linux-kernel - Re: [GIT PULL] KVM: x86: VMX changes for 6.17

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Message-ID: <CABgObfZmn03eQU9XYnFRKfHWNUx006z_4x8Z91hapVHZupUYwA@mail.gmail.com>
Date: Wed, 30 Jul 2025 19:55:48 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] KVM: x86: VMX changes for 6.17

On Tue, Jul 29, 2025 at 9:44 PM Sean Christopherson <seanjc@...gle.com> wrote:
> As for this pull request, I vote to drop it for 6.17 and give ourselves time to
> figure out what we want to do with vm_dead.

Ah ok, so my spidey sense wasn't right for the wrong reasons. :)

> I want to land "terminate VM" in
> some form by 6.18 (as the next LTS), but AFAIK there's no rush to get it into
> 6.17.

As you prefer! I had already rewritten slightly the commit log, so
here it is for
your reference and future consumption:

Add a TDX sub-ioctl, KVM_TDX_TERMINATE_VM, to solve a performance
issue in TDX VM cleanup. A guest_memfd keeps a reference to the
virtual machine, which means the VM cannot be fully destroyed until
the guest_memfd is released. However, to release the guest_memfd the
TDX module must first destroy the Secure EPT, which is a slow
operation if
performed while the VM is still valid.  KVM_TDX_TERMINATE_VM allows
userspace to initiate the transition to the TEARDOWN state before file
descriptors are closed (either by hand or on process exit). The TDX
module then releases the HKID and S-EPT destruction can runup to 10x
faster.

Thanks,

Paolo