linux-kernel - Re: [PATCH 7/9] KVM: SVM: Treat exit_code as an unsigned 64-bit value through all of KVM

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Message-ID: <aRd2famvq_3frSEq@google.com>
Date: Fri, 14 Nov 2025 10:35:41 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Wei Liu <wei.liu@...nel.org>
Cc: Michael Kelley <mhklinux@...look.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, "K. Y. Srinivasan" <kys@...rosoft.com>, 
	Haiyang Zhang <haiyangz@...rosoft.com>, Dexuan Cui <decui@...rosoft.com>, 
	Nuno Das Neves <nunodasneves@...ux.microsoft.com>, 
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, 
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Jim Mattson <jmattson@...gle.com>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: Re: [PATCH 7/9] KVM: SVM: Treat exit_code as an unsigned 64-bit value
 through all of KVM

On Fri, Nov 14, 2025, Wei Liu wrote:
> On Fri, Nov 14, 2025 at 07:22:41AM -0800, Sean Christopherson wrote:
> > Ah, my PDF copy is just stale, it's indeed
> > defined as a synthetic exit.
> > 
> >   https://learn.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/nested-virtualization#synthetic-vm-exit
> > 
> > Anyways, I'm in favor of making HV_SVM_EXITCODE_ENL an ull, though part of me
> > wonders if we should do:
> > 
> >   #define HV_SVM_EXITCODE_ENL	SVM_EXIT_SW
> 
> I know this is very tempting, but these headers are supposed to mirror
> Microsoft's internal headers, so we would like to keep them
> self-contained for ease of tracking.

Ya, no argument from me.  Aha!  Even better, what I can do is have KVM assert
that HV_SVM_EXITCODE_ENL == SVM_EXIT_SW in the KVM Hyper-V code, because what I
really want to do is connect the dots for KVM folks.

> It should be fine to add the "ull" suffix here. I briefly talked to a
> hypervisor developer and they agreed.

Nice, thanks much!