exit iff pending nested event needs injection

commit 32f55e475ce2c4b8b124d335fcfaf1152ba977a1 upstream.

When requesting an immediate exit from L2 in order to inject a pending
event, do so only if the pending event actually requires manual injection,
i.e. if and only if KVM actually needs to regain control in order to
deliver the event.

Avoiding the "immediate exit" isn't simply an optimization, it's necessary
to make forward progress, as the "already expired" VMX preemption timer
trick that KVM uses to force a VM-Exit has higher priority than events
that aren't directly injected.

At present time, this is a glorified nop as all events processed by
vmx_has_nested_events() require injection, but that will not hold true in
the future, e.g. if there's a pending virtual interrupt in vmcs02.RVI.
I.e. if KVM is trying to deliver a virtual interrupt to L2, the expired
VMX preemption timer will trigger VM-Exit before the virtual interrupt is
delivered, and KVM will effectively hang the vCPU in an endless loop of
forced immediate VM-Exits (because the pending virtual interrupt never
goes away).

Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240607172609.3205077-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.36' into dev-6.6

This is the 6.6.36 stable release

KVM: x86: Always sync PIR to IRR prior to scanning I/O APIC routes

commit f3ced000a2df53f4b12849e121769045a81a3b22 upstream.

Sync pending posted interrupts to the IRR prior to re-scanning I/O APIC

KVM: x86: Always sync PIR to IRR prior to scanning I/O APIC routes

commit f3ced000a2df53f4b12849e121769045a81a3b22 upstream.

Sync pending posted interrupts to the IRR prior to re-scanning I/O APIC
routes, irrespective of whether the I/O APIC is emulated by userspace or
by KVM. If a level-triggered interrupt routed through the I/O APIC is
pending or in-service for a vCPU, KVM needs to intercept EOIs on said
vCPU even if the vCPU isn't the destination for the new routing, e.g. if
servicing an interrupt using the old routing races with I/O APIC
reconfiguration.

Commit fceb3a36c29a ("KVM: x86: ioapic: Fix level-triggered EOI and
userspace I/OAPIC reconfigure race") fixed the common cases, but
kvm_apic_pending_eoi() only checks if an interrupt is in the local
APIC's IRR or ISR, i.e. misses the uncommon case where an interrupt is
pending in the PIR.

Failure to intercept EOI can manifest as guest hangs with Windows 11 if
the guest uses the RTC as its timekeeping source, e.g. if the VMM doesn't
expose a more modern form of time to the guest.

Cc: stable@vger.kernel.org
Cc: Adamos Ttofari <attofari@amazon.de>
Cc: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240611014845.82795-1-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.29' into dev-6.6

This is the 6.6.29 stable release

KVM: x86: Snapshot if a vCPU's vendor model is AMD vs. Intel compatible

commit fd706c9b1674e2858766bfbf7430534c2b26fbef upstream.

Add kvm_vcpu_arch.is_amd_compatible to cache if a vCPU's vendor mod

KVM: x86: Snapshot if a vCPU's vendor model is AMD vs. Intel compatible

commit fd706c9b1674e2858766bfbf7430534c2b26fbef upstream.

Add kvm_vcpu_arch.is_amd_compatible to cache if a vCPU's vendor model is
compatible with AMD, i.e. if the vCPU vendor is AMD or Hygon, along with
helpers to check if a vCPU is compatible AMD vs. Intel. To handle Intel
vs. AMD behavior related to masking the LVTPC entry, KVM will need to
check for vendor compatibility on every PMI injection, i.e. querying for
AMD will soon be a moderately hot path.

Note! This subtly (or maybe not-so-subtly) makes "Intel compatible" KVM's
default behavior, both if userspace omits (or never sets) CPUID 0x0 and if
userspace sets a completely unknown vendor. One could argue that KVM
should treat such vCPUs as not being compatible with Intel *or* AMD, but
that would add useless complexity to KVM.

KVM needs to do *something* in the face of vendor specific behavior, and
so unless KVM conjured up a magic third option, choosing to treat unknown
vendors as neither Intel nor AMD means that checks on AMD compatibility
would yield Intel behavior, and checks for Intel compatibility would yield
AMD behavior. And that's far worse as it would effectively yield random
behavior depending on whether KVM checked for AMD vs. Intel vs. !AMD vs.
!Intel. And practically speaking, all x86 CPUs follow either Intel or AMD
architecture, i.e. "supporting" an unknown third architecture adds no
value.

