From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F0339C982D1 for ; Thu, 17 Sep 2026 13:14:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To: Content-Transfer-Encoding:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=PNgpEuFxkLpwQVUTRb/HejZ0tN6jXsHgSl5ZBTQhmMs=; b=Wii6z21aiv3T8O++IN1ouCJ6dt obIQcGo/joNwrGzH83nzjCGNYKYOWptyngVnyLW53sF+rsuH1FJSfyXxoAELcdm+zaJ7hx8TbFivh kax+puHm3sAJdI+rJ2PG2GRRei9uEHLx7mf1dU+/O5ghQcJxxcF+KweNRWQ+QBartVv/l1UeuwvnE 5NgVFzhe2RkaakydKW15wdUQWlJdpT9tR+EMjNxLTh7p9lKME41jBnClLYU4jZ+s0GrVMqwViFdpm uWh3mk8M69H72QG6y4I8wVTfFrwVSLOJCy4N2hDHvvHkSyn+hRWzBpI4kLwW5qjjfFbqHrP0W/3mY ErxCg+Iw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7Bw9-0000000BNWt-1DkC; Thu, 17 Sep 2026 13:14:01 +0000 Received: from tor.source.kernel.org ([172.105.4.254]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7Bw6-0000000BNWV-3gjz for linux-arm-kernel@lists.infradead.org; Thu, 17 Sep 2026 13:13:59 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id F4188600D4; Thu, 17 Sep 2026 13:13:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3EAF31F000FF; Thu, 17 Sep 2026 13:13:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789650837; bh=PNgpEuFxkLpwQVUTRb/HejZ0tN6jXsHgSl5ZBTQhmMs=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=n+iXY1iBZUiYhHQNX3M/KedAqPFUcruQCCfT+Jk8iObh88EdMCvSpWvKnffaB02Xo agJz757+ipCx0fEOOG9hs/rCIzNI1q9suqvwygogxGEIGLE1C9Zr9c002GK9RFs+o5 ttBilpJFfy0p2Cg64LZ6qB2WnKg8T5fCVz/QvO4c4TShM+7kpLtOG1g1A6GItLtxMa CiNmBKk3znnL5XXHqG/vKtJxD1fIiuioPRKURvHKoc+5NT5U2irwDk2suHKuDlcKuE lmp/qV5ugvCwtOCqOt7vu9JahWqrm0GzUV7ZWQ+aIVe7VTilrQkBsQ1pfxsrRxW/nE GuFCCseLX91iA== Date: Thu, 17 Sep 2026 16:13:51 +0300 From: Mike Rapoport To: Ard Biesheuvel Cc: Vladimir Murzin , linux-arm-kernel@lists.infradead.org, Catalin Marinas , Will Deacon , liulhong617 Subject: Re: [PATCH] arm64: mm: Fix pfn_is_map_memory() misreporting mapped memory Message-ID: References: <20260908162033.74509-1-vladimir.murzin@arm.com> <947a1506-dfe4-4906-9673-6a7227946433@app.fastmail.com> <01f1f6d9-e10f-43f9-b731-f6393010a11c@app.fastmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <01f1f6d9-e10f-43f9-b731-f6393010a11c@app.fastmail.com> 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Sep 17, 2026 at 02:34:57PM +0200, Ard Biesheuvel wrote: > On Thu, 17 Sep 2026, at 14:26, Vladimir Murzin wrote: > > On 9/16/26 11:13, Ard Biesheuvel wrote: > >> (cc Mike) > >> > >> On Tue, 8 Sep 2026, at 18:20, Vladimir Murzin wrote: > >>> Commit 7ace06a01efa ("arm64: mm: fix accidental linear mapping of > >>> no-map reserved memory") removed sub-page no-map regions from the > >>> linear mapping. However, pfn_is_map_memory() can still report that > >>> such a region is mapped. > >>> > >>> For instance, with 64K pages, say we have > >>> > >>> normal: ...–0xa2007fff > >>> no-map: 0xa2008000–0xa200ffff > >>> normal: 0xa2010000–... > >>> > >>> The range 0xa2000000–0xa200ffff is not linearly mapped, but > >>> pfn_is_map_memory(__phys_to_pfn(0xa2008000)) aligns the address to > >>> page granularity and passes 0xa2000000 to memblock_is_map_memory(). > >>> That address belongs to the preceding normal memblock region, so the > >>> no-map region is ignored and the function returns true. > >>> > >>> Fix that by checking if entire page is subset of memory block. > >>> > >>> Fixes: 7ace06a01efa ("arm64: mm: fix accidental linear mapping of > >>> no-map reserved memory") > >>> Assisted-by: LLM > >>> Signed-off-by: Vladimir Murzin > >>> --- > >>> arch/arm64/mm/init.c | 3 ++- > >>> 1 file changed, 2 insertions(+), 1 deletion(-) > >>> > >>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > >>> index fbf215ecc7d0..5da80e1e1727 100644 > >>> --- a/arch/arm64/mm/init.c > >>> +++ b/arch/arm64/mm/init.c > >>> @@ -172,7 +172,8 @@ int pfn_is_map_memory(unsigned long pfn) > >>> if (PHYS_PFN(addr) != pfn) > >>> return 0; > >>> > >>> - return memblock_is_map_memory(addr); > >>> + return memblock_is_region_memory(addr, PAGE_SIZE) && > >>> + memblock_is_map_memory(addr); > >>> } > >>> EXPORT_SYMBOL(pfn_is_map_memory); > >>> > >> memblock_is_region_memory() only tells you whether the range in > >> question is covered by a single entry in memblock.memory.regions[]. > >> > >> memblock has other flags, which may or may not be set on sub-page > >> regions too. So I don't think this is the right solution in the > >> general case, even if it fixes your example. > >> > > > > Ack. > > > >> Given that the no-map attribute fundamentally only applies to page > >> granular regions, it would make sense to round those outwards > >> whenever they are created. > >> > >> --- a/mm/memblock.c > >> +++ b/mm/memblock.c > >> @@ -1119,6 +1119,10 @@ > >> int __init_memblock memblock_mark_nomap(phys_addr_t base, phys_addr_t size) > >> { > >> + phys_addr_t end = PAGE_ALIGN(base + size); > >> + > >> + base &= PAGE_MASK; > >> + size = end - base; > >> return memblock_setclr_flag(&memblock.memory, base, size, 1, MEMBLOCK_NOMAP); > >> } > >> > >> > > > > Should the same be applied to memblock_clear_nomap()? > > > > Yes. > > > This is indeed much nicer way to fix the problem! Now, when no-map is > > rounded outwards, do we still need 7ace06a01efa? > > > > Probably not, but there are some corner cases to consider before we > go down this route: > - what happens when marking a range no-map where the outward rounding > would exceed the limits of the existing memblock memory range? AFAIR it's fine, memblock_isolate will clamp the update. Didn't check the code though. > - what happens when removing a non-page aligned region from memblock > that intersects with a (page aligned) no-map region? It will make the nomap region non-page aligned. -- Sincerely yours, Mike.