linux-kernel - Re: [PATCH v4 07/11] x86/vmscape: Use write_ibpb() instead of indirect_branch_prediction

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Message-ID: <ebf8f16d-3d48-474b-a620-98456d31b4cc@suse.com>
Date: Fri, 21 Nov 2025 14:59:35 +0200
From: Nikolay Borisov <nik.borisov@...e.com>
To: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, x86@...nel.org,
 David Kaplan <david.kaplan@....com>, "H. Peter Anvin" <hpa@...or.com>,
 Josh Poimboeuf <jpoimboe@...nel.org>, Sean Christopherson
 <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
 Asit Mallick <asit.k.mallick@...el.com>, Tao Zhang <tao1.zhang@...el.com>
Subject: Re: [PATCH v4 07/11] x86/vmscape: Use write_ibpb() instead of
 indirect_branch_prediction_barrier()

On 11/20/25 08:19, Pawan Gupta wrote:
> indirect_branch_prediction_barrier() is a wrapper to write_ibpb(), which
> also checks if the CPU supports IBPB. For VMSCAPE, call to
> indirect_branch_prediction_barrier() is only possible when CPU supports
> IBPB.
> 
> Simply call write_ibpb() directly to avoid unnecessary alternative
> patching.
> 
> Suggested-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>

Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>