From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 C6B6A3C988E; Wed, 19 Aug 2026 07:13:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787123635; cv=none; b=tYoDCIqPSx3+cToHB/G8eGLK49JULu7U9Hje1CilzFAGldhFteYJV2r3Bzl0O+dRCFwcMjaTNFd2or7YJgM0+CfxImlIoHpCZAP/4yZhFRRhSUPLe2didQV+GJvm439f0Ca9Ue+/58NGAbe9O0F4BgupOlkTmIh5Njs0WFQ3b/k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787123635; c=relaxed/simple; bh=xOOSAt4DTvCOYpoeTuMomWNTzyBZPisCmemg7TCeUEI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=BVodE91hVg+kkqz/nUloXGsKWinj0SH1seRJRulB7MjFOw1Db5oQy8xP8JHI5TriUHr0Y+RoCNjOV0J0Kqbss6+9jU3AmLSvk79lU13+qjO8wJuNc3F8hrxiQ2r2F8shGz/petx5vDyLaOb7AhXghBMrJ4LtvCPVcijBYkMcIYY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=jJV0OzwV; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="jJV0OzwV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8FCAB1F000E9; Wed, 19 Aug 2026 07:13:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787123634; bh=MEh93umEkAdwM7W7h5DMLx7l0jri6Tex4Ey3QmOKRt0=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=jJV0OzwVbpNuL1O7IKYFMOfkJNn5jUunHF3YbR6s3DRCL2TlLVhLPBotWdiGtRokA tmvHyqyp+imK+t1Fq3nxpk977s16W+HIjEKyInWVUV1oA//lPAb6rPWocpZquA5Ccm bgwCf3DzoBtBiJCPGwlFz9HjCr/lq2MMwhpgdxHoSsupRhmU3NSJ07HL6c5BUc2jmQ uN/InEQopdQkSXzswZqrN8YxkDoenas2ccCQodY70U8cWRig2OBGou4vh1U4PakYtX vAKsses0e/ZiFmKxHArYa8yhDZVE4w8x5VBUX22681OzmQsFslwRWWGAKw1WggWAbV zsPrgq11T43eA== Date: Wed, 19 Aug 2026 10:13:38 +0300 From: Mike Rapoport To: Brendan Jackman Cc: Andrew Morton , Adrian =?utf-8?Q?Barna=C5=9B?= , Albert Ou , Alexander Gordeev , Alexandre Ghiti , Andy Lutomirski , Borislav Petkov , Catalin Marinas , Christian Borntraeger , Dave Hansen , David Hildenbrand , Gerald Schaefer , Heiko Carstens , Huacai Chen , Ingo Molnar , Len Brown , Palmer Dabbelt , Paul Walmsley , Pavel Machek , Peter Zijlstra , "H. Peter Anvin" , "Rafael J. Wysocki" , Ryan Roberts , Sven Schnelle , Thomas Gleixner , Uladzislau Rezki , Vasily Gorbik , WANG Xuerui , Will Deacon , x86@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-pm@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, loongarch@lists.linux.dev, yosry@kernel.org Subject: Re: [PATCH 6/6] Revert "arch: introduce set_direct_map_valid_noflush()" Message-ID: References: <20260816-execmem-set-vm-perms-v0-2-v1-0-90944a3ad43f@kernel.org> <20260816-execmem-set-vm-perms-v0-2-v1-6-90944a3ad43f@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Mon, Aug 17, 2026 at 05:14:19PM +0200, Brendan Jackman wrote: > On Sun Aug 16, 2026 at 12:59 PM CEST, Mike Rapoport (Microsoft) wrote: > > Commit 0c6378a71574 ("arch: introduce set_direct_map_valid_noflush()") > > added set_direct_map_valid_noflush() to allow updating the direct map > > for a physically contiguous range in execmem. > > > > As Brendan recently pointed out [1], this API is confusing because on > > arm64 it means that is sets VALID bit in ptes, while on other > > architectures it is an analog of set_direct_map_default_noflush(). > > > > The only user of set_direct_map_valid_noflush() was execmem's ROX cache > > freeing path and it was switched to utilize VM_FLUSH_RESET_PERMS for > > resetting permissions of the direct map alias. > > > > With the last user gone and with set_direct_map_{invalid,default}_noflush() > > accepting number of pages as a parameter, set_direct_map_valid_noflush() > > become a copy of set_memory_valid() on arm64 and a duplicate of > > set_direct_map_{invalid,default}_noflush() on other architecture, it is > > safe to remove set_direct_map_valid_noflush(). > > > > Also drop a stale comment in arm64::__kernel_map_pages() that Linus > > bothered to add when merging changes containing set_direct_map_valid_noflush() > > to his tree. > > > > This reverts commit 0c6378a71574daa6cd1534ad42a956e3262756c7. > > > > [1] https://lore.kernel.org/all/DJ69RCVRBO0Y.3JCYSW50IC4RC@linux.dev > > > > Signed-off-by: Mike Rapoport (Microsoft) > > So basically the big issue here is specifically that > set_direct_map_valid_noflush(..., true) is special on arm64 and not x86. More precisely arm64 differers from all the rest. > And we fix that by jut deleting the API. SGTM! > > The other issue I can see here is that set_direct_map_invalid_noflush() > clears RW on x86 but doesn't set RDONLY on arm64. So if you unmap > something using set_direct_map_invalid_noflush(), then map it again > using something other than set_direct_map_default_noflush(), you get > different behaviour between the archs. > > I think the answer to that is probably: doing that is a bug, i.e. > _invalid_noflush() and _default_noflush() are a pair that you have to > use together. But I haven't checked if this is currently the case. Maybe > it would still make sense to just align these fully? All set_memory + set_direct_map functions very much rely on caller to know how to use them right. There were only handful of users outside of arch/ so it was kinda sustainable. With the increased demand for those, security and whatnot, the whole bunch of set_memory functions needs some love. > Anyway, aside from all this yapping, getting rid of _valid_noflush() > seems like an unambiguous win here so thanks for the cleanup! > > Reviewed-by: Brendan Jackman -- Sincerely yours, Mike.