If split lock detect is enabled (warn/fatal), #AC handler calls die() when split lock happens in kernel. A sane guest should never tigger emulation on a split-lock access, but it cannot prevent malicous guest from doing this. So just emulating the access as a write if it's a split-lock access to avoid malicous guest polluting the kernel log. More detail analysis can be found: https://lkml.kernel.org/r/20200131200134.GD18946@xxxxxxxxxxxxxxx Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx> --- arch/x86/kvm/x86.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 2d3be7f3ad67..821b7404c0fd 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5847,6 +5847,13 @@ static int emulator_write_emulated(struct x86_emulate_ctxt *ctxt, (cmpxchg64((u64 *)(ptr), *(u64 *)(old), *(u64 *)(new)) == *(u64 *)(old)) #endif +static inline bool across_cache_line_access(gpa_t gpa, unsigned int bytes) +{ + unsigned int cache_line_size = cache_line_size(); + + return (gpa & (cache_line_size - 1)) + bytes > cache_line_size; +} + static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, unsigned long addr, const void *old, @@ -5873,6 +5880,10 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt, if (((gpa + bytes - 1) & PAGE_MASK) != (gpa & PAGE_MASK)) goto emul_write; + if (get_split_lock_detect_state() != sld_off && + across_cache_line_access(gpa, bytes)) + goto emul_write; + if (kvm_vcpu_map(vcpu, gpa_to_gfn(gpa), &map)) goto emul_write; -- 2.23.0