Deliberately don't convert any of the existing guest_cpuid_is_intel()
checks, as the Intel side of things is messier due to some flows explicitly
checking for exactly vendor==Intel, versus some flows assuming anything
that isn't "AMD compatible" gets Intel behavior. The Intel code will be
cleaned up in the future.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240405235603.1173076-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.26' into dev-6.6

This is the 6.6.26 stable release

KVM: x86: Add BHI_NO

commit ed2e8d49b54d677f3123668a21a57822d679651f upstream.

Intel processors that aren't vulnerable to BHI will set
MSR_IA32_ARCH_CAPABILITIES[BHI_NO] = 1;. Guests may use this B

KVM: x86: Add BHI_NO

commit ed2e8d49b54d677f3123668a21a57822d679651f upstream.

Intel processors that aren't vulnerable to BHI will set
MSR_IA32_ARCH_CAPABILITIES[BHI_NO] = 1;. Guests may use this BHI_NO bit to
determine if they need to implement BHI mitigations or not. Allow this bit
to be passed to the guests.

Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.24' into dev-6.6

This is the 6.6.24 stable release

KVM: x86: Mark target gfn of emulated atomic instruction as dirty

commit 910c57dfa4d113aae6571c2a8b9ae8c430975902 upstream.

When emulating an atomic access on behalf of the guest, mark the target
g

KVM: x86: Mark target gfn of emulated atomic instruction as dirty

commit 910c57dfa4d113aae6571c2a8b9ae8c430975902 upstream.

When emulating an atomic access on behalf of the guest, mark the target
gfn dirty if the CMPXCHG by KVM is attempted and doesn't fault. This
fixes a bug where KVM effectively corrupts guest memory during live
migration by writing to guest memory without informing userspace that the
page is dirty.

Marking the page dirty got unintentionally dropped when KVM's emulated
CMPXCHG was converted to do a user access. Before that, KVM explicitly
mapped the guest page into kernel memory, and marked the page dirty during
the unmap phase.

Mark the page dirty even if the CMPXCHG fails, as the old data is written
back on failure, i.e. the page is still written. The value written is
guaranteed to be the same because the operation is atomic, but KVM's ABI
is that all writes are dirty logged regardless of the value written. And
more importantly, that's what KVM did before the buggy commit.

Huge kudos to the folks on the Cc list (and many others), who did all the
actual work of triaging and debugging.

Fixes: 1c2361f667f3 ("KVM: x86: Use __try_cmpxchg_user() to emulate atomic accesses")
Cc: stable@vger.kernel.org
Cc: David Matlack <dmatlack@google.com>
Cc: Pasha Tatashin <tatashin@google.com>
Cc: Michael Krebs <mkrebs@google.com>
base-commit: 6769ea8da8a93ed4630f1ce64df6aafcaabfce64
Reviewed-by: Jim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20240215010004.1456078-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.22' into dev-6.6

Linux 6.6.22

KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests

commit 2a0180129d726a4b953232175857d442651b55a0 upstream.

Mitigation for RFDS requires RFDS_CLEAR capability which is enumerated
by MSR_IA32_ARCH_CA

KVM/x86: Export RFDS_NO and RFDS_CLEAR to guests

commit 2a0180129d726a4b953232175857d442651b55a0 upstream.

Mitigation for RFDS requires RFDS_CLEAR capability which is enumerated
by MSR_IA32_ARCH_CAPABILITIES bit 27. If the host has it set, export it
to guests so that they can deploy the mitigation.

RFDS_NO indicates that the system is not vulnerable to RFDS, export it
to guests so that they don't deploy the mitigation unnecessarily. When
the host is not affected by X86_BUG_RFDS, but has RFDS_NO=0, synthesize
RFDS_NO to the guest.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.18' into dev-6.6

This is the 6.6.18 stable release

KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu

commit 6231c9e1a9f35b535c66709aa8a6eda40dbc4132 upstream.

kvm_vcpu_ioctl_x86_set_vcpu_events() routine makes 'KVM_REQ_NMI'
request for a

KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu

commit 6231c9e1a9f35b535c66709aa8a6eda40dbc4132 upstream.

kvm_vcpu_ioctl_x86_set_vcpu_events() routine makes 'KVM_REQ_NMI'
request for a vcpu even when its 'events->nmi.pending' is zero.
Ex:
qemu_thread_start
kvm_vcpu_thread_fn
qemu_wait_io_event
qemu_wait_io_event_common
process_queued_cpu_work
do_kvm_cpu_synchronize_post_init/_reset
kvm_arch_put_registers
kvm_put_vcpu_events (cpu, level=[2|3])

This leads vCPU threads in QEMU to constantly acquire & release the
global mutex lock, delaying the guest boot due to lock contention.
Add check to make KVM_REQ_NMI request only if vcpu has NMI pending.

