linux-kernel - Re: [sos-linux-ext-patches] [PATCH] x86/sev: Ensure SVSM reserved fields are initialized to zero

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Message-ID: <4918f481-bbee-4337-870d-e62d8d2d86cf@amd.com>
Date: Mon, 18 Aug 2025 11:46:15 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Tom Lendacky <thomas.lendacky@....com>, <linux-kernel@...r.kernel.org>,
	<x86@...nel.org>
CC: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
	Michael Roth <michael.roth@....com>, Joerg Roedel <Joerg.Roedel@....com>
Subject: Re: [sos-linux-ext-patches] [PATCH] x86/sev: Ensure SVSM reserved
 fields are initialized to zero



On 8/13/2025 8:56 PM, Tom Lendacky wrote:

> In order to support future versions of the SVSM_CORE_PVALIDATE call,
> all reserved fields within a PVALIDATE entry must be set to zero as an
> SVSM should be ensuring all reserved fields are zero in order to support

Does "an SVSM" mean here an implementation like Coconut SVSM ?

> future usage of reserved areas based on the protocol version.> 
> Fixes: fcd042e86422 ("x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0")
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/boot/startup/sev-shared.c | 1 +
>  arch/x86/coco/sev/core.c           | 2 ++
>  2 files changed, 3 insertions(+)
> 
> diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
> index ac7dfd21ddd4..a34cd19796f9 100644
> --- a/arch/x86/boot/startup/sev-shared.c
> +++ b/arch/x86/boot/startup/sev-shared.c
> @@ -785,6 +785,7 @@ static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
>  	pc->entry[0].page_size = RMP_PG_SIZE_4K;
>  	pc->entry[0].action    = validate;
>  	pc->entry[0].ignore_cf = 0;
> +	pc->entry[0].rsvd      = 0;
>  	pc->entry[0].pfn       = paddr >> PAGE_SHIFT;
>  
>  	/* Protocol 0, Call ID 1 */
> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
> index 400a6ab75d45..14ef5908fb27 100644
> --- a/arch/x86/coco/sev/core.c
> +++ b/arch/x86/coco/sev/core.c
> @@ -227,6 +227,7 @@ static u64 svsm_build_ca_from_pfn_range(u64 pfn, u64 pfn_end, bool action,
>  		pe->page_size = RMP_PG_SIZE_4K;
>  		pe->action    = action;
>  		pe->ignore_cf = 0;
> +		pe->rsvd      = 0;
>  		pe->pfn       = pfn;
>  
>  		pe++;
> @@ -257,6 +258,7 @@ static int svsm_build_ca_from_psc_desc(struct snp_psc_desc *desc, unsigned int d
>  		pe->page_size = e->pagesize ? RMP_PG_SIZE_2M : RMP_PG_SIZE_4K;
>  		pe->action    = e->operation == SNP_PAGE_STATE_PRIVATE;
>  		pe->ignore_cf = 0;
> +		pe->rsvd      = 0;
>  		pe->pfn       = e->gfn;
>  
>  		pe++;
> 
> base-commit: 4c699535a3d483562354432a945a035f15dfceeb