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 A8465C88E72 for ; Thu, 17 Sep 2026 15:37:49 +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=E4Npou4OSCYsiACCFsF6vY+bxlBMBxovk5l1RYnnJok=; b=DhjjduTEsBaF6oZjw5oHpBR8sU d8h15BZunorYDkuCLpQXnUyzUbbFA4wZbclx5d47SsxmhcwssEnHUiOtY+Bwv6ErvNerU65ekimqf 2xNpdMJ5P11RjT3S0Ouy644dk+3ZBLH2HeANwGH2ivO3DzboaxtaSNaPIu+5A8O00F6Eq4d9If5FS dCuE6RuxIR3AZP9iaalm7QipJhBYl2bxnmHp3s3LLE7Fj61OmyxEB1zG8gsBZo+UWwon8YgTVsVLj NUuMNyrPNwslZ4k/yApEi7VXqZOfSBVaUahzaP0atM/gPZiq8ImM7YiaKWX09d7Mq+ye97pOJ4G8e zeINwDjg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7D6v-0000000BXAP-2wUH; Thu, 17 Sep 2026 14:29:13 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1x7D6t-0000000BXAH-2vIk for linux-arm-kernel@lists.infradead.org; Thu, 17 Sep 2026 14:29:11 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id C2D1260052; Thu, 17 Sep 2026 14:29:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 729B21F000FF; Thu, 17 Sep 2026 14:29:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789655350; bh=E4Npou4OSCYsiACCFsF6vY+bxlBMBxovk5l1RYnnJok=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=hSIYyGMMHMmQot00sRLbJTgSrCB2ACUPQCPABeM0mlNFQDm+1z2GdtiKRII3qr10L nSIPgNwF1oXIIqUouKByw06Pr2MJB+7ckaEKZL0oeswPNfNvEKpzLYM6StjAsQCNt1 TtzzFewWF295evlI7CQGsAKK1A8t5mbRNGXnOnaUcV5tbSUjB9u0EnulOdglhQ4w2e dbq8b1aXuJB8KZS0XIByC6TRBtf8rzThnyopZklZv0JOHfxmrOr84xBwpyAXqow4r7 jOOiY6jhMImOtaTmKGiqc1KJmWgwu2jyU/GD8xL9bUDRGGJJZiTWf5ijkAZdmOejWz It7Nd+rmDJX7A== Date: Thu, 17 Sep 2026 17:29:04 +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? > - what happens when removing a non-page aligned region from memblock > that intersects with a (page aligned) no-map region? Another thing is that maybe we should force memblock.memory only to page aligned ranges. x86 uses memblock_trim_memory() for that since, like, forever. -- Sincerely yours, Mike.