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

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Message-ID: <ZyuFMtYSneOFrsvs@google.com>
Date: Wed, 6 Nov 2024 07:03:14 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Mario Limonciello <superm1@...nel.org>
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

+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?

> +	 */
> +	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
>