linux-kernel - Re: [PATCH 0/3] Unify IBRS virtualization

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Message-ID: <Z-RaJVo1MKuI90G0@google.com>
Date: Wed, 26 Mar 2025 12:48:53 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Yosry Ahmed <yosry.ahmed@...ux.dev>
Cc: x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	"H. Peter Anvin" <hpa@...or.com>, Paolo Bonzini <pbonzini@...hat.com>, Jim Mattson <jmattson@...gle.com>, 
	David Kaplan <David.Kaplan@....com>, kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] Unify IBRS virtualization

On Thu, Mar 13, 2025, Yosry Ahmed wrote:
> On Fri, Feb 21, 2025 at 04:33:49PM +0000, Yosry Ahmed wrote:
> > To properly virtualize IBRS on Intel, an IBPB is executed on emulated
> > VM-exits to provide separate predictor modes for L1 and L2.
> > 
> > Similar handling is theoretically needed for AMD, unless IbrsSameMode is
> > enumerated by the CPU (which should be the case for most/all CPUs
> > anyway). For correctness and clarity, this series generalizes the
> > handling to apply for both Intel and AMD as needed.
> > 
> > I am not sure if this series would land through the kvm-x86 tree or the
> > tip/x86 tree.
> 
> Sean, any thoughts about this (or general feedback about this series)?

No feedback, I just you and Jim to get mitigation stuff right far more than I
trust myself :-)

I'm planning on grabbing this for 6.16.