| Message ID | 20210430143751.1693253-2-aaronlewis@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fallback for emulation errors | expand |
On Friday, 2021-04-30 at 07:37:50 -07, Aaron Lewis wrote: > Add a fallback mechanism to the in-kernel instruction emulator that > allows userspace the opportunity to process an instruction the emulator > was unable to. When the in-kernel instruction emulator fails to process > an instruction it will either inject a #UD into the guest or exit to > userspace with exit reason KVM_INTERNAL_ERROR. This is because it does > not know how to proceed in an appropriate manner. This feature lets > userspace get involved to see if it can figure out a better path > forward. > > Signed-off-by: Aaron Lewis <aaronlewis@google.com> Minor comment about the documentation below, but anyway... Reviewed-by: David Edmondson <david.edmondson@oracle.com> > --- > Documentation/virt/kvm/api.rst | 21 +++++++++++++++++++ > arch/x86/include/asm/kvm_host.h | 6 ++++++ > arch/x86/kvm/x86.c | 37 +++++++++++++++++++++++++++++---- > include/uapi/linux/kvm.h | 23 ++++++++++++++++++++ > tools/include/uapi/linux/kvm.h | 23 ++++++++++++++++++++ > 5 files changed, 106 insertions(+), 4 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 307f2fcf1b02..ed77835eab54 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6233,6 +6233,27 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them. > This capability can be used to check / enable 2nd DAWR feature provided > by POWER10 processor. > > +7.24 KVM_CAP_EXIT_ON_EMULATION_FAILURE > +-------------------------------------- > + > +:Architectures: x86 > +:Parameters: args[0] whether the feature should be enabled or not > + > +When this capability is enabled the in-kernel instruction emulator packs > +the exit struct of KVM_INTERNAL_ERROR with the instruction length and > +instruction bytes when an error occurs while emulating an instruction. This > +will also happen when the emulation type is set to EMULTYPE_SKIP, but with this > +capability enabled this becomes the default behavior regarless of how the s/regarless/regardless/ > +emulation type is set unless it is a VMware #GP; in that case a #GP is injected > +and KVM does not exit to userspace. > + > +When this capability is enabled use the emulation_failure struct instead of the > +internal struct for the exit struct. They have the same layout, but the > +emulation_failure struct matches the content better. It also explicitly defines > +the 'flags' field which is used to describe the fields in the struct that are > +valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is set in the > +'flags' field then 'insn_size' and 'insn_bytes' has valid data in them.) Starting both paragraphs with "With this capability enabled..." would probably cause me to stop reading if I didn't enable the capability, but as the first paragraph goes on to say, EMULTYPE_SKIP will also cause the instruction to be provided. > 8. Other capabilities. > ====================== > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 3768819693e5..07235d08e976 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -1049,6 +1049,12 @@ struct kvm_arch { > bool exception_payload_enabled; > > bool bus_lock_detection_enabled; > + /* > + * If exit_on_emulation_error is set, and the in-kernel instruction > + * emulator fails to emulate an instruction, allow userspace > + * the opportunity to look at it. > + */ > + bool exit_on_emulation_error; > > /* Deflect RDMSR and WRMSR to user space when they trigger a #GP */ > u32 user_space_msr_mask; > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index eca63625aee4..703bcc93b129 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -3771,6 +3771,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) > case KVM_CAP_X86_USER_SPACE_MSR: > case KVM_CAP_X86_MSR_FILTER: > case KVM_CAP_ENFORCE_PV_FEATURE_CPUID: > + case KVM_CAP_EXIT_ON_EMULATION_FAILURE: > r = 1; > break; > #ifdef CONFIG_KVM_XEN > @@ -5357,6 +5358,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > kvm->arch.bus_lock_detection_enabled = true; > r = 0; > break; > + case KVM_CAP_EXIT_ON_EMULATION_FAILURE: > + kvm->arch.exit_on_emulation_error = cap->args[0]; > + r = 0; > + break; > default: > r = -EINVAL; > break; > @@ -7119,8 +7124,33 @@ void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip) > } > EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt); > > +static void prepare_emulation_failure_exit(struct kvm_vcpu *vcpu) > +{ > + struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt; > + u32 insn_size = ctxt->fetch.end - ctxt->fetch.data; > + struct