linux-kernel - Re: [GIT PULL] KVM: Device assignment accounting changes for 6.17

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Message-ID: <CABgObfay+-c+xdqA16Df-D1QzzwWry5JAjoZtF2oescoismUDg@mail.gmail.com>
Date: Mon, 28 Jul 2025 17:08:35 +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: Device assignment accounting changes for 6.17

On Sat, Jul 26, 2025 at 12:07 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Two changes that depend on the IRQ and MMIO State Data pull requests, to kill
> off kvm_arch_{start,end}_assignment().
>
> Note!  To generate the pull request, I used the result of a local merge of
> kvm/next with kvm-x86-irqs-6.17 and kvm-x86-mmio-6.17.  The resulting shortlog
> matches my expectations (and intentions), but the diff stats showed all of the
> changes from kvm-x86-irqs-6.17, and I couldn't for the life of me figure out
> how to coerce git into behaving as I want.
>
> AFAICT, it's just a cosmetic display error, there aren't any duplicate commits
> or anything.  So, rather that copy+paste those weird diff stats, I locally
> processed _this_ merge too, and then manually generated the stats with
> `git diff --stat base..HEAD`.

Yep, that happens. Not enough to consider writing a replacement for
git-request-pull, but it happens...

For me the problems are usually due to back-merges from Linus's tree
(mostly unintentional, like if arch1 uses rc2 as the base and arch2
uses rc4), so I just do a final merge from Linus's tree and use the
*reverse* of that commit's diffstat (git diff --stat HEAD HEAD^) for
the pull request.

Paolo

> The following changes since <the result of the aforementioned merges>:
>
>   KVM: VMX: Apply MMIO Stale Data mitigation if KVM maps MMIO into the guest (2025-06-25 08:42:51 -0700)
>
> are available in the Git repository at:
>
>   https://github.com/kvm-x86/linux.git tags/kvm-x86-no_assignment-6.17
>
> for you to fetch changes up to bbc13ae593e0ea47357ff6e4740c533c16c2ae1e:
>
>   VFIO: KVM: x86: Drop kvm_arch_{start,end}_assignment() (2025-06-25 09:51:33 -0700)
>
> ----------------------------------------------------------------
> KVM VFIO device assignment cleanups for 6.17
>
> Kill off kvm_arch_{start,end}_assignment() and x86's associated tracking now
> that KVM no longer uses assigned_device_count as a bad heuristic for "VM has
> an irqbypass producer" or for "VM has access to host MMIO".
>
> ----------------------------------------------------------------
> Sean Christopherson (3):
>       Merge branch 'kvm-x86 mmio'
>       Revert "kvm: detect assigned device via irqbypass manager"
>       VFIO: KVM: x86: Drop kvm_arch_{start,end}_assignment()
>
>  arch/x86/include/asm/kvm_host.h |  2 --
>  arch/x86/kvm/irq.c              |  9 +--------
>  arch/x86/kvm/x86.c              | 18 ------------------
>  include/linux/kvm_host.h        | 18 ------------------
>  virt/kvm/vfio.c                 |  3 ---
>  5 files changed, 1 insertion(+), 49 deletions(-)
>