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| author | Andy Lutomirski <luto@kernel.org> | 2016-04-02 16:01:37 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-04-13 11:37:45 +0200 |
| commit | fbd704374d111bed16a19261176fa30e2379c87c (patch) | |
| tree | 8b1de7476a88eae86f76dc929c37e5a129c94e6c /arch/x86/include | |
| parent | x86/paravirt: Add _safe to the read_ms()r and write_msr() PV callbacks (diff) | |
| download | linux-fbd704374d111bed16a19261176fa30e2379c87c.tar.xz linux-fbd704374d111bed16a19261176fa30e2379c87c.zip | |
x86/msr: Carry on after a non-"safe" MSR access fails
This demotes an OOPS and likely panic due to a failed non-"safe" MSR
access to a WARN_ONCE() and, for RDMSR, a return value of zero.
To be clear, this type of failure should *not* happen. This patch
exists to minimize the chance of nasty undebuggable failures
happening when a CONFIG_PARAVIRT=y bug in the non-"safe" MSR helpers
gets fixed.
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/26567b216aae70e795938f4b567eace5a0eb90ba.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/msr.h | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h index 7a79ee2778b3..25f169c6eb95 100644 --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -84,7 +84,10 @@ static inline unsigned long long native_read_msr(unsigned int msr) { DECLARE_ARGS(val, low, high); - asm volatile("rdmsr" : EAX_EDX_RET(val, low, high) : "c" (msr)); + asm volatile("1: rdmsr\n" + "2:\n" + _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_rdmsr_unsafe) + : EAX_EDX_RET(val, low, high) : "c" (msr)); if (msr_tracepoint_active(__tracepoint_read_msr)) do_trace_read_msr(msr, EAX_EDX_VAL(val, low, high), 0); return EAX_EDX_VAL(val, low, high); @@ -111,7 +114,10 @@ static inline unsigned long long native_read_msr_safe(unsigned int msr, static inline void native_write_msr(unsigned int msr, unsigned low, unsigned high) { - asm volatile("wrmsr" : : "c" (msr), "a"(low), "d" (high) : "memory"); + asm volatile("1: wrmsr\n" + "2:\n" + _ASM_EXTABLE_HANDLE(1b, 2b, ex_handler_wrmsr_unsafe) + : : "c" (msr), "a"(low), "d" (high) : "memory"); if (msr_tracepoint_active(__tracepoint_read_msr)) do_trace_write_msr(msr, ((u64)high << 32 | low), 0); } |