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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id h15sm1459370ejj.43.2021.01.15.05.56.41 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 15 Jan 2021 05:56:42 -0800 (PST) Subject: Re: [PATCH v2 3/3] KVM: x86: use static calls to reduce kvm_x86_ops overhead To: Peter Zijlstra , Jason Baron Cc: seanjc@google.com, kvm@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andrea Arcangeli References: From: Paolo Bonzini Message-ID: <8e13aa15-2f64-8e54-03b1-c4843af96bc1@redhat.com> Date: Fri, 15 Jan 2021 14:56:41 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 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: kvm@vger.kernel.org On 15/01/21 10:45, Peter Zijlstra wrote: > On Thu, Jan 14, 2021 at 10:27:56PM -0500, Jason Baron wrote: >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >> index 5060922..9d4492b 100644 >> --- a/arch/x86/include/asm/kvm_host.h >> +++ b/arch/x86/include/asm/kvm_host.h >> @@ -1350,7 +1350,7 @@ void kvm_arch_free_vm(struct kvm *kvm); >> static inline int kvm_arch_flush_remote_tlb(struct kvm *kvm) >> { >> if (kvm_x86_ops.tlb_remote_flush && >> - !kvm_x86_ops.tlb_remote_flush(kvm)) >> + !static_call(kvm_x86_tlb_remote_flush)(kvm)) >> return 0; >> else >> return -ENOTSUPP; > > Would you be able to use something like this? > > https://lkml.kernel.org/r/20201110101307.GO2651@hirez.programming.kicks-ass.net > > we could also add __static_call_return1(), if that would help. > I think I'd rather make the default callee return -ENOTSUPP directly and remove the "if" completely. So __static_call_return1() is not particularly useful here. Paolo