Messages in this thread | | | Subject | Re: [PATCH v2 1/3] KVM: x86: Add EMULTYPE_PF when emulation is triggered by a page fault | From | Xiaoyao Li <> | Date | Fri, 21 Feb 2020 10:59:21 +0800 |
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On 2/21/2020 4:11 AM, Sean Christopherson wrote: > On Wed, Feb 19, 2020 at 05:01:41PM +0800, Xiaoyao Li wrote: >> On 2/19/2020 7:03 AM, Sean Christopherson wrote: >>> Add a new emulation type flag to explicitly mark emulation related to a >>> page fault. Move the propation of the GPA into the emulator from the >>> page fault handler into x86_emulate_instruction, using EMULTYPE_PF as an >>> indicator that cr2 is valid. Similarly, don't propagate cr2 into the >>> exception.address when it's *not* valid. >>> >>> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> >>> --- >>> arch/x86/include/asm/kvm_host.h | 12 +++++++++--- >>> arch/x86/kvm/mmu/mmu.c | 10 ++-------- >>> arch/x86/kvm/x86.c | 25 +++++++++++++++++++------ >>> 3 files changed, 30 insertions(+), 17 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >>> index 4dffbc10d3f8..10c1e8f472b6 100644 >>> --- a/arch/x86/include/asm/kvm_host.h >>> +++ b/arch/x86/include/asm/kvm_host.h >>> @@ -1370,8 +1370,9 @@ extern u64 kvm_mce_cap_supported; >>> * decode the instruction length. For use *only* by >>> * kvm_x86_ops->skip_emulated_instruction() implementations. >>> * >>> - * EMULTYPE_ALLOW_RETRY - Set when the emulator should resume the guest to >>> - * retry native execution under certain conditions. >>> + * EMULTYPE_ALLOW_RETRY_PF - Set when the emulator should resume the guest to >>> + * retry native execution under certain conditions, >>> + * Can only be set in conjunction with EMULTYPE_PF. >>> * >>> * EMULTYPE_TRAP_UD_FORCED - Set when emulating an intercepted #UD that was >>> * triggered by KVM's magic "force emulation" prefix, >>> @@ -1384,13 +1385,18 @@ extern u64 kvm_mce_cap_supported; >>> * backdoor emulation, which is opt in via module param. >>> * VMware backoor emulation handles select instructions >>> * and reinjects the #GP for all other cases. >>> + * >>> + * EMULTYPE_PF - Set when emulating MMIO by way of an intercepted #PF, in which >>> + * case the CR2/GPA value pass on the stack is valid. >>> */ >>> #define EMULTYPE_NO_DECODE (1 << 0) >>> #define EMULTYPE_TRAP_UD (1 << 1) >>> #define EMULTYPE_SKIP (1 << 2) >>> -#define EMULTYPE_ALLOW_RETRY (1 << 3) >>> +#define EMULTYPE_ALLOW_RETRY_PF (1 << 3) >> >> How about naming it as EMULTYPE_PF_ALLOW_RETRY and exchanging the bit >> position with EMULTYPE_PF ? > > Hmm, EMULTYPE_PF_ALLOW_RETRY does sound better. I'm on the fence regarding > shuffling the bits. If I were to shuffle the bits, I'd do a more thorough > reorder so that the #UD and #PF types are consecutive, e.g. > > #define EMULTYPE_NO_DECODE (1 << 0) > #define EMULTYPE_TRAP_UD (1 << 1) > #define EMULTYPE_TRAP_UD_FORCED (1 << 2) > #define EMULTYPE_SKIP (1 << 3) > #define EMULTYPE_VMWARE_GP (1 << 4) > #define EMULTYPE_PF (1 << 5) > #define EMULTYPE_PF_ALLOW_RETRY (1 << 6) > > Part of me really wants to do that, the other part of me thinks it's > unnecessary thrash. >
I'm fine with thorough reorder, it helps read the codes. It's up to Paolo, anyway.