Fixes: bdedff263132 ("KVM: x86: Route pending NMIs from userspace through process_nmi()")
Cc: stable@vger.kernel.org
Signed-off-by: Prasad Pandit <pjp@fedoraproject.org>
Link: https://lore.kernel.org/r/20240103075343.549293-1-ppandit@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'v6.6.6' into dev-6.6

This is the 6.6.6 stable release

Signed-off-by: Joel Stanley <joel@jms.id.au>

KVM: x86: Ignore MSR_AMD64_TW_CFG access

commit 2770d4722036d6bd24bcb78e9cd7f6e572077d03 upstream.

Hyper-V enabled Windows Server 2022 KVM VM cannot be started on Zen1 Ryzen
since it crashes at boo

KVM: x86: Ignore MSR_AMD64_TW_CFG access

commit 2770d4722036d6bd24bcb78e9cd7f6e572077d03 upstream.

Hyper-V enabled Windows Server 2022 KVM VM cannot be started on Zen1 Ryzen
since it crashes at boot with SYSTEM_THREAD_EXCEPTION_NOT_HANDLED +
STATUS_PRIVILEGED_INSTRUCTION (in other words, because of an unexpected #GP
in the guest kernel).

This is because Windows tries to set bit 8 in MSR_AMD64_TW_CFG and can't
handle receiving a #GP when doing so.

Give this MSR the same treatment that commit 2e32b7190641
("x86, kvm: Add MSR_AMD64_BU_CFG2 to the list of ignored MSRs") gave
MSR_AMD64_BU_CFG2 under justification that this MSR is baremetal-relevant
only.
Although apparently it was then needed for Linux guests, not Windows as in
this case.

With this change, the aforementioned guest setup is able to finish booting
successfully.

This issue can be reproduced either on a Summit Ridge Ryzen (with
just "-cpu host") or on a Naples EPYC (with "-cpu host,stepping=1" since
EPYC is ordinarily stepping 2).

Alternatively, userspace could solve the problem by using MSR filters, but
forcing every userspace to define a filter isn't very friendly and doesn't
add much, if any, value. The only potential hiccup is if one of these
"baremetal-only" MSRs ever requires actual emulation and/or has F/M/S
specific behavior. But if that happens, then KVM can still punt *that*
handling to userspace since userspace MSR filters "win" over KVM's default
handling.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/1ce85d9c7c9e9632393816cf19c902e0a3f411f1.1697731406.git.maciej.szmigiero@oracle.com
[sean: call out MSR filtering alternative]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:
"ARM:

- Fix the handling of the phycal timer offset when FEAT_ECV and
CNTPOFF_EL2 are

Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull kvm fixes from Paolo Bonzini:
"ARM:

- Fix the handling of the phycal timer offset when FEAT_ECV and
CNTPOFF_EL2 are implemented

- Restore the functionnality of Permission Indirection that was
broken by the Fine Grained Trapping rework

- Cleanup some PMU event sharing code

MIPS:

- Fix W=1 build

s390:

- One small fix for gisa to avoid stalls

x86:

- Truncate writes to PMU counters to the counter's width to avoid
spurious overflows when emulating counter events in software

- Set the LVTPC entry mask bit when handling a PMI (to match
Intel-defined architectural behavior)

- Treat KVM_REQ_PMI as a wake event instead of queueing host IRQ work
to kick the guest out of emulated halt

- Fix for loading XSAVE state from an old kernel into a new one

- Fixes for AMD AVIC

selftests:

- Play nice with %llx when formatting guest printf and assert
statements

- Clean up stale test metadata

- Zero-initialize structures in memslot perf test to workaround a
suspected 'may be used uninitialized' false positives from GCC"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (21 commits)
KVM: arm64: timers: Correctly handle TGE flip with CNTPOFF_EL2
KVM: arm64: POR{E0}_EL1 do not need trap handlers
KVM: arm64: Add nPIR{E0}_EL1 to HFG traps
KVM: MIPS: fix -Wunused-but-set-variable warning
KVM: arm64: pmu: Drop redundant check for non-NULL kvm_pmu_events
KVM: SVM: Fix build error when using -Werror=unused-but-set-variable
x86: KVM: SVM: refresh AVIC inhibition in svm_leave_nested()
x86: KVM: SVM: add support for Invalid IPI Vector interception
x86: KVM: SVM: always update the x2avic msr interception
KVM: selftests: Force load all supported XSAVE state in state test
KVM: selftests: Load XSAVE state into untouched vCPU during state test
KVM: selftests: Touch relevant XSAVE state in guest for state test
KVM: x86: Constrain guest-supported xfeatures only at KVM_GET_XSAVE{2}
x86/fpu: Allow caller to constrain xfeatures when copying to uabi buffer
KVM: selftests: Zero-initialize entire test_result in memslot perf test
KVM: selftests: Remove obsolete and incorrect test case metadata
KVM: selftests: Treat %llx like %lx when formatting guest printf
KVM: x86/pmu: Synthesize at most one PMI per VM-exit
KVM: x86: Mask LVTPC when handling a PMI
KVM: x86/pmu: Truncate counter value to allowed width on write
...

