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Peter Anvin" , Thomas Gleixner , Makarand Sonare , Sean Christopherson References: <78cc2dc7-a2ee-35ac-dd47-8f3f8b62f261@redhat.com> <20210311200755.GE5829@zn.tnic> <20210311203206.GF5829@zn.tnic> <2ca37e61-08db-3e47-f2b9-8a7de60757e6@amd.com> <20210311214013.GH5829@zn.tnic> <4a72f780-3797-229e-a938-6dc5b14bec8d@amd.com> <20210311235215.GI5829@zn.tnic> <20210324212139.GN5010@zn.tnic> From: Paolo Bonzini Message-ID: Date: Wed, 24 Mar 2021 22:59:29 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210324212139.GN5010@zn.tnic> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 24/03/21 22:21, Borislav Petkov wrote: > if (kaiser_enabled) > invpcid_flush_one(X86_CR3_PCID_ASID_USER, addr); > + else > + asm volatile("invlpg (%0)" ::"r" (addr) : "memory"); > + > invpcid_flush_one(X86_CR3_PCID_ASID_KERN, addr); > } I think the kernel ASID flush can also be moved under the "if"? > and the reason why it does, IMHO, is because on AMD, kaiser_enabled is > false because AMD is not affected by Meltdown, which means, there's no > user/kernel pagetables split. > > And that also means, you have global TLB entries which means that if you > look at that __native_flush_tlb_single() function, it needs to flush > global TLB entries on CPUs with X86_FEATURE_INVPCID_SINGLE by doing an > INVLPG in the kaiser_enabled=0 case. Errgo, the above hunk. Makes sense. Paolo