KVM: LAPIC: Optimize timer latency further

Advance lapic timer tries to hidden the hypervisor overhead between the
host emulated timer fires and the guest awares the timer is fired. However,
it just

KVM: LAPIC: Optimize timer latency further

Advance lapic timer tries to hidden the hypervisor overhead between the
host emulated timer fires and the guest awares the timer is fired. However,
it just hidden the time between apic_timer_fn/handle_preemption_timer ->
wait_lapic_expire, instead of the real position of vmentry which is
mentioned in the orignial commit d0659d946be0 ("KVM: x86: add option to
advance tscdeadline hrtimer expiration"). There is 700+ cpu cycles between
the end of wait_lapic_expire and before world switch on my haswell desktop.

This patch tries to narrow the last gap(wait_lapic_expire -> world switch),
it takes the real overhead time between apic_timer_fn/handle_preemption_timer
and before world switch into consideration when adaptively tuning timer
advancement. The patch can reduce 40% latency (~1600+ cycles to ~1000+ cycles
on a haswell desktop) for kvm-unit-tests/tscdeadline_latency when testing
busy waits.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Liran Alon <liran.alon@oracle.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

show more ...

KVM: LAPIC: Delay trace_kvm_wait_lapic_expire tracepoint to after vmexit

wait_lapic_expire() call was moved above guest_enter_irqoff() because of
its tracepoint, which violated the RCU extended quie

KVM: LAPIC: Delay trace_kvm_wait_lapic_expire tracepoint to after vmexit

wait_lapic_expire() call was moved above guest_enter_irqoff() because of
its tracepoint, which violated the RCU extended quiescent state invoked
by guest_enter_irqoff()[1][2]. This patch simply moves the tracepoint
below guest_exit_irqoff() in vcpu_enter_guest(). Snapshot the delta before
VM-Enter, but trace it after VM-Exit. This can help us to move
wait_lapic_expire() just before vmentry in the later patch.

[1] Commit 8b89fe1f6c43 ("kvm: x86: move tracepoints outside extended quiescent state")
[2] https://patchwork.kernel.org/patch/7821111/

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
[Track whether wait_lapic_expire was called, and do not invoke the tracepoint
if not. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

show more ...

Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux

Merge drm/drm-next into drm-intel-next-queued

Get the HDR dependencies originally merged via drm-misc. Sync up all
i915 changes applied via other trees. And get v5.2-rc2 as the baseline.

Signed-off

Merge drm/drm-next into drm-intel-next-queued

Get the HDR dependencies originally merged via drm-misc. Sync up all
i915 changes applied via other trees. And get v5.2-rc2 as the baseline.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

show more ...

Merge drm/drm-next into drm-misc-next

Backmerging 5.2-rc1 to -misc-next for robher

Signed-off-by: Sean Paul <seanpaul@chromium.org>

Merge branch 'fixes-dra7' into fixes

Merge tag 'v5.2-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into fbdev-for-next

Linux 5.2-rc1

Sync with upstream (which now contains fbdev-v5.2 changes) to
prepare a base

Merge tag 'v5.2-rc1' of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into fbdev-for-next

Linux 5.2-rc1

Sync with upstream (which now contains fbdev-v5.2 changes) to
prepare a base for fbdev-v5.3 changes.

show more ...

Merge tag 'v5.2-rc1' into spi-5.3

Linux 5.2-rc1

Merge branches 'ib-mfd-arm-leds-5.2', 'ib-mfd-gpio-input-leds-power-5.2', 'ib-mfd-pinctrl-5.2-2' and 'ib-mfd-regulator-5.2', tag 'ib-mfd-arm-net-5.2' into ibs-for-mfd-merged

Immutable branch between

Merge branches 'ib-mfd-arm-leds-5.2', 'ib-mfd-gpio-input-leds-power-5.2', 'ib-mfd-pinctrl-5.2-2' and 'ib-mfd-regulator-5.2', tag 'ib-mfd-arm-net-5.2' into ibs-for-mfd-merged

Immutable branch between MFD, ARM and Net due for the 5.2 merge window

show more ...

Merge branch 'linus' into core/urgent, to merge in dependent changes

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Merge tag 'v5.1' into next

Sync up with mainline to bring in the latest APIs.

