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From: Xiaoyao Li <xiaoyao.li@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Andy Lutomirski <luto@amacapital.net>
Cc: x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	David Laight <David.Laight@aculab.com>,
	Xiaoyao Li <xiaoyao.li@intel.com>
Subject: [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write
Date: Mon,  3 Feb 2020 23:16:05 +0800	[thread overview]
Message-ID: <20200203151608.28053-4-xiaoyao.li@intel.com> (raw)
In-Reply-To: <20200203151608.28053-1-xiaoyao.li@intel.com>

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@intel.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


  parent reply	other threads:[~2020-02-03 15:21 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-03 15:16 [PATCH v2 0/6] kvm/split_lock: Add feature split lock detection support in kvm Xiaoyao Li
2020-02-03 15:16 ` [PATCH v2 1/6] x86/split_lock: Add and export get_split_lock_detect_state() Xiaoyao Li
2020-02-03 21:45   ` Sean Christopherson
2020-02-03 15:16 ` [PATCH v2 2/6] x86/split_lock: Add and export split_lock_detect_set() Xiaoyao Li
2020-02-03 15:16 ` Xiaoyao Li [this message]
2020-02-03 20:54   ` [PATCH v2 3/6] kvm: x86: Emulate split-lock access as a write Sean Christopherson
2020-02-04  2:55     ` Xiaoyao Li
2020-02-11 12:20   ` Paolo Bonzini
2020-02-11 13:22     ` Thomas Gleixner
2020-02-11 13:34       ` Paolo Bonzini
2020-02-11 14:02         ` Xiaoyao Li
2020-02-11 14:34           ` David Laight
2020-02-27  0:11         ` Sean Christopherson
2020-03-12 11:42           ` Xiaoyao Li
2020-03-12 15:00             ` Paolo Bonzini
2020-02-03 15:16 ` [PATCH v2 4/6] kvm: vmx: Extend VMX's #AC handding for split lock in guest Xiaoyao Li
2020-02-03 21:14   ` Sean Christopherson
2020-02-04  6:46     ` Xiaoyao Li
2020-02-10 21:30       ` Sean Christopherson
2020-02-03 15:16 ` [PATCH v2 5/6] kvm: x86: Emulate MSR IA32_CORE_CAPABILITIES Xiaoyao Li
2020-02-03 21:43   ` Sean Christopherson
2020-02-04  9:19     ` Xiaoyao Li
2020-02-04  9:37       ` Peter Zijlstra
2020-02-11  3:52         ` Andy Lutomirski
2020-02-11 12:38           ` Peter Zijlstra
2020-02-03 15:16 ` [PATCH v2 6/6] x86: vmx: virtualize split lock detection Xiaoyao Li
2020-02-03 15:58   ` Xiaoyao Li
2020-02-03 18:52   ` Andy Lutomirski
2020-02-03 21:42   ` Sean Christopherson
2020-02-04  2:52     ` Xiaoyao Li
2020-02-04  5:35       ` Sean Christopherson

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