From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BD4E324B41 for ; Mon, 4 Dec 2023 13:09:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from kwepemm000007.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4SkP5759swz14L9q; Mon, 4 Dec 2023 21:04:27 +0800 (CST) Received: from [10.174.185.179] (10.174.185.179) by kwepemm000007.china.huawei.com (7.193.23.189) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.35; Mon, 4 Dec 2023 21:09:23 +0800 Subject: Re: [PATCH v2 0/3] arm64: Drop support for VPIPT i-cache policy To: Marc Zyngier CC: , , , Will Deacon , Catalin Marinas , Mark Rutland , Ard Biesheuvel , James Morse , Suzuki K Poulose , Oliver Upton References: <20231127172613.1490283-1-maz@kernel.org> From: Zenghui Yu Message-ID: <6f859b31-dcbe-148d-cfde-e6119553b072@huawei.com> Date: Mon, 4 Dec 2023 21:09:22 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20231127172613.1490283-1-maz@kernel.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemm000007.china.huawei.com (7.193.23.189) X-CFilter-Loop: Reflected On 2023/11/28 1:26, Marc Zyngier wrote: > ARMv8.2 introduced support for VPIPT i-caches, the V standing for > VMID-tagged. Although this looks like a reasonable idea, no > implementation has ever made it into the wild. > > Linux has supported this for over 6 years (amusingly, just as the > architecture was dropping support for AVIVT i-caches), but we had no > way to even test it, and it is likely that this code was just > bit-rotting. > > However, in a recent breakthrough (XML drop 2023-09, tagged as > d55f5af8e09052abe92a02adf820deea2eaed717), the architecture has > finally been purged of this option, making VIPT and PIPT the only two > valid options. > > This really means this code is just dead code. Nobody will ever come > up with such an implementation, and we can just get rid of it. > > Most of the impact is on KVM, where we drop a few large comment blocks > (and a bit of code), while the core arch code loses the detection code > itself. > > Marc Zyngier (3): > KVM: arm64: Remove VPIPT I-cache handling > arm64: Kill detection of VPIPT i-cache policy > arm64: Rename reserved values for CTR_EL0.L1Ip Series looks good to me. With Anshuman's comment addressed, Reviewed-by: Zenghui Yu