kvm_run *run = vcpu->run; > + > + run->exit_reason = KVM_EXIT_INTERNAL_ERROR; > + run->emulation_failure.suberror = KVM_INTERNAL_ERROR_EMULATION; > + run->emulation_failure.ndata = 0; > + run->emulation_failure.flags = 0; > + > + if (insn_size) { > + run->emulation_failure.ndata = 3; > + run->emulation_failure.flags |= > + KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES; > + run->emulation_failure.insn_size = insn_size; > + memset(run->emulation_failure.insn_bytes, 0x90, > + sizeof(run->emulation_failure.insn_bytes)); > + memcpy(run->emulation_failure.insn_bytes, > + ctxt->fetch.data, insn_size); > + } > +} > + > static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type) > { > + struct kvm *kvm = vcpu->kvm; > + > ++vcpu->stat.insn_emulation_fail; > trace_kvm_emulate_insn_failed(vcpu); > > @@ -7129,10 +7159,9 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type) > return 1; > } > > - if (emulation_type & EMULTYPE_SKIP) { > - vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; > - vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; > - vcpu->run->internal.ndata = 0; > + if (kvm->arch.exit_on_emulation_error || > + (emulation_type & EMULTYPE_SKIP)) { > + prepare_emulation_failure_exit(vcpu); > return 0; > } > > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index f6afee209620..1bca5d066e3c 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -279,6 +279,9 @@ struct kvm_xen_exit { > /* Encounter unexpected vm-exit reason */ > #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4 > > +/* Flags that describe what fields in emulation_failure hold valid data. */ > +#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0) > + > /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ > struct kvm_run { > /* in */ > @@ -382,6 +385,25 @@ struct kvm_run { > __u32 ndata; > __u64 data[16]; > } internal; > + /* > + * KVM_INTERNAL_ERROR_EMULATION > + * > + * "struct emulation_failure" is an overlay of "struct internal" > + * that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of > + * KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error > + * sub-types, this struct is ABI! It also needs to be backwards > + * compatible with "struct internal". Take special care that > + * "ndata" is correct, that new fields are enumerated in "flags", > + * and that each flag enumerates fields that are 64-bit aligned > + * and sized (so that ndata+internal.data[] is valid/accurate). > + */ > + struct { > + __u32 suberror; > + __u32 ndata; > + __u64 flags; > + __u8 insn_size; > + __u8 insn_bytes[15]; > + } emulation_failure; > /* KVM_EXIT_OSI */ > struct { > __u64 gprs[32]; > @@ -1078,6 +1100,7 @@ struct kvm_ppc_resize_hpt { > #define KVM_CAP_DIRTY_LOG_RING 192 > #define KVM_CAP_X86_BUS_LOCK_EXIT 193 > #define KVM_CAP_PPC_DAWR1 194 > +#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 195 > > #ifdef KVM_CAP_IRQ_ROUTING > > diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h > index f6afee209620..1bca5d066e3c 100644 > --- a/tools/include/uapi/linux/kvm.h > +++ b/tools/include/uapi/linux/kvm.h > @@ -279,6 +279,9 @@ struct kvm_xen_exit { > /* Encounter unexpected vm-exit reason */ > #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4 > > +/* Flags that describe what fields in emulation_failure hold valid data. */ > +#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0) > + > /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ > struct kvm_run { > /* in */ > @@ -382,6 +385,25 @@ struct kvm_run { > __u32 ndata; > __u64 data[16]; > } internal; > + /* > + * KVM_INTERNAL_ERROR_EMULATION > + * > + * "struct emulation_failure" is an overlay of "struct internal" > + * that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of > + * KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error > + * sub-types, this struct is ABI! It also needs to be backwards > + * compatible with "struct internal". Take special care that > + * "ndata" is correct, that new fields are enumerated in "flags", > + * and that each flag enumerates fields that are 64-bit aligned > + * and sized (so that ndata+internal.data[] is valid/accurate). > + */ > + struct { > + __u32 suberror; > + __u32 ndata; > + __u64 flags; > + __u8 insn_size; > + __u8 insn_bytes[15]; > + } emulation_failure; > /* KVM_EXIT_OSI */ > struct { > __u64 gprs[32]; > @@ -1078,6 +1100,7 @@ struct kvm_ppc_resize_hpt { > #define KVM_CAP_DIRTY_LOG_RING 192 > #define KVM_CAP_X86_BUS_LOCK_EXIT 193 > #define KVM_CAP_PPC_DAWR1 194 > +#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 195 > > #ifdef KVM_CAP_IRQ_ROUTING > > -- > 2.31.1.527.g47e6f16901-goog dme.