Merge tag 'asoc-v5.2' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Updates for v5.2

This is a pretty huge set of changes, it's been a pretty active release

Merge tag 'asoc-v5.2' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Updates for v5.2

This is a pretty huge set of changes, it's been a pretty active release
all round but the big thing with this release is the Sound Open Firmware
changes from Intel, providing another DSP framework for use with the
DSPs in their SoCs. This one works with the firmware of the same name
which is free software (unlike the previous DSP firmwares and framework)
and there has been some interest in adoption by other systems already so
hopefully we will see adoption by other vendors in the future.

Other highlights include:

- Support for MCLK/sample rate ratio setting in the generic cards.
- Support for pin switches in the generic cards.
- A big set of improvements to the TLV320AIC32x4 drivers from Annaliese
McDermond.
- New drivers for Freescale audio mixers, several Intel machines,
several Mediatek machines, Meson G12A, Sound Open Firmware and
Spreadtrum compressed audio and DMA devices.

show more ...

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

Pull KVM fixes from Paolo Bonzini:

- PPC and ARM bugfixes from submaintainers

- Fix old Windows versions on AMD (recent regress

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

Pull KVM fixes from Paolo Bonzini:

- PPC and ARM bugfixes from submaintainers

- Fix old Windows versions on AMD (recent regression)

- Fix old Linux versions on processors without EPT

- Fixes for LAPIC timer optimizations

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (21 commits)
KVM: nVMX: Fix size checks in vmx_set_nested_state
KVM: selftests: make hyperv_cpuid test pass on AMD
KVM: lapic: Check for in-kernel LAPIC before deferencing apic pointer
KVM: fix KVM_CLEAR_DIRTY_LOG for memory slots of unaligned size
x86/kvm/mmu: reset MMU context when 32-bit guest switches PAE
KVM: x86: Whitelist port 0x7e for pre-incrementing %rip
Documentation: kvm: fix dirty log ioctl arch lists
KVM: VMX: Move RSB stuffing to before the first RET after VM-Exit
KVM: arm/arm64: Don't emulate virtual timers on userspace ioctls
kvm: arm: Skip stage2 huge mappings for unaligned ipa backed by THP
KVM: arm/arm64: Ensure vcpu target is unset on reset failure
KVM: lapic: Convert guest TSC to host time domain if necessary
KVM: lapic: Allow user to disable adaptive tuning of timer advancement
KVM: lapic: Track lapic timer advance per vCPU
KVM: lapic: Disable timer advancement if adaptive tuning goes haywire
x86: kvm: hyper-v: deal with buggy TLB flush requests from WS2012
KVM: x86: Consider LAPIC TSC-Deadline timer expired if deadline too short
KVM: PPC: Book3S: Protect memslots while validating user address
KVM: PPC: Book3S HV: Perserve PSSCR FAKE_SUSPEND bit on guest exit
KVM: arm/arm64: vgic-v3: Retire pending interrupts on disabling LPIs
...

show more ...

KVM: lapic: Allow user to disable adaptive tuning of timer advancement

The introduction of adaptive tuning of lapic timer advancement did not
allow for the scenario where userspace would want to dis

KVM: lapic: Allow user to disable adaptive tuning of timer advancement

The introduction of adaptive tuning of lapic timer advancement did not
allow for the scenario where userspace would want to disable adaptive
tuning but still employ timer advancement, e.g. for testing purposes or
to handle a use case where adaptive tuning is unable to settle on a
suitable time. This is epecially pertinent now that KVM places a hard
threshold on the maximum advancment time.

Rework the timer semantics to accept signed values, with a value of '-1'
being interpreted as "use adaptive tuning with KVM's internal default",
and any other value being used as an explicit advancement time, e.g. a
time of '0' effectively disables advancement.

Note, this does not completely restore the original behavior of
lapic_timer_advance_ns. Prior to tracking the advancement per vCPU,
which is necessary to support autotuning, userspace could adjust
lapic_timer_advance_ns for *running* vCPU. With per-vCPU tracking, the
module params are snapshotted at vCPU creation, i.e. applying a new
advancement effectively requires restarting a VM.

