linux-kernel - Re: [PATCH] KVM: VMX: Flush shadow VMCS on emergency reboot

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Message-ID: <174622245784.882917.5240595687823642720.b4-ty@google.com>
Date: Fri,  2 May 2025 14:51:03 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Chao Gao <chao.gao@...el.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] KVM: VMX: Flush shadow VMCS on emergency reboot

On Mon, 24 Mar 2025 22:08:48 +0800, Chao Gao wrote:
> Ensure the shadow VMCS cache is evicted during an emergency reboot to
> prevent potential memory corruption if the cache is evicted after reboot.
> 
> This issue was identified through code inspection, as __loaded_vmcs_clear()
> flushes both the normal VMCS and the shadow VMCS.
> 
> Avoid checking the "launched" state during an emergency reboot, unlike the
> behavior in __loaded_vmcs_clear(). This is important because reboot NMIs
> can interfere with operations like copy_shadow_to_vmcs12(), where shadow
> VMCSes are loaded directly using VMPTRLD. In such cases, if NMIs occur
> right after the VMCS load, the shadow VMCSes will be active but the
> "launched" state may not be set.
> 
> [...]

Applied to kvm-x86 vmx.  I tagged it for stable, but it's not urgent (I'm 99%
certain it will never cause problems), so I figure I'd give it a full cycle in
-next.

[1/1] KVM: VMX: Flush shadow VMCS on emergency reboot
      https://github.com/kvm-x86/linux/commit/a0ee1d5faff1

--
https://github.com/kvm-x86/linux/tree/next