> > +7.24 KVM_CAP_EXIT_ON_EMULATION_FAILURE > > +-------------------------------------- > > + > > +:Architectures: x86 > > +:Parameters: args[0] whether the feature should be enabled or not > > + > > +When this capability is enabled the in-kernel instruction emulator packs > > +the exit struct of KVM_INTERNAL_ERROR with the instruction length and > > +instruction bytes when an error occurs while emulating an instruction. This > > +will also happen when the emulation type is set to EMULTYPE_SKIP, but with this > > +capability enabled this becomes the default behavior regarless of how the > > s/regarless/regardless/ > > > +emulation type is set unless it is a VMware #GP; in that case a #GP is injected > > +and KVM does not exit to userspace. > > + > > +When this capability is enabled use the emulation_failure struct instead of the > > +internal struct for the exit struct. They have the same layout, but the > > +emulation_failure struct matches the content better. It also explicitly defines > > +the 'flags' field which is used to describe the fields in the struct that are > > +valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is set in the > > +'flags' field then 'insn_size' and 'insn_bytes' has valid data in them.) > > Starting both paragraphs with "With this capability enabled..." would > probably cause me to stop reading if I didn't enable the capability, but > as the first paragraph goes on to say, EMULTYPE_SKIP will also cause the > instruction to be provided. > What about this instead? When this capability is enabled, an emulation failure will result in an exit to userspace with KVM_INTERNAL_ERROR (except when the emulator was invoked to handle a VMware backdoor instruction). Furthermore, KVM will now provide up to 15 instruction bytes for any exit to userspace resulting from an emulation failure. When these exits to userspace occur use the emulation_failure struct instead of the internal struct. They both have the same layout, but the emulation_failure struct matches the content better. It also explicitly defines the 'flags' field which is used to describe the fields in the struct that are valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is set in the 'flags' field then both 'insn_size' and 'insn_bytes' have valid data in them.) I left out the part about EMULTYPE_SKIP because that behavior is not affected by setting KVM_CAP_EXIT_ON_EMULATION_FAILURE, so I thought it wasn't needed in the documentation here.
On Friday, 2021-05-07 at 07:27:07 -07, Aaron Lewis wrote: >> > +7.24 KVM_CAP_EXIT_ON_EMULATION_FAILURE >> > +-------------------------------------- >> > + >> > +:Architectures: x86 >> > +:Parameters: args[0] whether the feature should be enabled or not >> > + >> > +When this capability is enabled the in-kernel instruction emulator packs >> > +the exit struct of KVM_INTERNAL_ERROR with the instruction length and >> > +instruction bytes when an error occurs while emulating an instruction. This >> > +will also happen when the emulation type is set to EMULTYPE_SKIP, but with this >> > +capability enabled this becomes the default behavior regarless of how the >> >> s/regarless/regardless/ >> >> > +emulation type is set unless it is a VMware #GP; in that case a #GP is injected >> > +and KVM does not exit to userspace. >> > + >> > +When this capability is enabled use the emulation_failure struct instead of the >> > +internal struct for the exit struct. They have the same layout, but the >> > +emulation_failure struct matches the content better. It also explicitly defines >> > +the 'flags' field which is used to describe the fields in the struct that are >> > +valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is set in the >> > +'flags' field then 'insn_size' and 'insn_bytes' has valid data in them.) >> >> Starting both paragraphs with "With this capability enabled..." would >> probably cause me to stop reading if I didn't enable the capability, but >> as the first paragraph goes on to say, EMULTYPE_SKIP will also cause the >> instruction to be provided. >> > > What about this instead? Reads better to me, thanks. > When this capability is enabled, an emulation failure will result in an exit > to userspace with KVM_INTERNAL_ERROR (except when the emulator was invoked > to handle a VMware backdoor instruction). Furthermore, KVM will now provide up > to 15 instruction bytes for any exit to userspace resulting from an emulation > failure. When these exits to userspace occur use the emulation_failure struct > instead of the internal struct. They both have the same layout, but the > emulation_failure struct matches the content better. It also explicitly > defines the 'flags' field which is used to describe the fields in the struct > that are valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is > set in the 'flags' field then both 'insn_size' and 'insn_bytes' have valid data > in them.) > > I left out the part about EMULTYPE_SKIP because that behavior is not > affected by setting KVM_CAP_EXIT_ON_EMULATION_FAILURE, so I thought it > wasn't needed in the documentation here. dme.
