Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'for-linus-6.11' of git://git.kernel.org/pub/scm/virt/kvm/kvm
Pull kvm fix from Paolo Bonzini:
"Do not always honor guest PAT on CPUs that support self-snoop.
This triggers an issue in the bochsdrm driver, which used ioremap()
instead of ioremap_wc() to map the video RAM.
The revert lets video RAM use the WB memory type instead of the slower
UC memory type"
* tag 'for-linus-6.11' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
Revert "KVM: VMX: Always honor guest PAT on CPUs that support self-snoop"
+7
-11
+3
-5
arch/x86/kvm/mmu/mmu.c
+3
-5
arch/x86/kvm/mmu/mmu.c
···
4674
4674
bool kvm_mmu_may_ignore_guest_pat(void)
4675
4675
{
4676
4676
/*
4677
-
* When EPT is enabled (shadow_memtype_mask is non-zero), the CPU does
4678
-
* not support self-snoop (or is affected by an erratum), and the VM
4677
+
* When EPT is enabled (shadow_memtype_mask is non-zero), and the VM
4679
4678
* has non-coherent DMA (DMA doesn't snoop CPU caches), KVM's ABI is to
4680
4679
* honor the memtype from the guest's PAT so that guest accesses to
4681
4680
* memory that is DMA'd aren't cached against the guest's wishes. As a
4682
4681
* result, KVM _may_ ignore guest PAT, whereas without non-coherent DMA,
4683
-
* KVM _always_ ignores or honors guest PAT, i.e. doesn't toggle SPTE
4684
-
* bits in response to non-coherent device (un)registration.
4682
+
* KVM _always_ ignores guest PAT (when EPT is enabled).
4685
4683
*/
4686
-
return !static_cpu_has(X86_FEATURE_SELFSNOOP) && shadow_memtype_mask;
4684
+
return shadow_memtype_mask;
4687
4685
}
4688
4686
4689
4687
int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
+4
-6
arch/x86/kvm/vmx/vmx.c
+4
-6
arch/x86/kvm/vmx/vmx.c
···
7659
7659
7660
7660
/*
7661
7661
* Force WB and ignore guest PAT if the VM does NOT have a non-coherent
7662
-
* device attached and the CPU doesn't support self-snoop. Letting the
7663
-
* guest control memory types on Intel CPUs without self-snoop may
7664
-
* result in unexpected behavior, and so KVM's (historical) ABI is to
7665
-
* trust the guest to behave only as a last resort.
7662
+
* device attached. Letting the guest control memory types on Intel
7663
+
* CPUs may result in unexpected behavior, and so KVM's ABI is to trust
7664
+
* the guest to behave only as a last resort.
7666
7665
*/
7667
-
if (!static_cpu_has(X86_FEATURE_SELFSNOOP) &&
7668
-
!kvm_arch_has_noncoherent_dma(vcpu->kvm))
7666
+
if (!kvm_arch_has_noncoherent_dma(vcpu->kvm))
7669
7667
return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT) | VMX_EPT_IPAT_BIT;
7670
7668
7671
7669
return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT);