Re: [PATCH v8 28/55] i386/tdx: Handle KVM_SYSTEM_EVENT_TDX_FATAL

[Zhao Liu <zhao1.liu@intel.com>]

On Tue, Apr 01, 2025 at 09:01:38AM -0400, Xiaoyao Li wrote:
> Date: Tue,  1 Apr 2025 09:01:38 -0400
> From: Xiaoyao Li <xiaoyao.li@intel.com>
> Subject: [PATCH v8 28/55] i386/tdx: Handle KVM_SYSTEM_EVENT_TDX_FATAL
> X-Mailer: git-send-email 2.34.1
> 
> TD guest can use TDG.VP.VMCALL<REPORT_FATAL_ERROR> to request
> termination. KVM translates such request into KVM_EXIT_SYSTEM_EVENT with
> type of KVM_SYSTEM_EVENT_TDX_FATAL.
> 
> Add hanlder for such exit. Parse and print the error message, and
> terminate the TD guest in the handler.
> 
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
> Changes in v8:
>  - update to the new data ABI of KVM_SYSTEM_EVENT_TDX_FATAL;
> 
> Changes in v6:
>  - replace the patch " i386/tdx: Handle TDG.VP.VMCALL<REPORT_FATAL_ERROR>"
>    in v5;
> ---
>  target/i386/kvm/kvm.c      | 10 +++++++++
>  target/i386/kvm/tdx-stub.c |  5 +++++
>  target/i386/kvm/tdx.c      | 45 ++++++++++++++++++++++++++++++++++++++
>  target/i386/kvm/tdx.h      |  2 ++
>  4 files changed, 62 insertions(+)
> 
> diff --git a/target/i386/kvm/kvm.c b/target/i386/kvm/kvm.c
> index 7de5014051eb..a76f34537908 100644
> --- a/target/i386/kvm/kvm.c
> +++ b/target/i386/kvm/kvm.c
> @@ -6128,6 +6128,16 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
>      case KVM_EXIT_HYPERCALL:
>          ret = kvm_handle_hypercall(run);
>          break;
> +    case KVM_EXIT_SYSTEM_EVENT:
> +        switch (run->system_event.type) {
> +        case KVM_SYSTEM_EVENT_TDX_FATAL:
> +            ret = tdx_handle_report_fatal_error(cpu, run);
> +            break;
> +        default:
> +            ret = -1;
> +            break;
> +        }
> +        break;
>      default:
>          fprintf(stderr, "KVM: unknown exit reason %d\n", run->exit_reason);
>          ret = -1;
> diff --git a/target/i386/kvm/tdx-stub.c b/target/i386/kvm/tdx-stub.c
> index 7748b6d0a446..720a4ff046ee 100644
> --- a/target/i386/kvm/tdx-stub.c
> +++ b/target/i386/kvm/tdx-stub.c
> @@ -13,3 +13,8 @@ int tdx_parse_tdvf(void *flash_ptr, int size)
>  {
>      return -EINVAL;
>  }
> +
> +int tdx_handle_report_fatal_error(X86CPU *cpu, struct kvm_run *run)
> +{
> +    return -EINVAL;
> +}
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index f8953f598584..74b7e3ac85fe 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> @@ -607,6 +607,51 @@ int tdx_parse_tdvf(void *flash_ptr, int size)
>      return tdvf_parse_metadata(&tdx_guest->tdvf, flash_ptr, size);
>  }
>  
> +int tdx_handle_report_fatal_error(X86CPU *cpu, struct kvm_run *run)
> +{
> +    uint64_t error_code = run->system_event.data[R_R12];
> +    uint64_t reg_mask = run->system_event.data[R_ECX];
> +    char *message = NULL;
> +    uint64_t *tmp;
> +
> +    if (error_code & 0xffff) {
> +        error_report("TDX: REPORT_FATAL_ERROR: invalid error code: 0x%lx",
> +                     error_code);
> +        return -1;
> +    }
> +
> +/*
> + * Only 8 registers can contain valid ASCII byte stream to form the fatal
> + * message, and their sequence is: R14, R15, RBX, RDI, RSI, R8, R9, RDX
> + */
> +#define TDX_FATAL_MESSAGE_MAX        64

At least, for this macro, and TDX_REPORT_FATAL_ERROR_GPA_VALID in later
patch, could we move these simple macro definitions out of the function?

This could improve the readability for this one function.

> +    if (reg_mask) {
> +        message = g_malloc0(TDX_FATAL_MESSAGE_MAX + 1);
> +        tmp = (uint64_t *)message;
> +
> +#define COPY_REG(REG)                               \
> +    do {                                            \
> +        if (reg_mask & BIT_ULL(REG)) {              \
> +            *(tmp++) = run->system_event.data[REG]; \
> +        }                                           \
> +    } while (0)
> +
> +        COPY_REG(R_R14);
> +        COPY_REG(R_R15);
> +        COPY_REG(R_EBX);
> +        COPY_REG(R_EDI);
> +        COPY_REG(R_ESI);
> +        COPY_REG(R_R8);
> +        COPY_REG(R_R9);
> +        COPY_REG(R_EDX);
> +        *((char *)tmp) = '\0';
> +    }
> +#undef COPY_REG
> +
> +    error_report("TD guest reports fatal error. %s", message ? : "");
> +    return -1;
> +}
> +

Otherwise,

Reviewed-by: Zhao Liu <zhao1.liu@intel.com>