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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-26 10:09:38 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-04-26 10:09:38 -0700 |
| commit | 64f8e73de08d11cbe01347340db95b4011872ec5 (patch) | |
| tree | f1a3574482457a91d4eea2af9bc3aeb7b8c26bae /arch/x86/kernel/traps.c | |
| parent | eea2647e74cd7bd5d04861ce55fa502de165de14 (diff) | |
| parent | ebca17707e38f2050b188d837bd4646b29a1b0c2 (diff) | |
| download | linux-stable-64f8e73de08d11cbe01347340db95b4011872ec5.tar.gz linux-stable-64f8e73de08d11cbe01347340db95b4011872ec5.tar.bz2 linux-stable-64f8e73de08d11cbe01347340db95b4011872ec5.zip | |
Merge tag 'x86-splitlock-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 bus lock detection updates from Thomas Gleixner:
"Support for enhanced split lock detection:
Newer CPUs provide a second mechanism to detect operations with lock
prefix which go accross a cache line boundary. Such operations have to
take bus lock which causes a system wide performance degradation when
these operations happen frequently.
The new mechanism is not using the #AC exception. It triggers #DB and
is restricted to operations in user space. Kernel side split lock
access can only be detected by the #AC based variant.
Contrary to the #AC based mechanism the #DB based variant triggers
_after_ the instruction was executed. The mechanism is CPUID
enumerated and contrary to the #AC version which is based on the magic
TEST_CTRL_MSR and model/family based enumeration on the way to become
architectural"
* tag 'x86-splitlock-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Documentation/admin-guide: Change doc for split_lock_detect parameter
x86/traps: Handle #DB for bus lock
x86/cpufeatures: Enumerate #DB for bus lock detection
Diffstat (limited to 'arch/x86/kernel/traps.c')
| -rw-r--r-- | arch/x86/kernel/traps.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 48881db8dca1..f577d07fbd43 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -978,6 +978,10 @@ static __always_inline void exc_debug_user(struct pt_regs *regs, goto out_irq; } + /* #DB for bus lock can only be triggered from userspace. */ + if (dr6 & DR_BUS_LOCK) + handle_bus_lock(regs); + /* Add the virtual_dr6 bits for signals. */ dr6 |= current->thread.virtual_dr6; if (dr6 & (DR_STEP | DR_TRAP_BITS) || icebp) |