linux-kernel - Re: [PATCH v13 05/21] KVM: pfncache: remove KVM_GUEST_USES

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Message-ID: <ZdPLmEeMhTaSiYrA@google.com>
Date: Mon, 19 Feb 2024 13:43:52 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Paul Durrant <paul@....org>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Jonathan Corbet <corbet@....net>, 
	Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, 
	Claudio Imbrenda <imbrenda@...ux.ibm.com>, David Hildenbrand <david@...hat.com>, 
	Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>, 
	Alexander Gordeev <agordeev@...ux.ibm.com>, Sven Schnelle <svens@...ux.ibm.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>, David Woodhouse <dwmw2@...radead.org>, Shuah Khan <shuah@...nel.org>, 
	kvm@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-s390@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v13 05/21] KVM: pfncache: remove KVM_GUEST_USES_PFN usage

On Thu, Feb 15, 2024, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@...zon.com>
> 
> As noted in [1] the KVM_GUEST_USES_PFN usage flag is never set by any
> callers of kvm_gpc_init(), which also makes the 'vcpu' argument redundant.

The changelog should explicitly call out that not only is KVM_GUEST_USES_PFN
unused, it's incomplete/broken (which is also partly why it's unused).  Without
that information, removing the support looks like a somewhat arbitrary decision,
versus a deliberate change to make it easier to support the gpc code.