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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id h7sm218074edt.37.2021.10.27.08.37.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Oct 2021 08:37:56 -0700 (PDT) Message-ID: <5b8f554b-5bbc-e257-12d0-800ec82489d0@redhat.com> Date: Wed, 27 Oct 2021 17:37:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH v2 00/43] KVM: Halt-polling and x86 APICv overhaul Content-Language: en-US To: Sean Christopherson Cc: Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , James Morse , Alexandru Elisei , Suzuki K Poulose , Atish Patra , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , Oliver Upton , Jing Zhang References: <20211009021236.4122790-1-seanjc@google.com> <614858dd-106c-64cc-04bc-f1887b2054d1@redhat.com> From: Paolo Bonzini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/10/21 17:28, Sean Christopherson wrote: > On Wed, Oct 27, 2021, Paolo Bonzini wrote: >> On 27/10/21 16:41, Sean Christopherson wrote: >>> The other thing I don't like about having the WARN in the loop is that it suggests >>> that something other than the vCPU can modify the NDST and SN fields, which is >>> wrong and confusing (for me). >> >> Yeah, I can agree with that. Can you add it in a comment above the cmpxchg >> loop, it can be as simple as >> >> /* The processor can set ON concurrently. */ >> >> when you respin patch 21 and the rest of the series? > > I can definitely add a comment, but I think that comment is incorrect. It's completely backwards indeed. I first had "the hardware" and then shut down my brain for a second to replace it. > So something like this? > > /* ON can be set concurrently by a different vCPU or by hardware. */ Yes, of course. Paolo