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[92.178.7.112]) by smtp.gmail.com with UTF8SMTPSA id ffacd0b85a97d-3b4708d094csm2994854f8f.28.2025.07.04.10.53.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Jul 2025 10:53:46 -0700 (PDT) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: d56f6206-58ff-11f0-b894-0df219b8e170 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=citrix.com; s=google; t=1751651626; x=1752256426; darn=lists.xenproject.org; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=3SKvZjYMUoxFeGJh3oZxTgufBc5EyFMOxJZOyOwY81s=; b=UbhkiWjvFHuAePhbhKs8uahIetm7xTEsRGjCy0NwZnWmq7EZESWtGRryNrmE+jhP// ykGKYkC97N74j/6b2YtXzMy2tNsefeGz3svX8z3qyAE/yuayuBGZyC+BqgXmvTI0fCNd WgF9nEdbZPeDKyXROv8L+9LixoPMqrEB9it7k= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1751651626; x=1752256426; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=3SKvZjYMUoxFeGJh3oZxTgufBc5EyFMOxJZOyOwY81s=; b=YzokjnQuW9bdqYyx6cQzZ5da4oqv/SdKJMV+y+Ucr5fHWpizOWCwHT5hLOA+QYIV5a lP7KTaJJG72uuaRlExzqr2bxLoXho4sFDcIRbNQW6vrIRvo+oLSEbF01keJoYgpD67di qvW0c/MonLAUgVpXiVelsdMIlZqEh+UNpVsoWRuKK8ZXwYZR3rr8T4/i0oaSbkhlIMx2 sRR9cNI089ViCa4bI0onxX/b8JLKSRLlLIQKfyyoq1bACiLtyykfNKvyTA8IZiVWTuGD p+X8WuxC5hMjx6CFm98MkjEGEHWlgJv+8Sh5ZXB2ryI+a0sbCZLL0yNifsq0wj/ZgIQ0 8ivQ== X-Gm-Message-State: AOJu0Yzr4Z7Vl+k+PRPDFPUuJngheGwRSM4bGfZDOUHuymF60uFPkngL rcAAfo8dpLF8FjmWisbCF8gNTeWM24K9CKUbbggyDuKgaf4aXy7fO1/eIhf3KvoGKrg= X-Gm-Gg: ASbGncvH1D2JglcfTLg4SJjU9Ysk0DxiDAcCFF2aUkXiDEP/Y70G24ID//Zx5KuXtoJ OyLWWc7qpHV9D2wNXlNHMlKfmmjFiB7poGz03vojLiSFrGwTHfr8M8Ujz5Aa2q5o5GsRjkOfTOO 8KK3c3tJdJdkJB2QoYhd7hdI0dM1JH1lLPH9VvO4DqYAvIQbeDgckpmWE15pj6RI/8RLNxLoiTR Fnu9BJztyZwjWc8TkLIg8M4+2qS7EZod1AuzqmsA3Fmw3kZByBGiMw8AdfgzWpmtVTnI7XVo7JR Wmey8S7UGJznRe2T3buxRJN5mqWKwAiQs+J4StOQgQQDQGUJJUg/pYhxuO8tqdt6wn256BSN+Me 86X2jxnPwZSthohOfb3ydJjEEZzkUlA== X-Google-Smtp-Source: AGHT+IEAonGI7gp9ijdBJLZYzRUyoWeZfw+cpFxoZdYROHxw3aMTrdoL+eNXLuJPAIwMEgUqfpqf6Q== X-Received: by 2002:a05:6000:2285:b0:3aa:c95b:d1d9 with SMTP id ffacd0b85a97d-3b4964eb200mr2641330f8f.6.1751651626460; Fri, 04 Jul 2025 10:53:46 -0700 (PDT) Date: Fri, 4 Jul 2025 19:53:45 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Andrew Cooper Cc: Xen-devel , Jan Beulich , Anthony PERARD , Michal Orzel , Julien Grall , Stefano Stabellini Subject: Re: [PATCH v2 5/6] x86/idle: Implement a new MWAIT IPI-elision algorithm Message-ID: References: <20250704163410.1412367-1-andrew.cooper3@citrix.com> <20250704163410.1412367-6-andrew.cooper3@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250704163410.1412367-6-andrew.cooper3@citrix.com> On Fri, Jul 04, 2025 at 05:34:09PM +0100, Andrew Cooper wrote: > In order elide IPIs, we must be able to identify whether a target CPU is in > MWAIT at the point it is woken up. i.e. the store to wake it up must also > identify the state. > > Create a new in_mwait variable beside __softirq_pending, so we can use a > CMPXCHG to set the softirq while also observing the status safely. Implement > an x86 version of arch_pend_softirq() which does this. > > In mwait_idle_with_hints(), advertise in_mwait, with an explanation of > precisely what it means. X86_BUG_MONITOR can be accounted for simply by not > advertising in_mwait. > > Signed-off-by: Andrew Cooper Acked-by: Roger Pau Monné Thanks, Roger.