On Mon, Jun 28, 2021 at 06:31:52PM +0100, David Edmondson wrote:
> To aid in debugging.
Please add more context to the commit message.
>
> Suggested-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> Signed-off-by: David Edmondson <david.edmondson@xxxxxxxxxx>
> ---
> arch/x86/kvm/x86.c | 23 +++++++++++++++++------
> include/uapi/linux/kvm.h | 2 ++
> 2 files changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8166ad113fb2..48ef0dc68faf 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7455,7 +7455,7 @@ 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)
> +static void prepare_emulation_failure_exit(struct kvm_vcpu *vcpu, uint64_t flags)
> {
> struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
> u32 insn_size = ctxt->fetch.end - ctxt->fetch.data;
> @@ -7466,7 +7466,8 @@ static void prepare_emulation_failure_exit(struct kvm_vcpu *vcpu)
> run->emulation_failure.ndata = 0;
> run->emulation_failure.flags = 0;
>
> - if (insn_size) {
> + if (insn_size &&
> + (flags & KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES)) {
> run->emulation_failure.ndata = 3;
> run->emulation_failure.flags |=
> KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES;
> @@ -7476,6 +7477,14 @@ static void prepare_emulation_failure_exit(struct kvm_vcpu *vcpu)
> memcpy(run->emulation_failure.insn_bytes,
> ctxt->fetch.data, insn_size);
> }
> +
> + if (flags & KVM_INTERNAL_ERROR_EMULATION_FLAG_EXIT_REASON) {
This flag is always passed so this check if superfluous. Perhaps change
`int flags` to `bool instruction_bytes` and have it control only whether
the instruction bytes are populated.
> + run->emulation_failure.ndata = 4;
> + run->emulation_failure.flags |=
> + KVM_INTERNAL_ERROR_EMULATION_FLAG_EXIT_REASON;
> + run->emulation_failure.exit_reason =
> + static_call(kvm_x86_get_exit_reason)(vcpu);
> + }
> }
>
> static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
> @@ -7492,16 +7501,18 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu, int emulation_type)
>
> if (kvm->arch.exit_on_emulation_error ||
> (emulation_type & EMULTYPE_SKIP)) {
> - prepare_emulation_failure_exit(vcpu);
> + prepare_emulation_failure_exit(
> + vcpu,
> + KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES |
> + KVM_INTERNAL_ERROR_EMULATION_FLAG_EXIT_REASON);
> return 0;
> }
>
> kvm_queue_exception(vcpu, UD_VECTOR);
>
> if (!is_guest_mode(vcpu) && static_call(kvm_x86_get_cpl)(vcpu) == 0) {
> - vcpu->run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
> - vcpu->run->internal.suberror = KVM_INTERNAL_ERROR_EMULATION;
> - vcpu->run->internal.ndata = 0;
> + prepare_emulation_failure_exit(
> + vcpu, KVM_INTERNAL_ERROR_EMULATION_FLAG_EXIT_REASON);
Should kvm_task_switch and kvm_handle_memory_failure also be updated
like this?
> return 0;
> }
>
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 68c9e6d8bbda..3e4126652a67 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -282,6 +282,7 @@ struct kvm_xen_exit {
>
> /* Flags that describe what fields in emulation_failure hold valid data. */
> #define KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES (1ULL << 0)
> +#define KVM_INTERNAL_ERROR_EMULATION_FLAG_EXIT_REASON (1ULL << 1)
>
> /* for KVM_RUN, returned by mmap(vcpu_fd, offset=0) */
> struct kvm_run {
> @@ -404,6 +405,7 @@ struct kvm_run {
> __u64 flags;
> __u8 insn_size;
> __u8 insn_bytes[15];
> + __u64 exit_reason;
Please document what this field contains, especially since its contents
depend on AMD versus Intel.
> } emulation_failure;
> /* KVM_EXIT_OSI */
> struct {
> --
> 2.30.2
>
