Re: [PATCH 6/7] x86/sev: Register the guest with the SVSM APIC protocol

[Melody Wang]

Hi Tom,

On 7/31/26 12:18 PM, Tom Lendacky wrote:
> On 7/29/26 20:48, Melody Wang wrote:
> > The SVSM APIC protocol supports 5 calls. SVSM_APIC_CONFIGURE_EMULATION
> > (shortened to SVSM_APIC_CONFIG_EMULATION for brevity), call 1, provides
> > the controls whether the guest can make use of the SVSM APIC protocol.
> >
> > Implement this call, and register Alternate Injection for the guest
> > by default.
> >
> > Signed-off-by: Melody Wang <huibo.wang@xxxxxxx>
> > ---
> >   arch/x86/boot/compressed/sev.c | 17 +++++++++++++++++
> >   arch/x86/boot/compressed/sev.h |  6 ++++++
> >   2 files changed, 23 insertions(+)
> >
> > diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> > index 655291a03dcc..a98185b3869a 100644
> > --- a/arch/x86/boot/compressed/sev.c
> > +++ b/arch/x86/boot/compressed/sev.c
> > @@ -518,5 +518,22 @@ u64 sev_prepare(void)
> >   	if (unsupported)
> >   		return unsupported;
> >   
> > +	/* Register Alternate Injection */
> > +	if (early_is_sevsnp_guest() && snp_vmpl) {
> > +		struct svsm_call call = {};
> > +		int ret;
> > +
> > +		if (!(sev_get_status() & MSR_AMD64_SNP_ALTERNATE_INJ))
> > +			return 0;
> > +
> > +		call.caa = (struct svsm_ca *)boot_svsm_caa_pa;
> > +		call.rax = SVSM_APIC_CALL(SVSM_APIC_CONFIG_EMULATION);
> > +		call.rcx = SVSM_AI_REGISTER;
> > +
> > +		ret = svsm_call_msr_protocol(&call);
> > +		if (ret)
> > +			sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
>
> Shouldn't this really be where the permissive setting of allowing all
> interrupts be done, too, instead of where it is done in patch #3?

Yes, I think it makes sense to allow all of interrupts right after 
registering the SVSM APIC protocol because this is just another SVSM 
call that is going to happen and I don't see anything wrong with doing 
that there.

I did run it and it works so my next revision will have it.

Thanks,
Melody
> Thanks,
> Tom