linux-kernel - Re: [PATCH] KVM: VMX: Add a wrapper for reading INVPCID/INVEPT/INVVPID type

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Message-ID: <YYGPPgCUWSEt0rQ0@google.com>
Date:   Tue, 2 Nov 2021 19:19:26 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Vipin Sharma <vipinsh@...gle.com>
Cc:     Jim Mattson <jmattson@...gle.com>, pbonzini@...hat.com,
        dmatlack@...gle.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: VMX: Add a wrapper for reading
 INVPCID/INVEPT/INVVPID type

On Tue, Nov 02, 2021, Vipin Sharma wrote:
> Sorry for the late reply.
> 
> On Thu, Oct 14, 2021 at 10:05 AM Jim Mattson <jmattson@...gle.com> wrote:
> >
> > On Thu, Oct 14, 2021 at 9:54 AM Sean Christopherson <seanjc@...gle.com> wrote:
> > > Oh, yeah, definitely.  I missed that SVM's invpcid_interception() has the same
> > > open-coded check.
> > >
> > > Alternatively, could we handle the invalid type in the main switch statement?  I
> > > don't see anything in the SDM or APM that architecturally _requires_ the type be
> > > checked before reading the INVPCID descriptor.  Hardware may operate that way,
> > > but that's uArch specific behavior unless there's explicit documentation.
> >
> > Right. INVVPID and INVEPT are explicitly documented to check the type
> > first, but INVPCID is not.
> 
> It seems to me that I can move type > 3 check to kvm_handle_invpcid()
> switch statement. I can replace BUG() in that switch statement with
> kvm_inject_gp for the default case, I won't even need INVPCID_TYPE_MAX
> in this case.

Yep.

> If you are fine with this approach then I will send out a patch where
> invalid type is handled  in kvm_handle_invpcid() switch statement.

This has my vote.