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Tue, 08 Apr 2025 06:51:46 -0700 (PDT) Received: from [192.168.0.20] ([212.21.133.214]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac7c013f363sm924386266b.105.2025.04.08.06.51.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Apr 2025 06:51:46 -0700 (PDT) Message-ID: <80e2557d-b4b0-4097-9662-8772d2af25fe@suse.com> Date: Tue, 8 Apr 2025 16:51:43 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 5/6] x86/bugs: Don't fill RSB on context switch with eIBRS To: Josh Poimboeuf , x86@kernel.org Cc: linux-kernel@vger.kernel.org, amit@kernel.org, kvm@vger.kernel.org, amit.shah@amd.com, thomas.lendacky@amd.com, bp@alien8.de, tglx@linutronix.de, peterz@infradead.org, pawan.kumar.gupta@linux.intel.com, corbet@lwn.net, mingo@redhat.com, dave.hansen@linux.intel.com, hpa@zytor.com, seanjc@google.com, pbonzini@redhat.com, daniel.sneddon@linux.intel.com, kai.huang@intel.com, sandipan.das@amd.com, boris.ostrovsky@oracle.com, Babu.Moger@amd.com, david.kaplan@amd.com, dwmw@amazon.co.uk, andrew.cooper3@citrix.com References: <8979e2e1d9f48aa4480c2ebd5ea0f9e31f9707e5.1743617897.git.jpoimboe@kernel.org> From: Nikolay Borisov Content-Language: en-US In-Reply-To: <8979e2e1d9f48aa4480c2ebd5ea0f9e31f9707e5.1743617897.git.jpoimboe@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2.04.25 г. 21:19 ч., Josh Poimboeuf wrote: > User->user Spectre v2 attacks (including RSB) across context switches > are already mitigated by IBPB in cond_mitigation(), if enabled globally > or if either the prev or the next task has opted in to protection. RSB > filling without IBPB serves no purpose for protecting user space, as > indirect branches are still vulnerable. > > User->kernel RSB attacks are mitigated by eIBRS. In which case the RSB > filling on context switch isn't needed, so remove it. > > Suggested-by: Pawan Gupta > Reviewed-by: Pawan Gupta > Reviewed-by: Amit Shah > Signed-off-by: Josh Poimboeuf Reviewed-by: Nikolay Borisov