Dynamically updating a running vCPU is possible, e.g. a helper could be
added to retrieve the desired delay, choosing between the global module
param and the per-VCPU value depending on whether or not auto-tuning is
(globally) enabled, but introduces a great deal of complexity. The
wrapper itself is not complex, but understanding and documenting the
effects of dynamically toggling auto-tuning and/or adjusting the timer
advancement is nigh impossible since the behavior would be dependent on
KVM's implementation as well as compiler optimizations. In other words,
providing stable behavior would require extremely careful consideration
now and in the future.

Given that the expected use of a manually-tuned timer advancement is to
"tune once, run many", use the vastly simpler approach of recognizing
changes to the module params only when creating a new vCPU.

Cc: Liran Alon <liran.alon@oracle.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Cc: stable@vger.kernel.org
Fixes: 3b8a5df6c4dc6 ("KVM: LAPIC: Tune lapic_timer_advance_ns automatically")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

show more ...

KVM: lapic: Track lapic timer advance per vCPU

Automatically adjusting the globally-shared timer advancement could
corrupt the timer, e.g. if multiple vCPUs are concurrently adjusting
the advancemen

KVM: lapic: Track lapic timer advance per vCPU

Automatically adjusting the globally-shared timer advancement could
corrupt the timer, e.g. if multiple vCPUs are concurrently adjusting
the advancement value. That could be partially fixed by using a local
variable for the arithmetic, but it would still be susceptible to a
race when setting timer_advance_adjust_done.

And because virtual_tsc_khz and tsc_scaling_ratio are per-vCPU, the
correct calibration for a given vCPU may not apply to all vCPUs.

Furthermore, lapic_timer_advance_ns is marked __read_mostly, which is
effectively violated when finding a stable advancement takes an extended
amount of timer.

Opportunistically change the definition of lapic_timer_advance_ns to
a u32 so that it matches the style of struct kvm_timer. Explicitly
pass the param to kvm_create_lapic() so that it doesn't have to be
exposed to lapic.c, thus reducing the probability of unintentionally
using the global value instead of the per-vCPU value.

Cc: Liran Alon <liran.alon@oracle.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Cc: stable@vger.kernel.org
Fixes: 3b8a5df6c4dc6 ("KVM: LAPIC: Tune lapic_timer_advance_ns automatically")
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

show more ...

Merge tag 'v4.20' into for-linus

Sync with mainline to get linux/overflow.h among other things.

Merge tag 'v4.20' into next

Merge with mainline to bring in the new APIs.

Merge tag 'v4.20-rc7' of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into fbdev-for-next

Linux 4.20-rc7

Sync with upstream (which now contains fbdev-v4.20 changes) to
prepare a b

Merge tag 'v4.20-rc7' of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux into fbdev-for-next

Linux 4.20-rc7

Sync with upstream (which now contains fbdev-v4.20 changes) to
prepare a base for fbdev-v4.21 changes.

show more ...

Merge drm/drm-next into drm-intel-next-queued

Pull in v4.20-rc3 via drm-next.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Merge remote-tracking branch 'drm/drm-next' into drm-misc-next

drm-next is forwarded to v4.20-rc1, and we need this to make
a patch series apply.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst

Merge remote-tracking branch 'drm/drm-next' into drm-misc-next

drm-next is forwarded to v4.20-rc1, and we need this to make
a patch series apply.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

show more ...

Merge tag 'v4.20-rc2' into next-general

Sync to Linux 4.20-rc2 for downstream developers.

Merge tag 'v4.20-rc1' into omap-for-v4.21/dt-ti-sysc

Linux 4.20-rc1

Merge branch 'fixes-dts' into omap-for-v4.20/fixes

Merge branch 'master' into for-4.20/upstream-fixes

Pull in a merge commit that brought in 3b692c55e58d ("HID: asus: only
support backlight when it's not driven by WMI") so that fixup could be
applie

Merge branch 'master' into for-4.20/upstream-fixes

Pull in a merge commit that brought in 3b692c55e58d ("HID: asus: only
support backlight when it's not driven by WMI") so that fixup could be
applied on top of it.

show more ...

Merge branch 'linus' into perf/urgent, to pick up fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>