KVM: MTRR: observe maxphyaddr from guest CPUID, not host (fa7c4ebd) · Commits · 戴 / test

Conversion of MTRRs to ranges used the maxphyaddr from the boot CPU. This is wrong, because var_mtrr_range's mask variable then is discontiguous (like FF00FFFF000, where the first run of 0s corresponds to the bits between host and guest maxphyaddr). Instead always set up the masks to be full 64-bit values---we know that the reserved bits at the top are zero, and we can restore them when reading the MSR. This way var_mtrr_range gets a mask that just works. Fixes: Cc: qemu-stable@nongnu.org Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=107561 Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mtrr.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -300,7 +300,6 @@ static void var_mtrr_range(struct kvm_mtrr_range range, u64 start, u64 *end)
		*start = range->base & PAGE_MASK;

		mask = range->mask & PAGE_MASK;
		mask \|= ~0ULL << boot_cpu_data.x86_phys_bits;

		/* This cannot overflow because writing to the reserved bits of
		* variable MTRRs causes a #GP.
		@@ -356,10 +355,14 @@ static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
		if (var_mtrr_range_is_valid(cur))
		list_del(&mtrr_state->var_ranges[index].node);

		/* Extend the mask with all 1 bits to the left, since those
		* bits must implicitly be 0. The bits are then cleared
		* when reading them.
		*/
		if (!is_mtrr_mask)
		cur->base = data;
		else
		cur->mask = data;
		cur->mask = data \| (-1LL << cpuid_maxphyaddr(vcpu));

		/* add it to the list if it's enabled. */
		if (var_mtrr_range_is_valid(cur)) {
		@@ -426,6 +429,8 @@ int kvm_mtrr_get_msr(struct kvm_vcpu vcpu, u32 msr, u64 pdata)
		*pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
		else
		*pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;

		*pdata &= (1ULL << cpuid_maxphyaddr(vcpu)) - 1;
		}

		return 0;

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