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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d45f3dd8-ecda-442d-be14-529ebd2305ca@amd.com>
Date: Thu, 5 Feb 2026 11:54:00 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Greg KH <gregkh@...uxfoundation.org>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>, <bp@...en8.de>,
	<thomas.lendacky@....com>, <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 11:26 AM, Greg KH wrote:
> On Thu, Feb 05, 2026 at 05:10:30AM +0000, Nikunj A Dadhania wrote:
>> @@ -70,6 +67,17 @@ void cpu_init_fred_exceptions(void)
>>  	/* Use int $0x80 for 32-bit system calls in FRED mode */
>>  	setup_clear_cpu_cap(X86_FEATURE_SYSFAST32);
>>  	setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
>> +
>> +	/*
>> +	 * For secondary processors, FRED bit in CR4 gets enabled in cr4_init()
>> +	 * and FRED MSRs are not configured till the end of this function. For
>> +	 * SEV-ES and SNP guests, any console write before the FRED MSRs are
>> +	 * setup will cause a #VC and cannot be handled. Move the pr_info to
>> +	 * the end of this function.
>> +	 *
>> +	 * When FRED is enabled by default, remove this log message
>> +	 */
>> +	pr_info("Initialized FRED on CPU%d\n", smp_processor_id());
> 
> Did you forget to fix this up?

I didn't forget, I have moved the message to the end of cpu_init_fred_exceptions()
because the original placement triggered #VC exceptions on SEV-ES/SNP guests before
FRED MSRs were configured, causing boot failures.

> Also, when the kernel is working properly, it is quiet, so why is this
> log message needed?
> 
> thanks,
> 
> greg k-h