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[RFC,v2,15/22] KVM: X86: Handle private MMIO as shared

Message ID 20250218111017.491719-16-aik@amd.com
State New
Headers show
Series [RFC,v2,01/22] pci/doe: Define protocol types and make those public | expand

Commit Message

Alexey Kardashevskiy Feb. 18, 2025, 11:10 a.m. UTC 
Currently private MMIO nested page faults are not expected so when such
fault occurs, KVM tries moving the faulted page from private to shared
which is not going to work as private MMIO is not backed by memfd.

Handle private MMIO as shared: skip page state change and memfd
page state tracking.

The MMIO KVM memory slot is still marked as shared as the guest can
access it as private or shared so marking the MMIO slot as private
is not going to help.

Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
---
 arch/x86/kvm/mmu/mmu.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
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Patch

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 74c20dbb92da..32e27080b1c7 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4347,7 +4347,11 @@  static int __kvm_mmu_faultin_pfn(struct kvm_vcpu *vcpu,
 {
 	unsigned int foll = fault->write ? FOLL_WRITE : 0;
 
-	if (fault->is_private)
+	if (fault->slot && fault->is_private && !kvm_slot_can_be_private(fault->slot) &&
+	    (vcpu->kvm->arch.vm_type == KVM_X86_SNP_VM))
+		pr_warn("%s: private SEV TIO MMIO fault for fault->gfn=%llx\n",
+			__func__, fault->gfn);
+	else if (fault->is_private)
 		return kvm_mmu_faultin_pfn_private(vcpu, fault);
 
 	foll |= FOLL_NOWAIT;