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

Mario Limonciello
2024-11-06T15:04:52Z

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@amd.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@vger.kernel.org
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219009
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.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
>>