From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: Nikolay Borisov <nik.borisov@suse.com>
Cc: x86@kernel.org, David Kaplan <david.kaplan@amd.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Josh Poimboeuf <jpoimboe@kernel.org>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Asit Mallick <asit.k.mallick@intel.com>,
Tao Zhang <tao1.zhang@intel.com>
Subject: Re: [PATCH v4 06/11] x86/vmscape: Move mitigation selection to a switch()
Date: Tue, 25 Nov 2025 09:45:41 -0800 [thread overview]
Message-ID: <20251125174541.7lgjdfwws4ios4vg@desk> (raw)
In-Reply-To: <c1b67fb1-0ef9-4f23-9e09-c5eecc18f595@suse.com>
On Tue, Nov 25, 2025 at 12:19:32PM +0200, Nikolay Borisov wrote:
> > FEATURE_IBPB check is still needed for VMSCAPE_MITIGATION_IBPB_EXIT_TO_USER.
> > I don't think we can drop that.
>
> But if X86_FEATURE_IBPB is not present then all branches boil down to
> setting the mitigation to NONE. What I was suggesting is to not remove the
> that check at the top.
BHB_CLEAR mitigation is still possible without IBPB, with that IBPB check cannot
be at the top. This patch prepares for adding BHB_CLEAR support.
Sure I can delay moving the IBPB check to later patch, but the intent of
splitting the patches was to keep the patch that move the existing logic
separate from the one that adds a new mitigation.
next prev parent reply other threads:[~2025-11-25 17:45 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-20 6:17 [PATCH v4 00/11] VMSCAPE optimization for BHI variant Pawan Gupta
2025-11-20 6:17 ` [PATCH v4 01/11] x86/bhi: x86/vmscape: Move LFENCE out of clear_bhb_loop() Pawan Gupta
2025-11-20 16:15 ` Nikolay Borisov
2025-11-20 16:56 ` Pawan Gupta
2025-11-20 16:58 ` Nikolay Borisov
2025-11-20 6:18 ` [PATCH v4 02/11] x86/bhi: Move the BHB sequence to a macro for reuse Pawan Gupta
2025-11-20 16:28 ` Nikolay Borisov
2025-11-20 16:57 ` Pawan Gupta
2025-11-25 0:21 ` Pawan Gupta
2025-11-20 6:18 ` [PATCH v4 03/11] x86/bhi: Make the depth of BHB-clearing configurable Pawan Gupta
2025-11-20 17:02 ` Nikolay Borisov
2025-11-20 6:18 ` [PATCH v4 04/11] x86/bhi: Make clear_bhb_loop() effective on newer CPUs Pawan Gupta
2025-11-21 12:33 ` Nikolay Borisov
2025-11-21 16:40 ` Dave Hansen
2025-11-21 16:45 ` Nikolay Borisov
2025-11-21 16:50 ` Dave Hansen
2025-11-21 18:16 ` Pawan Gupta
2025-11-21 18:42 ` Dave Hansen
2025-11-21 21:26 ` Pawan Gupta
2025-11-21 21:36 ` Dave Hansen
2025-11-24 19:21 ` Pawan Gupta
2025-11-22 11:05 ` david laight
2025-11-24 19:31 ` Pawan Gupta
2025-11-25 11:34 ` david laight
2025-12-04 1:40 ` Pawan Gupta
2025-12-04 9:15 ` david laight
2025-12-04 21:56 ` Pawan Gupta
2025-12-05 9:21 ` david laight
2025-11-26 19:23 ` Pawan Gupta
2026-03-06 21:00 ` Jim Mattson
2026-03-06 22:32 ` Pawan Gupta
2026-03-06 22:57 ` Jim Mattson
2026-03-06 23:29 ` Pawan Gupta
2026-03-07 0:35 ` Jim Mattson
2026-03-07 1:00 ` Pawan Gupta
2026-03-07 1:10 ` Jim Mattson
2026-03-07 2:41 ` Pawan Gupta
2026-03-07 5:05 ` Jim Mattson
2026-03-09 22:29 ` Pawan Gupta
2026-03-09 23:05 ` Jim Mattson
2026-03-10 0:00 ` Pawan Gupta
2026-03-10 0:08 ` Jim Mattson
2026-03-10 0:52 ` Pawan Gupta
2025-11-20 6:18 ` [PATCH v4 05/11] x86/vmscape: Rename x86_ibpb_exit_to_user to x86_predictor_flush_exit_to_user Pawan Gupta
2025-11-20 6:19 ` [PATCH v4 06/11] x86/vmscape: Move mitigation selection to a switch() Pawan Gupta
2025-11-21 14:27 ` Nikolay Borisov
2025-11-24 23:09 ` Pawan Gupta
2025-11-25 10:19 ` Nikolay Borisov
2025-11-25 17:45 ` Pawan Gupta [this message]
2025-11-20 6:19 ` [PATCH v4 07/11] x86/vmscape: Use write_ibpb() instead of indirect_branch_prediction_barrier() Pawan Gupta
2025-11-21 12:59 ` Nikolay Borisov
2025-11-20 6:19 ` [PATCH v4 08/11] x86/vmscape: Use static_call() for predictor flush Pawan Gupta
2025-11-20 6:19 ` [PATCH v4 09/11] x86/vmscape: Deploy BHB clearing mitigation Pawan Gupta
2025-11-21 14:18 ` Nikolay Borisov
2025-11-21 18:29 ` Pawan Gupta
2025-11-21 14:23 ` Nikolay Borisov
2025-11-21 18:41 ` Pawan Gupta
2025-11-21 18:53 ` Nikolay Borisov
2025-11-21 21:29 ` Pawan Gupta
2025-11-20 6:20 ` [PATCH v4 10/11] x86/vmscape: Override conflicting attack-vector controls with =force Pawan Gupta
2025-11-21 18:04 ` Nikolay Borisov
2025-11-20 6:20 ` [PATCH v4 11/11] x86/vmscape: Add cmdline vmscape=on to override attack vector controls Pawan Gupta
2025-11-25 11:41 ` Nikolay Borisov
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