linux-kernel - Re: [PATCH] x86/fred: Fix early boot failures on SEV-ES/SNP guests

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Message-ID: <119df613-9138-4e90-8758-3142b4025fea@amd.com>
Date: Fri, 6 Feb 2026 17:42:00 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Dave Hansen <dave.hansen@...el.com>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>, <bp@...en8.de>, <thomas.lendacky@....com>
CC: <tglx@...nel.org>, <mingo@...hat.com>, <dave.hansen@...ux.intel.com>,
	<hpa@...or.com>, <xin@...or.com>, <seanjc@...gle.com>, <pbonzini@...hat.com>,
	<x86@...nel.org>, <jon.grimm@....com>, <stable@...r.kernel.org>
Subject: Re: [PATCH] x86/fred: Fix early boot failures on SEV-ES/SNP guests



On 2/5/2026 9:40 PM, Dave Hansen wrote:
> On 2/4/26 21:10, Nikunj A Dadhania wrote:
> ...
>> --- a/arch/x86/entry/entry_fred.c
>> +++ b/arch/x86/entry/entry_fred.c
>> @@ -208,6 +208,11 @@ static noinstr void fred_hwexc(struct pt_regs *regs, unsigned long error_code)
>>  #ifdef CONFIG_X86_CET
>>  	case X86_TRAP_CP: return exc_control_protection(regs, error_code);
>>  #endif
>> +	case X86_TRAP_VC:
>> +		if (user_mode(regs))
>> +			return user_exc_vmm_communication(regs, error_code);
>> +		else
>> +			return kernel_exc_vmm_communication(regs, error_code);
>>  	default: return fred_bad_type(regs, error_code);
>>  	}
> 
> Please look at the code in the ~20 lines above this hunk. It has a nice,
> consistent form of:
> 
> 	case X86_TRAP_FOO: return exc_foo_action(...);
> 
> Could we keep that going, please?

There are couple of options, I will test and get back.

> Second, these functions are defined in arch/x86/coco/sev/vc-handle.c.
> That looks suspiciously like CONFIG_AMD_MEM_ENCRYPT code and not
> something that will compile everywhere. Also note the other features in
> the switch() block. See all the #ifdefs on those?
> 
> Have you compiled this?

Compiled and tested. I missed testing without CONFIG_AMD_MEM_ENCRYPT, will add.

Regards,
Nikunj