Re: [PATCH v1 7/8] x86/sev: Allow the guest to configure interrupt vectors for the hypervisor

[Borislav Petkov]

On Sat, Aug 29, 2026 at 03:39:45AM +0000, Melody Wang wrote:
> The SVSM APIC protocol supports 5 API calls. SVSM_APIC_CONFIGURE_VECTOR
> (shortened to SVSM_APIC_CONFIG_VECTOR for brevity), call 4, provides for
> the guest to configure an interrupt vector which the guest allows and
> the hypervisor can use to signal interrupts for it.
> 
> Implement this call, and make the default interrupt setting permissive
> to allow all interrupts when detecting an SVSM and Alternate Injection
> is enabled.
> 
> Signed-off-by: Melody Wang <huibo.wang@xxxxxxx>
> ---
>  arch/x86/boot/compressed/sev.c | 12 +++++++++++-
>  arch/x86/boot/compressed/sev.h |  7 +++++++
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index a8a175c90fa8..479b74c75b4b 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -520,7 +520,10 @@ bool sev_prepare(void)
>  		return true;
>  	}
>  
> -	/* Register Alternate Injection */
> +	/* When the guest is running at VMPL2 with Alternate Injection enabled,
> +	 * register Alternate Injection, and configure all of interrupts as
> +	 * permissive by default.
> +	 */

Kernel comments style format is:

	/*
	 * A sentence ending with a full-stop.
	 * Another sentence. ...
	 * More sentences. ...
	 */

>  	if (early_is_sevsnp_guest() && snp_vmpl) {
>  		struct svsm_call call = {};
>  		int ret;
> @@ -535,6 +538,13 @@ bool sev_prepare(void)
>  		ret = svsm_call_msr_protocol(&call);
>  		if (ret)
>  			sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_ALT_INJ_FAIL);
> +
> +		call.rax = SVSM_APIC_CALL(SVSM_APIC_CONFIG_VECTOR);
> +		call.rcx = SVSM_IRQ_ENABLE_ALL;
> +
> +		ret = svsm_call_msr_protocol(&call);
> +		if (svsm_call_msr_protocol(&call))

That looks like a typo here and Sashiko is correct:

  |Does this code inadvertently execute svsm_call_msr_protocol() twice when
  |booting an SEV-SNP guest at VMPL2 with Alternate Injection enabled?

IOW:

	if (ret)


-- 
Regards/Gruss,
    Boris.

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