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Message-Id: <20200203151608.28053-4-xiaoyao.li@intel.com>
Date: Mon, 3 Feb 2020 23:16:05 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <sean.j.christopherson@...el.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...capital.net>
Cc: x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
David Laight <David.Laight@...lab.com>,
Xiaoyao Li <xiaoyao.li@...el.com>
Subject: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write
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@linux.intel.com
Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
---
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
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