linux-kernel - Re: [PATCH 1/3] kvm: vmx: Add IA32_FLUSH

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Date:   Tue, 21 Mar 2023 16:59:08 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        kvm@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        Ben Serebrin <serebrin@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] kvm: vmx: Add IA32_FLUSH_CMD guest support

On Mon, Mar 20, 2023, Sean Christopherson wrote:
> On Fri, Mar 17, 2023, Pawan Gupta wrote:
> > Thats what I think, and if its too late to be squashed I will send a
> > formal patch. Maintainers?
> 
> Honestly, I'd rather revert the whole mess and try again.  The patches obviously
> weren't tested, and the entire approach (that was borrowed from the existing
> MSR_IA32_PRED_CMD code) makes no sense.

Yeah, revert incoming.  This is just the tip of the iceberg.  SVM completely drops
the error,  which is why there are no boot failures on AMD despite having the same
broken logic.  Neither SVM nor VMX marks the MSR as being passthrough friendly and
thus breaks MSR filtering.