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imf08.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf08.hostedemail.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706758240; a=rsa-sha256; cv=none; b=FCOXNLScxSFNwS9LPJ84wcjxr9aERKx5bAri0GF5At6PPHrRzYMpHMO4bJO5lbpvghDwgJ C06B5/EOGTjRDPXq49Lj/U9JtbUZCo5krjVfMKDu1P++Mx2UMpQkydK0yGQNceSshmBQMd Y1JkTrYVrem1o/vl0E9rPmCHtZHa5jQ= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A4B63DA7; Wed, 31 Jan 2024 19:31:21 -0800 (PST) Received: from [10.162.42.11] (a077893.blr.arm.com [10.162.42.11]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DADF33F738; Wed, 31 Jan 2024 19:30:26 -0800 (PST) Message-ID: <08a4971e-c31d-46f7-afbc-7404bd9a293f@arm.com> Date: Thu, 1 Feb 2024 09:00:23 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3 12/35] mm: Call arch_swap_prepare_to_restore() before arch_swap_restore() Content-Language: en-US To: Alexandru Elisei , catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org, rppt@kernel.org, hughd@google.com Cc: pcc@google.com, steven.price@arm.com, vincenzo.frascino@arm.com, david@redhat.com, eugenis@google.com, kcc@google.com, hyesoo.yu@samsung.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org References: <20240125164256.4147-1-alexandru.elisei@arm.com> <20240125164256.4147-13-alexandru.elisei@arm.com> From: Anshuman Khandual In-Reply-To: <20240125164256.4147-13-alexandru.elisei@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: BF45716000C X-Stat-Signature: cbbm1ihit9asge5ga4xxyc7jy8barthq X-Rspam-User: X-HE-Tag: 1706758239-30491 X-HE-Meta: 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 CJ8hhtp2 xJqNr9aEQp+YoFw0m0ElIfyz4ZZtesvHFOZC7PKQMzTlM1Xx8djrCyuUVul5FwdLlkFh3yDRcr7a3KG6dmj9VoWYCd3o/XCFWzcVY4LGbS9ePjXRzOQlDmQ85RHRVwNCHOUWUnTYDvPI0KEFgNYHSYHlmpBVkA4mnsM2QpaMBHKv2EOFzdtZYKP9mHz4PPbS6GXFX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 1/25/24 22:12, Alexandru Elisei wrote: > arm64 uses arch_swap_restore() to restore saved tags before the page is > swapped in and it's called in atomic context (with the ptl lock held). > > Introduce arch_swap_prepare_to_restore() that will allow an architecture to > perform extra work during swap in and outside of a critical section. > This will be used by arm64 to allocate a buffer in memory where to > temporarily save tags if tag storage is not available for the page being > swapped in. Just wondering if tag storage will always be unavailable for tagged pages being swapped in ? OR there are cases where allocation might not even be required ? This prepare phase needs to be outside the critical section - only because there might be memory allocations ?