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

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Message-ID: <26004db5-431b-fd28-9497-4e48bd6096c3@amd.com>
Date: Mon, 18 Aug 2025 08:47:10 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: "Nikunj A. Dadhania" <nikunj@....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 8/18/25 01:16, Nikunj A. Dadhania wrote:
> 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 ?

Yes.

Thanks,
Tom

> 
>> 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
>