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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/9/24 21:02, Sean Christopherson wrote: > The folks doing TDX enabling ran into a problem where exposing a read-only > memslot to a TDX guest put it into an infinite loop. The most immediate > issue is that KVM never creates MMIO SPTEs for RO memslots, because except > for TDX (which isn't officially supported yet), such SPTEs can't distinguish > between reads and writes, i.e. would trigger MMIO on everything and thus > defeat the purpose of having a RX memslot. > > That breaks TDX, SEV-ES, and SNP, i.e. VM types that rely on MMIO caching > to reflect MMIO faults into the guest as #VC/#VE, as the guest never sees > the fault, KVM refuses to emulate, the guest loops indefinitely. That's > patch 1. > > Patches 2-4 fix an amusing number of other bugs that made it difficult to > figure out the true root cause. > > The rest is a bunch of cleanups to consolidate all of the unprotect+retry > paths (there are four-ish). > > As a bonus, adding RET_PF_WRITE_PROTECTED obviates the need for > kvm_lookup_pfn()[*]. > > [*] https://lore.kernel.org/all/63c41e25-2523-4397-96b4-557394281443@redhat.com Nice! For now I've placed it in kvm/queue as this is clearly 6.12 material. It will be replaced by the v2 of course before graduating to kvm/next. Thanks, Paolo > Sean Christopherson (22): > KVM: x86: Disallow read-only memslots for SEV-ES and SEV-SNP (and TDX) > KVM: VMX: Set PFERR_GUEST_{FINAL,PAGE}_MASK if and only if the GVA is > valid > KVM: x86/mmu: Trigger unprotect logic only on write-protection page > faults > KVM: x86/mmu: Skip emulation on page fault iff 1+ SPs were unprotected > KVM: x86: Retry to-be-emulated insn in "slow" unprotect path iff sp is > zapped > KVM: x86: Get RIP from vCPU state when storing it to last_retry_eip > KVM: x86: Store gpa as gpa_t, not unsigned long, when unprotecting for > retry > KVM: x86/mmu: Apply retry protection to "fast nTDP unprotect" path > KVM: x86/mmu: Try "unprotect for retry" iff there are indirect SPs > KVM: x86/mmu: Replace PFERR_NESTED_GUEST_PAGE with a more descriptive > helper > KVM: x86: Move EMULTYPE_ALLOW_RETRY_PF to x86_emulate_instruction() > KVM: x86: Fold retry_instruction() into x86_emulate_instruction() > KVM: x86/mmu: Don't try to unprotect an INVALID_GPA > KVM: x86/mmu: Always walk guest PTEs with WRITE access when > unprotecting > KVM: x86/mmu: Move event re-injection unprotect+retry into common path > KVM: x86: Remove manual pfn lookup when retrying #PF after failed > emulation > KVM: x86: Check EMULTYPE_WRITE_PF_TO_SP before unprotecting gfn > KVM: x86: Apply retry protection to "unprotect on failure" path > KVM: x86: Update retry protection fields when forcing retry on > emulation failure > KVM: x86: Rename > reexecute_instruction()=>kvm_unprotect_and_retry_on_failure() > KVM: x86/mmu: Subsume kvm_mmu_unprotect_page() into the and_retry() > version > KVM: x86/mmu: Detect if unprotect will do anything based on > invalid_list > > arch/x86/include/asm/kvm_host.h | 16 ++- > arch/x86/kvm/mmu/mmu.c | 175 ++++++++++++++++++++++---------- > arch/x86/kvm/mmu/mmu_internal.h | 3 + > arch/x86/kvm/mmu/mmutrace.h | 1 + > arch/x86/kvm/mmu/paging_tmpl.h | 2 +- > arch/x86/kvm/mmu/tdp_mmu.c | 6 +- > arch/x86/kvm/vmx/vmx.c | 5 +- > arch/x86/kvm/x86.c | 133 +++++++----------------- > include/linux/kvm_host.h | 7 ++ > virt/kvm/kvm_main.c | 5 +- > 10 files changed, 184 insertions(+), 169 deletions(-) > > > base-commit: 332d2c1d713e232e163386c35a3ba0c1b90df83f