x86/32: Remove CONFIG_DOUBLEFAULT

Make the doublefault exception handler unconditional on 32-bit. Yes,
it is important to be able to catch #DF exceptions instead of silent
reboots. Yes, the code siz

x86/32: Remove CONFIG_DOUBLEFAULT

Make the doublefault exception handler unconditional on 32-bit. Yes,
it is important to be able to catch #DF exceptions instead of silent
reboots. Yes, the code size increase is worth every byte. And one less
CONFIG symbol is just the cherry on top.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200404083646.8897-1-bp@alien8.de

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Merge drm-intel-next-queued into gvt-next

Backmerge to pull in
https://patchwork.freedesktop.org/patch/353621/?series=73544&rev=1

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

Merge tag 'v5.5-rc4' into locking/kcsan, to resolve conflicts

Conflicts:
init/main.c
lib/Kconfig.debug

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

Merge branch 'next' into for-linus

Prepare input updates for 5.6 merge window.

Merge tag 'v5.5-rc5' into next

Sync up with mainline to get SPI "delay" API changes.

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

Requested, and we need v5.5-rc1 backported as our current branch is still based on v5.4.

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

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

Sync up with v5.5-rc1 to get the updated lock_release() API among other
things. Fix the conflict reported by Stephen Rothwell [1].

[1] http://lore.kern

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

Sync up with v5.5-rc1 to get the updated lock_release() API among other
things. Fix the conflict reported by Stephen Rothwell [1].

[1] http://lore.kernel.org/r/20191210093957.5120f717@canb.auug.org.au

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

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Merge tag 'v5.5-rc1' into core/kprobes, to resolve conflicts

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

Merge branch 'linus' into sched/urgent, to pick up the latest before merging new patches

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

Merge mainline/master into arm/fixes

This brings in the mainline tree right after armsoc contents was merged
this release cycle, so that we can re-run savedefconfig, etc.

Signed-off-by: Olof Johans

Merge mainline/master into arm/fixes

This brings in the mainline tree right after armsoc contents was merged
this release cycle, so that we can re-run savedefconfig, etc.

Signed-off-by: Olof Johansson <olof@lixom.net>

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Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:
"Various fixes:

- Fix the PAT performance regression that downgrade

Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Ingo Molnar:
"Various fixes:

- Fix the PAT performance regression that downgraded write-combining
device memory regions to uncached.

- There's been a number of bugs in 32-bit double fault handling -
hopefully all fixed now.

- Fix an LDT crash

- Fix an FPU over-optimization that broke with GCC9 code
optimizations.

- Misc cleanups"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/mm/pat: Fix off-by-one bugs in interval tree search
x86/ioperm: Save an indentation level in tss_update_io_bitmap()
x86/fpu: Don't cache access to fpu_fpregs_owner_ctx
x86/entry/32: Remove unused 'restore_all_notrace' local label
x86/ptrace: Document FSBASE and GSBASE ABI oddities
x86/ptrace: Remove set_segment_reg() implementations for current
x86/traps: die() instead of panicking on a double fault
x86/doublefault/32: Rewrite the x86_32 #DF handler and unify with 64-bit
x86/doublefault/32: Move #DF stack and TSS to cpu_entry_area
x86/doublefault/32: Rename doublefault.c to doublefault_32.c
x86/traps: Disentangle the 32-bit and 64-bit doublefault code
lkdtm: Add a DOUBLE_FAULT crash type on x86
selftests/x86/single_step_syscall: Check SYSENTER directly
x86/mm/32: Sync only to VMALLOC_END in vmalloc_sync_all()

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x86/doublefault/32: Move #DF stack and TSS to cpu_entry_area

There are three problems with the current layout of the doublefault
stack and TSS. First, the TSS is only cacheline-aligned, which is
no

x86/doublefault/32: Move #DF stack and TSS to cpu_entry_area

There are three problems with the current layout of the doublefault
stack and TSS. First, the TSS is only cacheline-aligned, which is
not enough -- if the hardware portion of the TSS (struct x86_hw_tss)
crosses a page boundary, horrible things happen [0]. Second, the
stack and TSS are global, so simultaneous double faults on different
CPUs will cause massive corruption. Third, the whole mechanism
won't work if user CR3 is loaded, resulting in a triple fault [1].

Let the doublefault stack and TSS share a page (which prevents the
TSS from spanning a page boundary), make it percpu, and move it into
cpu_entry_area. Teach the stack dump code about the doublefault
stack.

[0] Real hardware will read past the end of the page onto the next
*physical* page if a task switch happens. Virtual machines may
have any number of bugs, and I would consider it reasonable for
a VM to summarily kill the guest if it tries to task-switch to
a page-spanning TSS.

[1] Real hardware triple faults. At least some VMs seem to hang.
I'm not sure what's going on.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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