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Wed, 21 Aug 2024 02:38:36 -0700 (PDT) MIME-Version: 1.0 References: <20240712-asi-rfc-24-v1-0-144b319a40d8@google.com> <20240712-asi-rfc-24-v1-26-144b319a40d8@google.com> <49849e0b-5ed6-44a4-94b3-1d5dd54b9a29@amd.com> In-Reply-To: <49849e0b-5ed6-44a4-94b3-1d5dd54b9a29@amd.com> From: Brendan Jackman Date: Wed, 21 Aug 2024 11:38:21 +0200 Message-ID: Subject: Re: [PATCH 26/26] KVM: x86: asi: Add some mitigations on address space transitions To: Shivank Garg Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , Andy Lutomirski , Peter Zijlstra , Sean Christopherson , Paolo Bonzini , Alexandre Chartre , Liran Alon , Jan Setje-Eilers , Catalin Marinas , Will Deacon , Mark Rutland , Andrew Morton , Mel Gorman , Lorenzo Stoakes , David Hildenbrand , Vlastimil Babka , Michal Hocko , Khalid Aziz , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Valentin Schneider , Paul Turner , Reiji Watanabe , Junaid Shahid , Ofir Weisse , Yosry Ahmed , Patrick Bellasi , KP Singh , Alexandra Sandulescu , Matteo Rizzo , Jann Horn , x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 92F6016000F X-Stat-Signature: teczzaxuey15bmipw3mw11ggn8zc9a4d X-HE-Tag: 1724233117-573948 X-HE-Meta: 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 4yl+xjrD PU9jEh7q32qK0yCRTDdp4fbCTUdGb1ddFVnKgxoA/rg1YIbjR/CKEkm+CikWKN+X7TW4/hqPazZqi5yfbhGOm/2ER4WLTfuOcCTA1XBr8teX1U4q1IHbqCf9A7c3UibRKMRMk5N1qOJdNPdT1ykkBo3hd4Wr3MxQTIBwPaPxzSDGv51XKD8tGdQJds/DyIT+gRJl+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Shivank, On Tue, 20 Aug 2024 at 11:52, Shivank Garg wrote: > > .pushsection .noinstr.text, "ax" > SYM_CODE_START(fill_return_buffer) > + UNWIND_HINT_FUNC > __FILL_RETURN_BUFFER(%_ASM_AX,RSB_CLEAR_LOOPS) > RET > SYM_CODE_END(fill_return_buffer) > +__EXPORT_THUNK(fill_return_buffer) > .popsection Thanks a lot for the pointer! UNWIND_HINT_FUNC does indeed seem to be what I was missing with the objtool warning. Regarding the build failure, could you share your config/toolchain info so I can try to reproduce? Would be handy for checking my next posting. Now I see your mail, it seems surprising that it compiles for me. Also while I'm replying to this thread I'll note this: > + if (!IS_ENABLED(CONFIG_RETPOLINE) || > + !cpu_feature_enabled(X86_FEATURE_RSB_VMEXIT)) It's called CONFIG_MITIGATION_RETPOLINE now. And furthermore, kvm_get_running_vcpu needs to be noinstr, I'm getting an objtool warning about this that wasn't mentioned in my cover letter.