diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2020-05-29 23:27:36 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-06-11 15:15:22 +0200 |
| commit | 84b6a3491567a540f955e18d8e615493afa36df0 (patch) | |
| tree | 6cb78ccb03028398a87ffff420648ed4637c1488 /arch/x86/include | |
| parent | cd840e424f27fcc1ae8d14b7ec3ec4560ee6561a (diff) | |
x86/entry: Optimize local_db_save() for virt
Because DRn access is 'difficult' with virt; but the DR7 read is cheaper
than a cacheline miss on native, add a virt specific fast path to
local_db_save(), such that when breakpoints are not in use to avoid
touching DRn entirely.
Suggested-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200529213321.187833200@infradead.org
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/debugreg.h | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h index 4ef8690be8a7..3e1c5021d0f8 100644 --- a/arch/x86/include/asm/debugreg.h +++ b/arch/x86/include/asm/debugreg.h @@ -85,7 +85,7 @@ static inline void hw_breakpoint_disable(void) set_debugreg(0UL, 3); } -static inline int hw_breakpoint_active(void) +static inline bool hw_breakpoint_active(void) { return __this_cpu_read(cpu_dr7) & DR_GLOBAL_ENABLE_MASK; } @@ -117,6 +117,9 @@ static __always_inline unsigned long local_db_save(void) { unsigned long dr7; + if (static_cpu_has(X86_FEATURE_HYPERVISOR) && !hw_breakpoint_active()) + return 0; + get_debugreg(dr7, 7); dr7 &= ~0x400; /* architecturally set bit */ if (dr7) |