linux-kernel - Re: [RFC 01/14] x86/apic: Add new driver for Secure AVIC

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Message-ID: <8d0f9d2c-0ae4-442c-9ee4-288fd014599f@amd.com>
Date: Wed, 9 Oct 2024 07:26:55 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 dave.hansen@...ux.intel.com, Thomas.Lendacky@....com, nikunj@....com,
 Santosh.Shukla@....com, Vasant.Hegde@....com, Suravee.Suthikulpanit@....com,
 David.Kaplan@....com, x86@...nel.org, hpa@...or.com, peterz@...radead.org,
 seanjc@...gle.com, pbonzini@...hat.com, kvm@...r.kernel.org
Subject: Re: [RFC 01/14] x86/apic: Add new driver for Secure AVIC



On 10/9/2024 12:45 AM, Borislav Petkov wrote:
> On Fri, Sep 13, 2024 at 05:06:52PM +0530, Neeraj Upadhyay wrote:
>> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
>> index cd44e120fe53..ec038be0a048 100644
>> --- a/arch/x86/boot/compressed/sev.c
>> +++ b/arch/x86/boot/compressed/sev.c
>> @@ -394,6 +394,7 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
>>  				 MSR_AMD64_SNP_VMSA_REG_PROT |		\
>>  				 MSR_AMD64_SNP_RESERVED_BIT13 |		\
>>  				 MSR_AMD64_SNP_RESERVED_BIT15 |		\
>> +				 MSR_AMD64_SNP_SECURE_AVIC_ENABLED |	\
>>  				 MSR_AMD64_SNP_RESERVED_MASK)
>>  
>>  /*
> 
> Shouldn't this hunk be in the last patch of the series, after all the sAVIC
> enablement has happened?
> 

As SECURE_AVIC feature is not supported (as reported by snp_get_unsupported_features())
by guest at this patch in the series, it is added to SNP_FEATURES_IMPL_REQ here. The bit
value within SNP_FEATURES_IMPL_REQ hasn't changed with this change as the same bit pos
was part of MSR_AMD64_SNP_RESERVED_MASK before this patch. In patch 14 SECURE_AVIC guest
support is indicated by guest.


- Neeraj