>>> #define EMULTYPE_TRAP_UD_FORCED (1 << 4) >>> #define EMULTYPE_VMWARE_GP (1 << 5) >>> +#define EMULTYPE_PF (1 << 6) >>> + >>> int kvm_emulate_instruction(struct kvm_vcpu *vcpu, int emulation_type); >>> int kvm_emulate_instruction_from_buffer(struct kvm_vcpu *vcpu, >>> void *insn, int insn_len); >>> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c >>> index 7011a4e54866..258624d46588 100644 >>> --- a/arch/x86/kvm/mmu/mmu.c >>> +++ b/arch/x86/kvm/mmu/mmu.c >>> @@ -5416,18 +5416,12 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page_virt); >>> int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code, >>> void *insn, int insn_len) >>> { >>> - int r, emulation_type = 0; >>> + int r, emulation_type = EMULTYPE_PF; >>> bool direct = vcpu->arch.mmu->direct_map; >>> if (WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root_hpa))) >>> return RET_PF_RETRY; >>> - /* With shadow page tables, fault_address contains a GVA or nGPA. */ >>> - if (vcpu->arch.mmu->direct_map) { >>> - vcpu->arch.gpa_available = true; >>> - vcpu->arch.gpa_val = cr2_or_gpa; >>> - } >>> - >>> r = RET_PF_INVALID; >>> if (unlikely(error_code & PFERR_RSVD_MASK)) { >>> r = handle_mmio_page_fault(vcpu, cr2_or_gpa, direct); >>> @@ -5472,7 +5466,7 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code, >>> * for L1 isn't going to magically fix whatever issue cause L2 to fail. >>> */ >>> if (!mmio_info_in_cache(vcpu, cr2_or_gpa, direct) && !is_guest_mode(vcpu)) >>> - emulation_type = EMULTYPE_ALLOW_RETRY; >>> + emulation_type |= EMULTYPE_ALLOW_RETRY_PF; >>> emulate: >>> /* >>> * On AMD platforms, under certain conditions insn_len may be zero on #NPF. >>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >>> index fbabb2f06273..92af6c5a69e3 100644 >>> --- a/arch/x86/kvm/x86.c >>> +++ b/arch/x86/kvm/x86.c >>> @@ -6483,10 +6483,11 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, >>> gpa_t gpa = cr2_or_gpa; >>> kvm_pfn_t pfn; >>> - if (!(emulation_type & EMULTYPE_ALLOW_RETRY)) >>> + if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF)) >>> return false; >>> - if (WARN_ON_ONCE(is_guest_mode(vcpu))) >>> + if (WARN_ON_ONCE(is_guest_mode(vcpu)) || >>> + WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF))) >>> return false; >>> if (!vcpu->arch.mmu->direct_map) { >>> @@ -6574,10 +6575,11 @@ static bool retry_instruction(struct x86_emulate_ctxt *ctxt, >>> */ >>> vcpu->arch.last_retry_eip = vcpu->arch.last_retry_addr = 0; >>> - if (!(emulation_type & EMULTYPE_ALLOW_RETRY)) >>> + if (!(emulation_type & EMULTYPE_ALLOW_RETRY_PF)) >>> return false; >>> - if (WARN_ON_ONCE(is_guest_mode(vcpu))) >>> + if (WARN_ON_ONCE(is_guest_mode(vcpu)) || >>> + WARN_ON_ONCE(!(emulation_type & EMULTYPE_PF))) >>> return false; >>> if (x86_page_table_writing_insn(ctxt)) >>> @@ -6830,8 +6832,19 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, >>> } >>> restart: >>> - /* Save the faulting GPA (cr2) in the address field */ >>> - ctxt->exception.address = cr2_or_gpa; >>> + if (emulation_type & EMULTYPE_PF) { >>> + /* Save the faulting GPA (cr2) in the address field */ >>> + ctxt->exception.address = cr2_or_gpa; >>> + >>> + /* With shadow page tables, cr2 contains a GVA or nGPA. */ >>> + if (vcpu->arch.mmu->direct_map) { >>> + vcpu->arch.gpa_available = true; >>> + vcpu->arch.gpa_val = cr2_or_gpa; >>> + } >>> + } else { >>> + /* Sanitize the address out of an abundance of paranoia. */ >>> + ctxt->exception.address = 0; >>> + } >>> r = x86_emulate_insn(ctxt); >>> >>
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