Re: [PATCH 3/3] KVM: SEV: remove ghcb variable declarations

[Tom Lendacky]

On 8/4/23 12:33, Paolo Bonzini wrote:
> To avoid possible time-of-check/time-of-use issues, the GHCB should
> almost never be accessed outside dump_ghcb, sev_es_sync_to_ghcb
> and sev_es_sync_from_ghcb.  The only legitimate uses are to set the
> exitinfo fields and to find the address of the scratch area embedded
> in the ghcb.  Accessing ghcb_usage also goes through svm->sev_es.ghcb
> in sev_es_validate_vmgexit(), but that is because anyway the value is
> not used.
>
> Removing a shortcut variable that contains the value of svm->sev_es.ghcb
> makes these cases a bit more verbose, but it limits the chance of someone
> reading the ghcb by mistake.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

> ---
>   arch/x86/kvm/svm/sev.c | 30 ++++++++++++------------------
>   1 file changed, 12 insertions(+), 18 deletions(-)