On Tue, Oct 07, 2025 at 08:31:47AM -0500, Tom Lendacky wrote:
> On 9/25/25 05:17, Naveen N Rao (AMD) wrote:
...
> > +
> > +static void
> > +sev_snp_guest_set_tsc_frequency(Object *obj, Visitor *v, const char *name,
> > + void *opaque, Error **errp)
> > +{
> > + uint32_t value;
> > +
> > + if (!visit_type_uint32(v, name, &value, errp)) {
> > + return;
> > + }
> > +
> > + SEV_SNP_GUEST(obj)->tsc_khz = value / 1000;
>
> This will cause a value that isn't evenly divisible by 1000 to be
> rounded down, e.g.: tsc-frequency=2500000999. Should this name instead
> just be tsc-khz or secure-tsc-khz (to show it is truly associated with
> Secure TSC)?
I modeled this after the existing tsc-frequency parameter on the cpu
object to keep it simple (parameter is the same, just where it is
specified differs). This also aligns with TDX which re-uses the
tsc-frequency parameter on the cpu object.
>
> Also, I think there is already a "tsc-freq" parameter for the -cpu
> parameter (?), should there be some kind of error message if both of
> these are set? Or a warning saying it is being ignored? Or ...?
This is validated when the TSC frequency is being set on the vcpu, so I didn't
add an explicit check.
As an example, with:
-cpu EPYC-v4,tsc-frequency=2500000000 \
-object sev-snp-guest,id=sev0,cbitpos=51,reduced-phys-bits=1,secure-tsc=on
qemu-system-x86_64: warning: TSC frequency mismatch between VM (2500000 kHz)
and host (2596099 kHz), and TSC scaling unavailable
qemu-system-x86_64: kvm_init_vcpu: kvm_arch_init_vcpu failed (0): Invalid
argument
Thanks,
Naveen