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 307f2fcf1b02..ed77835eab54 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6233,6 +6233,27 @@ KVM_RUN_BUS_LOCK flag is used to distinguish between them. This capability can be used to check / enable 2nd DAWR feature provided by POWER10 processor. +7.24 KVM_CAP_EXIT_ON_EMULATION_FAILURE +-------------------------------------- + +:Architectures: x86 +:Parameters: args[0] whether the feature should be enabled or not + +When this capability is enabled the in-kernel instruction emulator packs +the exit struct of KVM_INTERNAL_ERROR with the instruction length and +instruction bytes when an error occurs while emulating an instruction. This +will also happen when the emulation type is set to EMULTYPE_SKIP, but with this +capability enabled this becomes the default behavior regarless of how the +emulation type is set unless it is a VMware #GP; in that case a #GP is injected +and KVM does not exit to userspace. + +When this capability is enabled use the emulation_failure struct instead of the +internal struct for the exit struct. They have the same layout, but the +emulation_failure struct matches the content better. It also explicitly defines +the 'flags' field which is used to describe the fields in the struct that are +valid (ie: if KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES is set in the +'flags' field then 'insn_size' and 'insn_bytes' has valid data in them.) + 8. Other capabilities. ====================== diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 3768819693e5..07235d08e976 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1049,6 +1049,12 @@ struct kvm_arch { bool exception_payload_enabled; bool bus_lock_detection_enabled; + /* + * If exit_on_emulation_error is set, and the in-kernel instruction + * emulator fails to emulate an instruction, allow userspace + * the opportunity to look at it. + */ + bool exit_on_emulation_error; /* Deflect RDMSR and WRMSR to user space when they trigger a #GP */ u32 user_space_msr_mask; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index eca63625aee4..703bcc93b129 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3771,6 +3771,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_X86_USER_SPACE_MSR: case KVM_CAP_X86_MSR_FILTER: case KVM_CAP_ENFORCE_PV_FEATURE_CPUID: + case KVM_CAP_EXIT_ON_EMULATION_FAILURE: r = 1; break; #ifdef CONFIG_KVM_XEN @@ -5357,6 +5358,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, kvm->arch.bus_lock_detection_enabled = true; r = 0; break; + case KVM_CAP_EXIT_ON_EMULATION_FAILURE: + kvm->arch.exit_on_emulation_error = cap->args[0]; + r = 0; + break; default: r = -EINVAL; break; @@ -7119,8 +7124,33 @@ void kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip) } EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt); +static void prepare_emulation_failure_exit(struct kvm_vcpu *vcpu) +{ + struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt; + u32 insn_size = ctxt->fetch.end - ctxt->fetch.data; + struct kvm_run *run = vcpu->run; + + run->exit_reason = KVM_EXIT_INTERNAL_ERROR; + run->emulation_failure.suberror = KVM_INTERNAL_ERROR_EMULATION; + run->emulation_failure.ndata = 0; + run->emulation_failure.flags = 0; + + if (insn_size) { + run->emulation_failure.ndata = 3; + run->emulation_failure.flags |= + KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES; + run->emulation_failure.insn_size = insn_size; + memset(run->emulation_failure.insn_bytes, 0x90, + sizeof(run->emulation_failure.insn_bytes)); + memcpy(run->emulation_failure.insn_bytes, + ctxt->fetch.data, insn_size); + } +} + static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type) { + struct kvm *kvm = vcpu->kvm; + ++vcpu->stat.insn_emulation_fail; trace_kvm_emulate_insn_failed(vcpu); @@ -7129,10 +7159,9 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type) return 1; } - if (emulation_type & EMULTYPE_SKIP) { - vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR; - vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION; - vcpu->run->internal.ndata = 0; + if (kvm->arch.exit_on_emulation_error || + (emulation_type & EMULTYPE_SKIP)) { + prepare_emulation_failure_exit(vcpu); return 0; } diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index f6afee209620..1bca5d066e3c 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -279,6 +279,9 @@ struct kvm_xen_exit { /* Encounter unexpected vm-exit reason */ #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4 +/* Flags that describe what fields in emulation_failure hold valid data. */ +#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0) + /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ struct kvm_run { /* in */ @@ -382,6 +385,25 @@ struct kvm_run { __u32 ndata; __u64 data[16]; } internal; + /* + * KVM_INTERNAL_ERROR_EMULATION + * + * "struct emulation_failure" is an overlay of "struct internal" + * that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of + * KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error + * sub-types, this struct is ABI! It also needs to be backwards + * compatible with "struct internal". Take special care that + * "ndata" is correct, that new fields are enumerated in "flags", + * and that each flag enumerates fields that are 64-bit aligned + * and sized (so that ndata+internal.data[] is valid/accurate). + */ + struct { + __u32 suberror; + __u32 ndata; + __u64 flags; + __u8 insn_size; + __u8 insn_bytes[15]; + } emulation_failure; /* KVM_EXIT_OSI */ struct { __u64 gprs[32]; @@ -1078,6 +1100,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_DIRTY_LOG_RING 192 #define KVM_CAP_X86_BUS_LOCK_EXIT 193 #define KVM_CAP_PPC_DAWR1 194 +#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 195 #ifdef KVM_CAP_IRQ_ROUTING diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h index f6afee209620..1bca5d066e3c 100644 --- a/tools/include/uapi/linux/kvm.h +++ b/tools/include/uapi/linux/kvm.h @@ -279,6 +279,9 @@ struct kvm_xen_exit { /* Encounter unexpected vm-exit reason */ #define KVM_INTERNAL_ERROR_UNEXPECTED_EXIT_REASON 4 +/* Flags that describe what fields in emulation_failure hold valid data. */ +#define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0) + /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */ struct kvm_run { /* in */ @@ -382,6 +385,25 @@ struct kvm_run { __u32 ndata; __u64 data[16]; } internal; + /* + * KVM_INTERNAL_ERROR_EMULATION + * + * "struct emulation_failure" is an overlay of "struct internal" + * that is used for the KVM_INTERNAL_ERROR_EMULATION sub-type of + * KVM_EXIT_INTERNAL_ERROR. Note, unlike other internal error + * sub-types, this struct is ABI! It also needs to be backwards + * compatible with "struct internal". Take special care that + * "ndata" is correct, that new fields are enumerated in "flags", + * and that each flag enumerates fields that are 64-bit aligned + * and sized (so that ndata+internal.data[] is valid/accurate). + */ + struct { + __u32 suberror; + __u32 ndata; + __u64 flags; + __u8 insn_size; + __u8 insn_bytes[15]; + } emulation_failure; /* KVM_EXIT_OSI */ struct { __u64 gprs[32]; @@ -1078,6 +1100,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_DIRTY_LOG_RING 192 #define KVM_CAP_X86_BUS_LOCK_EXIT 193 #define KVM_CAP_PPC_DAWR1 194 +#define KVM_CAP_EXIT_ON_EMULATION_FAILURE 195 #ifdef KVM_CAP_IRQ_ROUTING
Add a fallback mechanism to the in-kernel instruction emulator that allows userspace the opportunity to process an instruction the emulator was unable to. When the in-kernel instruction emulator fails to process an instruction it will either inject a #UD into the guest or exit to userspace with exit reason KVM_INTERNAL_ERROR. This is because it does not know how to proceed in an appropriate manner. This feature lets userspace get involved to see if it can figure out a better path forward. Signed-off-by: Aaron Lewis <aaronlewis@google.com> --- Documentation/virt/kvm/api.rst | 21 +++++++++++++++++++ arch/x86/include/asm/kvm_host.h | 6 ++++++ arch/x86/kvm/x86.c | 37 +++++++++++++++++++++++++++++---- include/uapi/linux/kvm.h | 23 ++++++++++++++++++++ tools/include/uapi/linux/kvm.h | 23 ++++++++++++++++++++ 5 files changed, 106 insertions(+), 4 deletions(-)