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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1726456493; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=4VDOUWjrk1Z6cn8NNmyC0yp/VCOvweWW76Vz6loAdWQ=; b=GDSfYebvHEU5Kp59m2OwF0PkrELyiZNjMi4sP4kLmS9/pRbQDczTpLrcXG/AEAqv6f8yFL gp07bcUOlxMr5XX+gEnBGOZzxljwuBoj34Ok4ybWL8jhP7EaISL5TMRA/UiKFt2BSPxMgy FralYdzrwlNkAvMgVz226DsXeoqyxSo= 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 B1A6D1476; Sun, 15 Sep 2024 20:16:41 -0700 (PDT) Received: from [10.162.16.84] (a077893.blr.arm.com [10.162.16.84]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E6B5E3F64C; Sun, 15 Sep 2024 20:16:08 -0700 (PDT) Message-ID: <357931ba-d059-453b-a91d-1bed7fbe5914@arm.com> Date: Mon, 16 Sep 2024 08:46:06 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/7] mm: Use ptep_get() for accessing PTE entries To: Ryan Roberts , linux-mm@kvack.org Cc: Andrew Morton , David Hildenbrand , "Mike Rapoport (IBM)" , Arnd Bergmann , x86@kernel.org, linux-m68k@lists.linux-m68k.org, linux-fsdevel@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org References: <20240913084433.1016256-1-anshuman.khandual@arm.com> <20240913084433.1016256-4-anshuman.khandual@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 57421100011 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: xtq4xqihkef14yafwuyq8ywdznwfsp7u X-HE-Tag: 1726456573-7345 X-HE-Meta: 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 0uwIOvxE FRKoz9hBHk1SdiDdXGyEL9DmG7Ktca04er9Gmkxmz5NBsVZUxRNPQKddssiXQGQCsso53jnk9aiQYk2woTlUO5y2uv2FMNtHtQLhPsLVd9AMot0u2xt/kGc9HfNu2W329gZ5k6YRc79+ETprRxs/nix+2EQQ/XY26mejt6TZgmemGiK9yMEPkPezauq0QQ3Xn++lZlQOdkZg1FWyA8cOPO/TyDmPWq4CbmnvkTtS8IrqHrVQx3O3cijgtlCREXdMFMHX32q9DxPpd0NlNQhKG7JPVuvobb6VBHIaOTjcMCffatKqTOx3nsprCN+iAaRWhkh2RFHN6DwoIY/d6pZ16CuRAll2I7c72VIhwv6oqHjIHlf0E9kXfzeeAf2uDbBnxLcTrCfsoEiNa5c4jkOkWVAHVDHmiSpSZfehc8r41a+OcsxAAwVl9BNioEtu5Zmw8VzzF 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 9/13/24 15:57, Ryan Roberts wrote: > On 13/09/2024 09:44, Anshuman Khandual wrote: >> Convert PTE accesses via ptep_get() helper that defaults as READ_ONCE() but >> also provides the platform an opportunity to override when required. >> >> Cc: Andrew Morton >> Cc: David Hildenbrand >> Cc: Ryan Roberts >> Cc: "Mike Rapoport (IBM)" >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >> include/linux/pgtable.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >> index 2a6a3cccfc36..05e6995c1b93 100644 >> --- a/include/linux/pgtable.h >> +++ b/include/linux/pgtable.h >> @@ -1060,7 +1060,7 @@ static inline int pgd_same(pgd_t pgd_a, pgd_t pgd_b) >> */ >> #define set_pte_safe(ptep, pte) \ >> ({ \ >> - WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \ >> + WARN_ON_ONCE(pte_present(ptep_get(ptep)) && !pte_same(ptep_get(ptep), pte)); \ > > Suggest reading once into a temporary so that the pte can't change between the 2 > gets. In practice, it's not likely to be a huge problem for this instance since > its under the PTL so can only be racing with HW update of access and dirty. But > good practice IMHO: > > pte_t __old = ptep_get(ptep); \ > WARN_ON_ONCE(pte_present(__old) && !pte_same(__old, pte)); \ Sure, will change as suggested. > > Thanks, > Ryan > >> set_pte(ptep, pte); \ >> }) >> >