From: Dave Hansen <dave.hansen@intel.com>
To: Jim Mattson <jmattson@google.com>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
x86@kernel.org, Jon Kohler <jon@nutanix.com>,
Nikolay Borisov <nik.borisov@suse.com>,
"H. Peter Anvin" <hpa@zytor.com>,
Josh Poimboeuf <jpoimboe@kernel.org>,
David Kaplan <david.kaplan@amd.com>,
Sean Christopherson <seanjc@google.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
KP Singh <kpsingh@kernel.org>, Jiri Olsa <jolsa@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
David Laight <david.laight.linux@gmail.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
David Ahern <dsahern@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
Stanislav Fomichev <sdf@fomichev.me>, Hao Luo <haoluo@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Asit Mallick <asit.k.mallick@intel.com>,
Tao Zhang <tao1.zhang@intel.com>,
bpf@vger.kernel.org, netdev@vger.kernel.org,
linux-doc@vger.kernel.org, chao.gao@intel.com
Subject: Re: [PATCH v9 02/10] x86/bhi: Make clear_bhb_loop() effective on newer CPUs
Date: Thu, 9 Apr 2026 13:36:02 -0700 [thread overview]
Message-ID: <410df9f6-69ec-483f-9009-0a9b8c9162a9@intel.com> (raw)
In-Reply-To: <CALMp9eRfNsghM_RnDXOs=SJYObfPa5A1aOVDZno_zJ=XotfmRw@mail.gmail.com>
On 4/7/26 17:47, Jim Mattson wrote:
> On Tue, Apr 7, 2026 at 4:41 PM Dave Hansen <dave.hansen@intel.com> wrote:
>> On 4/7/26 16:27, Jim Mattson wrote:
>>> What is your proposed BHI_DIS_S override mechanism, then?
>> Let me make sure I get this right. The desire is to:
>>
>> 1. Have hypervisors lie to guests about the CPU they are running on (for
>> the benefit of large/diverse migration pools)
>> 2. Have guests be allowed to boot with BHI_DIS_S for performance
>> 3. Have apps in those guests that care about security to opt back in to
>> BHI_DIS_S for themselves?
> I just want guests on heterogeneous migration pools to properly
> protect themselves from native BHI when running on host kernels at
> least as far back as Linux v6.6.
>
> To that end, I would be satisfied with using the longer BHB clearing
> sequence when HYPERVISOR is true and BHI_CTRL is false.
If the guests can't get mitigation information from model/family because
the hypervisor is lying (or may lie), then it's on the hypervisor to
figure it out.
I'm not sure we want to just assume that all hypervisors are going to
lie all the time about this.
I kinda think we should just let Pawan's series move forward and then we
can debate the lying hypervisor problem once the series is settled.
next prev parent reply other threads:[~2026-04-09 20:36 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-03 0:30 [PATCH v9 00/10] VMSCAPE optimization for BHI variant Pawan Gupta
2026-04-03 0:30 ` [PATCH v9 01/10] x86/bhi: x86/vmscape: Move LFENCE out of clear_bhb_loop() Pawan Gupta
2026-04-03 15:16 ` Borislav Petkov
2026-04-03 16:45 ` Pawan Gupta
2026-04-03 17:11 ` Borislav Petkov
2026-04-03 0:31 ` [PATCH v9 02/10] x86/bhi: Make clear_bhb_loop() effective on newer CPUs Pawan Gupta
2026-04-03 18:10 ` Jim Mattson
2026-04-03 18:52 ` Pawan Gupta
2026-04-03 20:19 ` Jim Mattson
2026-04-03 21:34 ` Pawan Gupta
2026-04-03 21:59 ` Jim Mattson
2026-04-03 23:16 ` Pawan Gupta
2026-04-03 23:22 ` Jim Mattson
2026-04-03 23:33 ` Pawan Gupta
2026-04-03 23:39 ` Jim Mattson
2026-04-04 0:21 ` Pawan Gupta
2026-04-04 2:21 ` Jim Mattson
2026-04-04 3:49 ` Pawan Gupta
2026-04-06 14:23 ` Jim Mattson
2026-04-07 16:39 ` Pawan Gupta
2026-04-07 16:46 ` Jim Mattson
2026-04-07 17:11 ` Pawan Gupta
2026-04-07 18:40 ` Jim Mattson
2026-04-07 19:11 ` Pawan Gupta
2026-04-07 20:53 ` Jim Mattson
2026-04-07 22:27 ` Pawan Gupta
2026-04-07 23:27 ` Jim Mattson
2026-04-07 23:41 ` Dave Hansen
2026-04-08 0:47 ` Jim Mattson
2026-04-09 20:36 ` Dave Hansen [this message]
2026-04-09 21:06 ` Jim Mattson
2026-04-09 23:48 ` Pawan Gupta
2026-04-07 17:12 ` Jon Kohler
2026-04-07 17:52 ` Pawan Gupta
2026-04-03 0:31 ` [PATCH v9 03/10] x86/bhi: Rename clear_bhb_loop() to clear_bhb_loop_nofence() Pawan Gupta
2026-04-03 0:31 ` [PATCH v9 04/10] x86/vmscape: Rename x86_ibpb_exit_to_user to x86_predictor_flush_exit_to_user Pawan Gupta
2026-04-03 0:31 ` [PATCH v9 05/10] x86/vmscape: Move mitigation selection to a switch() Pawan Gupta
2026-04-03 0:32 ` [PATCH v9 06/10] x86/vmscape: Use write_ibpb() instead of indirect_branch_prediction_barrier() Pawan Gupta
2026-04-03 0:32 ` [PATCH v9 07/10] x86/vmscape: Use static_call() for predictor flush Pawan Gupta
2026-04-03 14:52 ` Sean Christopherson
2026-04-03 16:44 ` Pawan Gupta
2026-04-03 17:26 ` Pawan Gupta
2026-04-03 0:32 ` [PATCH v9 08/10] x86/vmscape: Deploy BHB clearing mitigation Pawan Gupta
2026-04-03 0:32 ` [PATCH v9 09/10] x86/vmscape: Resolve conflict between attack-vectors and vmscape=force Pawan Gupta
2026-04-03 0:33 ` [PATCH v9 10/10] x86/vmscape: Add cmdline vmscape=on to override attack vector controls Pawan Gupta
2026-04-04 15:20 ` [PATCH v9 00/10] VMSCAPE optimization for BHI variant David Laight
2026-04-05 7:23 ` Pawan Gupta
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