linux-kernel - Re: [PATCH] x86/CPU/AMD: Clear virtualized VMLOAD/VMSAVE on Zen4 client

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Message-ID: <fb72d616-dba8-410f-a377-3774aa7a5295@kernel.org>
Date: Wed, 6 Nov 2024 09:04:49 -0600
From: Mario Limonciello <superm1@...nel.org>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
 "H . Peter Anvin" <hpa@...or.com>, Nikolay Borisov <nik.borisov@...e.com>,
 Tom Lendacky <thomas.lendacky@....com>, Brijesh Singh
 <brijesh.singh@....com>,
 "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
 <linux-kernel@...r.kernel.org>, Mario Limonciello
 <mario.limonciello@....com>, kvm@...r.kernel.org
Subject: Re: [PATCH] x86/CPU/AMD: Clear virtualized VMLOAD/VMSAVE on Zen4
 client

On 11/6/2024 09:03, Sean Christopherson wrote:
> +KVM, given that this quite obviously affects KVM...
> 
> On Tue, Nov 05, 2024, Mario Limonciello wrote:
>> From: Mario Limonciello <mario.limonciello@....com>
>>
>> A number of Zen4 client SoCs advertise the ability to use virtualized
>> VMLOAD/VMSAVE, but using these instructions is reported to be a cause
>> of a random host reboot.
>>
>> These instructions aren't intended to be advertised on Zen4 client
>> so clear the capability.
>>
>> Cc: stable@...r.kernel.org
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219009
>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>> ---
>>   arch/x86/kernel/cpu/amd.c | 11 +++++++++++
>>   1 file changed, 11 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
>> index 015971adadfc7..ecd42c2b3242e 100644
>> --- a/arch/x86/kernel/cpu/amd.c
>> +++ b/arch/x86/kernel/cpu/amd.c
>> @@ -924,6 +924,17 @@ static void init_amd_zen4(struct cpuinfo_x86 *c)
>>   {
>>   	if (!cpu_has(c, X86_FEATURE_HYPERVISOR))
>>   		msr_set_bit(MSR_ZEN4_BP_CFG, MSR_ZEN4_BP_CFG_SHARED_BTB_FIX_BIT);
>> +
>> +	/*
>> +	 * These Zen4 SoCs advertise support for virtualized VMLOAD/VMSAVE
>> +	 * in some BIOS versions but they can lead to random host reboots.
> 
> Uh, CPU bug?  Erratum?

BIOS bug.  Those shouldn't have been advertised.

> 
>> +	 */
>> +	switch (c->x86_model) {
>> +	case 0x18 ... 0x1f:
>> +	case 0x60 ... 0x7f:
>> +		clear_cpu_cap(c, X86_FEATURE_V_VMSAVE_VMLOAD);
>> +		break;
>> +	}
>>   }
>>   
>>   static void init_amd_zen5(struct cpuinfo_x86 *c)
>> -- 
>> 2.43.0
>>