Re: [PATCH v6 56/60] i386/tdx: Don't treat SYSCALL as unavailable

Daniel P. Berrangé
2024-11-05T11:08:05Z

On Tue, Nov 05, 2024 at 01:24:04AM -0500, Xiaoyao Li wrote:

Preferrably explain the rationale for why this is needed in
the commit message.

> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
> target/i386/kvm/tdx.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index 9cb099e160e4..05475edf72bd 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> @@ -734,6 +734,13 @@ static int tdx_check_features(X86ConfidentialGuest *cg, CPUState *cs)
>
> requested = env->features[w];
> unavailable = requested & ~actual;
> + /*
> + * Intel enumerates SYSCALL bit as 1 only when processor in 64-bit
> + * mode and before vcpu running it's not in 64-bit mode.
> + */
> + if (w == FEAT_8000_0001_EDX && unavailable & CPUID_EXT2_SYSCALL) {
> + unavailable &= ~CPUID_EXT2_SYSCALL;
> + }
> mark_unavailable_features(cpu, w, unavailable, unav_prefix);
> if (unavailable) {
> mismatch = true;
> --
> 2.34.1
>

With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|