linux-kernel - Re: [PATCH v15 01/41] KVM: SEV: Rename kvm_ghcb_get_sw_exit_code() to kvm_get_cached_sw_exit

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Message-ID: <aMg_KownKheaKeCZ@google.com>
Date: Mon, 15 Sep 2025 09:30:34 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Mathias Krause <minipli@...ecurity.net>, John Allen <john.allen@....com>, 
	Rick Edgecombe <rick.p.edgecombe@...el.com>, Chao Gao <chao.gao@...el.com>, 
	Maxim Levitsky <mlevitsk@...hat.com>, Xiaoyao Li <xiaoyao.li@...el.com>, 
	Zhang Yi Z <yi.z.zhang@...ux.intel.com>
Subject: Re: [PATCH v15 01/41] KVM: SEV: Rename kvm_ghcb_get_sw_exit_code() to kvm_get_cached_sw_exit_code()

On Mon, Sep 15, 2025, Tom Lendacky wrote:
> On 9/12/25 18:22, Sean Christopherson wrote:
> > Rename kvm_ghcb_get_sw_exit_code() to kvm_get_cached_sw_exit_code() to make
> > it clear that KVM is getting the cached value, not reading directly from
> > the guest-controlled GHCB.  More importantly, vacating
> > kvm_ghcb_get_sw_exit_code() will allow adding a KVM-specific macro-built
> > kvm_ghcb_get_##field() helper to read values from the GHCB.
> > 
> > No functional change intended.
> > 
> > Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> 
> Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> 
> Makes me wonder if we want to create kvm_get_cached_sw_exit_info_{1,2}
> routines rather than referencing control->exit_info_{1,2} directly?

I think I'd prefer to avoid creating more wrappers?  I generally don't like having
wrappers for accessing a single field, especially an architecturally defined field,
because I don't like having to bounce through extra layers to understand what's
going on.

But for the GHCB wrappers, they're a necessary evil due to the associated valid
bits and the volatility (guest-writable) of the fields.  For the "cached" fields,
I don't think we need a wrappers; providing a helper to splice the two exit code
fields together is helpful, but accessing the control area directly for "simple"
cases feels very natural to me since that's how KVM works for "normal" VMs.