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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id sb20sm12114420ejb.100.2021.05.11.10.08.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 May 2021 10:08:08 -0700 (PDT) Subject: Re: [PATCH v2] KVM: x86: use wrpkru directly in kvm_load_{guest|host}_xsave_state To: Dave Hansen , Jon Kohler Cc: Babu Moger , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Yu-cheng Yu , Fenghua Yu , Tony Luck , Petteri Aimonen , Kan Liang , Uros Bizjak , Andrew Morton , Mike Rapoport , Benjamin Thiel , Anshuman Khandual , Juergen Gross , Fan Yang , Dave Jiang , "Peter Zijlstra (Intel)" , Ricardo Neri , Arvind Sankar , linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20210511155922.36693-1-jon@nutanix.com> From: Paolo Bonzini Message-ID: <95947b5c-9add-e5d3-16a5-a40ab6d24978@redhat.com> Date: Tue, 11 May 2021 19:08:06 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: 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 11/05/21 18:45, Dave Hansen wrote: > On 5/11/21 8:59 AM, Jon Kohler wrote: >> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >> index b1099f2d9800..20f1fb8be7ef 100644 >> --- a/arch/x86/include/asm/pgtable.h >> +++ b/arch/x86/include/asm/pgtable.h >> @@ -151,7 +151,7 @@ static inline void write_pkru(u32 pkru) >> fpregs_lock(); >> if (pk) >> pk->pkru = pkru; >> - __write_pkru(pkru); >> + wrpkru(pkru); >> fpregs_unlock(); >> } > > This removes the: > > if (pkru == rdpkru()) > return; > > optimization from a couple of write_pkru() users: > arch_set_user_pkey_access() and copy_init_pkru_to_fpregs(). > > Was that intentional? Those aren't the hottest paths in the kernel, but > copy_init_pkru_to_fpregs() is used in signal handling and exeve(). Yeah, you should move it from __write_pkru() to write_pkru() but not remove it completely. Paolo