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authorPaolo Bonzini <pbonzini@redhat.com>2015-07-07 14:38:13 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2015-07-10 13:25:27 +0200
commitfd717f11015f673487ffc826e59b2bad69d20fe5 (patch)
treeea98f02afb5b24e2868861ae26b56308e3027051 /arch
parente098223b789b4a618dacd79e5e0dad4a9d5018d1 (diff)
KVM: x86: apply guest MTRR virtualization on host reserved pages
Currently guest MTRR is avoided if kvm_is_reserved_pfn returns true. However, the guest could prefer a different page type than UC for such pages. A good example is that pass-throughed VGA frame buffer is not always UC as host expected. This patch enables full use of virtual guest MTRRs. Suggested-by: Xiao Guangrong <guangrong.xiao@linux.intel.com> Tested-by: Joerg Roedel <jroedel@suse.de> (on AMD) Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/svm.c7
-rw-r--r--arch/x86/kvm/vmx.c11
2 files changed, 5 insertions, 13 deletions
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index d36cfaf5a97a..bbc678a66b18 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1166,14 +1166,11 @@ static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
u8 mtrr;
/*
- * 1. MMIO: always map as UC
+ * 1. MMIO: trust guest MTRR, so same as item 3.
* 2. No passthrough: always map as WB, and force guest PAT to WB as well
* 3. Passthrough: can't guarantee the result, try to trust guest.
*/
- if (is_mmio)
- return _PAGE_NOCACHE;
-
- if (!kvm_arch_has_assigned_device(vcpu->kvm))
+ if (!is_mmio && !kvm_arch_has_assigned_device(vcpu->kvm))
return 0;
mtrr = kvm_mtrr_get_guest_memory_type(vcpu, gfn);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e856dd566f4c..5b4e9384717a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8632,22 +8632,17 @@ static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
u64 ipat = 0;
/* For VT-d and EPT combination
- * 1. MMIO: always map as UC
+ * 1. MMIO: guest may want to apply WC, trust it.
* 2. EPT with VT-d:
* a. VT-d without snooping control feature: can't guarantee the
- * result, try to trust guest.
+ * result, try to trust guest. So the same as item 1.
* b. VT-d with snooping control feature: snooping control feature of
* VT-d engine can guarantee the cache correctness. Just set it
* to WB to keep consistent with host. So the same as item 3.
* 3. EPT without VT-d: always map as WB and set IPAT=1 to keep
* consistent with host MTRR
*/
- if (is_mmio) {
- cache = MTRR_TYPE_UNCACHABLE;
- goto exit;
- }
-
- if (!kvm_arch_has_noncoherent_dma(vcpu->kvm)) {
+ if (!is_mmio && !kvm_arch_has_noncoherent_dma(vcpu->kvm)) {
ipat = VMX_EPT_IPAT_BIT;
cache = MTRR_TYPE_WRBACK;
goto exit;