Blame KVM-x86-handle-idiv-overflow-at-kvm_write_tsc.patch
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
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index 094b5d9..64a4b03 100644
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--- a/arch/x86/kvm/x86.c
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+++ b/arch/x86/kvm/x86.c
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@@ -1194,20 +1194,37 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr)
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elapsed = ns - kvm->arch.last_tsc_nsec;
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if (vcpu->arch.virtual_tsc_khz) {
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+ int faulted = 0;
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+
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/* n.b - signed multiplication and division required */
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usdiff = data - kvm->arch.last_tsc_write;
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#ifdef CONFIG_X86_64
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usdiff = (usdiff * 1000) / vcpu->arch.virtual_tsc_khz;
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#else
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/* do_div() only does unsigned */
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- asm("idivl %2; xor %%edx, %%edx"
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- : "=A"(usdiff)
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- : "A"(usdiff * 1000), "rm"(vcpu->arch.virtual_tsc_khz));
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+ asm("1: idivl %[divisor]\n"
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+ "2: xor %%edx, %%edx\n"
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+ " movl $0, %[faulted]\n"
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+ "3:\n"
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+ ".section .fixup,\"ax\"\n"
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+ "4: movl $1, %[faulted]\n"
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+ " jmp 3b\n"
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+ ".previous\n"
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+
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+ _ASM_EXTABLE(1b, 4b)
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+
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+ : "=A"(usdiff), [faulted] "=r" (faulted)
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+ : "A"(usdiff * 1000), [divisor] "rm"(vcpu->arch.virtual_tsc_khz));
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+
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#endif
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do_div(elapsed, 1000);
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usdiff -= elapsed;
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if (usdiff < 0)
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usdiff = -usdiff;
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+
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+ /* idivl overflow => difference is larger than USEC_PER_SEC */
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+ if (faulted)
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+ usdiff = USEC_PER_SEC;
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} else
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usdiff = USEC_PER_SEC; /* disable TSC match window below */
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