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Tue, 11 May 2021 14:07:18 +0000 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 9FB2E101E; Tue, 11 May 2021 07:07:13 -0700 (PDT) Received: from C02TD0UTHF1T.local (unknown [10.57.29.91]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1BB9C3F718; Tue, 11 May 2021 07:07:10 -0700 (PDT) Date: Tue, 11 May 2021 15:07:08 +0100 From: Mark Rutland To: Anshuman Khandual Cc: linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , linux-kernel@vger.kernel.org Subject: Re: [PATCH] arm64/mm: Remove [PUD|PMD]_TABLE_BIT from [pud|pmd]_bad() Message-ID: <20210511140708.GC8933@C02TD0UTHF1T.local> References: <1620644871-26280-1-git-send-email-anshuman.khandual@arm.com> <20210510144337.GA92897@C02TD0UTHF1T.local> <4a36d7b7-6b27-31cc-d701-ebe3c6e4946e@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4a36d7b7-6b27-31cc-d701-ebe3c6e4946e@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210511_070716_952637_1C0DF996 X-CRM114-Status: GOOD ( 23.58 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, May 11, 2021 at 09:21:46AM +0530, Anshuman Khandual wrote: > > On 5/10/21 8:13 PM, Mark Rutland wrote: > > On Mon, May 10, 2021 at 04:37:51PM +0530, Anshuman Khandual wrote: > >> Semantics wise, [pud|pmd]_bad() have always implied that a given [PUD|PMD] > >> entry does not have a pointer to the next level page table. This had been > >> made clear in the commit a1c76574f345 ("arm64: mm: use *_sect to check for > >> section maps"). Hence explicitly check for a table entry rather than just > >> testing a single bit. This basically redefines [pud|pmd]_bad() in terms of > >> [pud|pmd]_table() making the semantics clear. > >> > >> Cc: Catalin Marinas > >> Cc: Will Deacon > >> Cc: Mark Rutland > >> Cc: linux-arm-kernel@lists.infradead.org > >> Cc: linux-kernel@vger.kernel.org > >> Signed-off-by: Anshuman Khandual > > > > I have no strong feelings either way, so: > > > > Acked-by: Mark Rutland > > > > ... that said, I think that the "bad" naming is unclear and misleading, > > and it'd be really nice if we could clean that up treewide with > > something clearer than "bad". > > Agreed, the name is misleading. > > > It does seem that would roughly fit p??_leaf() if we had > > But what if the platform does not support huge page aka leaf mapping > at the given level ? Also a non table i.e bad entry might not always > mean a leaf/section/huge page mapping, it could simply imply that the > entry is not just pointing to next level and might be just in an bad > intermediate or invalid state. Ah, so that's also covering swap entries, too? It's not entirely clear to me what "bad intermediate or invalid state" means, because I assume it's not arbitrary junk or this wouldn't be sound genrally. I had assumed it was only covering *valid* non-table entries. > > p??_clear_leaf() and p??_none_or_clear_leaf() helpers. > > Could you please elaborate how these new helpers might help define > pxx_bad() ? This was based on my (evidently wrong) prior understanding above. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel