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Tue, 08 Apr 2025 06:50:45 -0700 (PDT) Received: from [192.168.0.20] ([212.21.133.214]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac7bfe99c7dsm925314966b.57.2025.04.08.06.50.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Apr 2025 06:50:44 -0700 (PDT) Message-ID: Date: Tue, 8 Apr 2025 16:50:42 +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 4/6] x86/bugs: Don't fill RSB on VMEXIT with eIBRS+retpoline 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: From: Nikolay Borisov Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 2.04.25 г. 21:19 ч., Josh Poimboeuf wrote: > eIBRS protects against guest->host RSB underflow/poisoning attacks. > Adding retpoline to the mix doesn't change that. Retpoline has a > balanced CALL/RET anyway. > > So the current full RSB filling on VMEXIT with eIBRS+retpoline is > overkill. Disable it or do the VMEXIT_LITE mitigation if needed. > > Suggested-by: Pawan Gupta > Reviewed-by: Pawan Gupta > Reviewed-by: Amit Shah > Signed-off-by: Josh Poimboeuf Reviewed-by: Nikolay Borisov