From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta0.migadu.com (out-238.mta0.migadu.com [91.218.175.238]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CF0C035F170 for ; Tue, 22 Sep 2026 12:52:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.238 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790081576; cv=none; b=u6RdrYysLRvmQnG/ieFlya6m+e8qru0jbEUDuI2k3LXjzptC1QaXZPAYXwqK3XFu75eKFo+R6MN2b9GbbRHRdUaxN+j2s7S797tVamCs4FpmfxsHpl+rQ5mBWKJkhoOUc4O06a7G3M3Dsw/nA6mnjDLG8josxyttyXEPBcpBVeE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790081576; c=relaxed/simple; bh=Jae59hpYchWjFu5lmM2YnvXbv7hvGTzJEokKNdRbnnA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=ZXMwfKYYM3+r68K5CZ9zg8nz6b20Q3weilXLYkL1LBFbxy18QSCaRun0h2jJqlIVM7AVGTN7cMjMPZ+xlzHa/WnBHqwlk/UznkcH/yggjRFv/U5yFK9+UJ9gmMGskKlJ+NnTUt371K+wqdT+UwBdrYmQ6zByj0wkGCebKtV1SOA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=nxPbQTi7; arc=none smtp.client-ip=91.218.175.238 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="nxPbQTi7" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=Jae59hpYchWjFu5lmM2YnvXbv7hvGTzJEokKNdRbnnA=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1790081572; v=1; x=1790686372; b=nxPbQTi79vF9CUl8eezgYLh9Qdy4s+5kv/DBz2cICTmalmIeDKUvG2BEryNN6gi977Rncrqu nEljd/+ZzxjWRbYuUAbB96sHJ5aihuI9vrv8a/Ez0OUqO3HmKHeShOmA3tTINyauiwqBO7MeSU6 77xt9COVa8rCdWe+OlJtl5s0= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id d19d6af701ceeb03; Tue, 22 Sep 2026 12:52:52 +0000 X-Mizu-Trace-ID: d19d6af701ceeb03 X-Migadu-Flow: FLOW_OUT Message-ID: Date: Tue, 22 Sep 2026 13:52:45 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RESEND v7 07/29] x86: mm: add PMD swap-exclusive helpers To: Kiryl Shutsemau Cc: Andrew Morton , david@kernel.org, chrisl@kernel.org, kasong@tencent.com, ljs@kernel.org, ziy@nvidia.com, linux-mm@kvack.org, ying.huang@linux.alibaba.com, Baoquan He , willy@infradead.org, youngjun.park@lge.com, hannes@cmpxchg.org, riel@surriel.com, shakeel.butt@linux.dev, alex@ghiti.fr, baohua@kernel.org, dev.jain@arm.com, baolin.wang@linux.alibaba.com, Nico Pache , "Liam R. Howlett" , ryan.roberts@arm.com, Vlastimil Babka , lance.yang@linux.dev, linux-kernel@vger.kernel.org, nphamcs@gmail.com, shikemeng@huaweicloud.com, yosry@kernel.org, qi.zheng@linux.dev, luizcap@redhat.com, kernel-team@meta.com, Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org References: <20260914122950.3283997-1-usama.arif@linux.dev> <20260914122950.3283997-8-usama.arif@linux.dev> Content-Language: en-US From: Usama Arif In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 16/09/2026 15:31, Kiryl Shutsemau wrote: > On Mon, Sep 14, 2026 at 05:27:57AM -0700, Usama Arif wrote: >> A later patch keeps a PMD-mapped anonymous THP mapped by a PMD across the >> swap round-trip, so PG_anon_exclusive now has to survive in a swap PMD and >> not just in a swap PTE. >> >> x86-64 encodes a swap PMD exactly like a swap PTE, so the new helpers reuse >> _PAGE_SWP_EXCLUSIVE, bit 3, which the swap-entry layout already reserves >> for PG_anon_exclusive. 32-bit x86 aliases that bit to _PAGE_PSE and does >> not select ARCH_HAS_PMD_SOFTLEAVES. >> >> Cc: Thomas Gleixner >> Cc: Ingo Molnar >> Cc: Borislav Petkov >> Cc: Dave Hansen >> Cc: x86@kernel.org >> Signed-off-by: Usama Arif >> --- >> arch/x86/include/asm/pgtable.h | 17 +++++++++++++++++ >> 1 file changed, 17 insertions(+) >> >> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >> index d551120a7c889..a2d1cd03cba23 100644 >> --- a/arch/x86/include/asm/pgtable.h >> +++ b/arch/x86/include/asm/pgtable.h >> @@ -1525,6 +1525,23 @@ static inline pte_t pte_swp_clear_exclusive(pte_t pte) >> return pte_clear_flags(pte, _PAGE_SWP_EXCLUSIVE); >> } >> >> +#ifdef CONFIG_ARCH_HAS_PMD_SOFTLEAVES >> +static inline pmd_t pmd_swp_mkexclusive(pmd_t pmd) >> +{ >> + return pmd_set_flags(pmd, _PAGE_SWP_EXCLUSIVE); >> +} >> + >> +static inline bool pmd_swp_exclusive(pmd_t pmd) >> +{ >> + return pmd_flags(pmd) & _PAGE_SWP_EXCLUSIVE; >> +} >> + >> +static inline pmd_t pmd_swp_clear_exclusive(pmd_t pmd) >> +{ >> + return pmd_clear_flags(pmd, _PAGE_SWP_EXCLUSIVE); >> +} >> +#endif >> + > > I was about to comment that it is broken on 32-bit as > _PAGE_SWP_EXCLUSIVE there is _PAGE_PSE which would make exclusive swap > entries pmd_present(). But CONFIG_ARCH_HAS_PMD_SOFTLEAVES is only > selected for X86_64. > > Do we want some BUILD_BUG_ON() to catch if anyone would try to enable > it for 32-bit machines? I added static_assert(_PAGE_SWP_EXCLUSIVE != _PAGE_PSE); Thanks for the review! > > Otherwise: > > Reviewed-by: Kiryl Shutsemau (Meta) > >> #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY >> static inline pte_t pte_swp_mksoft_dirty(pte_t pte) >> { >> -- >> 2.53.0-Meta >> >