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Merge tag 'kvm-x86-pmu-6.6-fixes' of https://github.com/kvm-x86/linux into HEAD

KVM x86/pmu fixes for 6.6:

- Truncate writes to PMU counters to the counter's width to avoid spurious
overflows w

Merge tag 'kvm-x86-pmu-6.6-fixes' of https://github.com/kvm-x86/linux into HEAD

KVM x86/pmu fixes for 6.6:

- Truncate writes to PMU counters to the counter's width to avoid spurious
overflows when emulating counter events in software.

- Set the LVTPC entry mask bit when handling a PMI (to match Intel-defined
architectural behavior).

- Treat KVM_REQ_PMI as a wake event instead of queueing host IRQ work to
kick the guest out of emulated halt.

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KVM: x86: Constrain guest-supported xfeatures only at KVM_GET_XSAVE{2}

Mask off xfeatures that aren't exposed to the guest only when saving guest
state via KVM_GET_XSAVE{2} instead of modifying user

KVM: x86: Constrain guest-supported xfeatures only at KVM_GET_XSAVE{2}

Mask off xfeatures that aren't exposed to the guest only when saving guest
state via KVM_GET_XSAVE{2} instead of modifying user_xfeatures directly.
Preserving the maximal set of xfeatures in user_xfeatures restores KVM's
ABI for KVM_SET_XSAVE, which prior to commit ad856280ddea ("x86/kvm/fpu:
Limit guest user_xfeatures to supported bits of XCR0") allowed userspace
to load xfeatures that are supported by the host, irrespective of what
xfeatures are exposed to the guest.

There is no known use case where userspace *intentionally* loads xfeatures
that aren't exposed to the guest, but the bug fixed by commit ad856280ddea
was specifically that KVM_GET_SAVE{2} would save xfeatures that weren't
exposed to the guest, e.g. would lead to userspace unintentionally loading
guest-unsupported xfeatures when live migrating a VM.

Restricting KVM_SET_XSAVE to guest-supported xfeatures is especially
problematic for QEMU-based setups, as QEMU has a bug where instead of
terminating the VM if KVM_SET_XSAVE fails, QEMU instead simply stops
loading guest state, i.e. resumes the guest after live migration with
incomplete guest state, and ultimately results in guest data corruption.

Note, letting userspace restore all host-supported xfeatures does not fix
setups where a VM is migrated from a host *without* commit ad856280ddea,
to a target with a subset of host-supported xfeatures. However there is
no way to safely address that scenario, e.g. KVM could silently drop the
unsupported features, but that would be a clear violation of KVM's ABI and
so would require userspace to opt-in, at which point userspace could
simply be updated to sanitize the to-be-loaded XSAVE state.

Reported-by: Tyler Stachecki <stachecki.tyler@gmail.com>
Closes: https://lore.kernel.org/all/20230914010003.358162-1-tstachecki@bloomberg.net
Fixes: ad856280ddea ("x86/kvm/fpu: Limit guest user_xfeatures to supported bits of XCR0")
Cc: stable@vger.kernel.org
Cc: Leonardo Bras <leobras@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Message-Id: <20230928001956.924301-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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x86/fpu: Allow caller to constrain xfeatures when copying to uabi buffer

Plumb an xfeatures mask into __copy_xstate_to_uabi_buf() so that KVM can
constrain which xfeatures are saved into the userspa

x86/fpu: Allow caller to constrain xfeatures when copying to uabi buffer

Plumb an xfeatures mask into __copy_xstate_to_uabi_buf() so that KVM can
constrain which xfeatures are saved into the userspace buffer without
having to modify the user_xfeatures field in KVM's guest_fpu state.

KVM's ABI for KVM_GET_XSAVE{2} is that features that are not exposed to
guest must not show up in the effective xstate_bv field of the buffer.
Saving only the guest-supported xfeatures allows userspace to load the
saved state on a different host with a fewer xfeatures, so long as the
target host supports the xfeatures that are exposed to the guest.

KVM currently sets user_xfeatures directly to restrict KVM_GET_XSAVE{2} to
the set of guest-supported xfeatures, but doing so broke KVM's historical
ABI for KVM_SET_XSAVE, which allows userspace to load any xfeatures that
are supported by the *host*.

Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230928001956.924301-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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