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 0550ECFD376 for ; Fri, 28 Nov 2025 09:32:57 +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:Content-Type:MIME-Version: Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=TnMExoxTnMaCJz7/CnGcGQbAG/H1JHbfw3uQYHzjP7o=; b=TBugmwTErBm/hnon+Xn0WU7QaU SJgocHr/7jO6YKqEHYCi6UVbKgVaxMt4QrHUN9tYJgC6lGLWitMAQSDZdzbfkvX7Akc7CbPeivKiN /GXzilSW0HEnhPw9SkjuC58pL5P2HItmcrx0qrRdYyTBLVuEeO+1tHxZNDQ+m6swqXh/JyQcEdkMI c6vS1Q90X/xU757Zrt6Kz8tWTuaJElWZN4Z/Gx2S0S7hLmwNhSKAIXxA02JRrJQ4fa/KWlnii37Tt zvdDttd6hfjyBRTKf6SUwZ7/lcxW4vkTefgpbqllrhhZp270iKdDXgEb12ncu+qqAoPV3GyHqdvZv B+MAgoRg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vOuqI-00000000EQs-0GI2; Fri, 28 Nov 2025 09:32:42 +0000 Received: from out30-119.freemail.mail.aliyun.com ([115.124.30.119]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vOuqE-00000000EQD-0hl1 for linux-arm-kernel@lists.infradead.org; Fri, 28 Nov 2025 09:32:40 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1764322352; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type; bh=TnMExoxTnMaCJz7/CnGcGQbAG/H1JHbfw3uQYHzjP7o=; b=sLG10+NMscQ0YDGn/3GPIEtTcTD0+39jcItK/+nADsNhK/AKctQrCfWTZtsUF9w10Q797qmTqdlnxVkMEPBCMFUHMDo+b6k3NrHpKZ3g1Sw7KK9gwsLXR3Nx+S4nhb17oS7QGLMLB6q7YdGGmoE6LVEQv4MSmVSo1WMihz4nzHw= Received: from DESKTOP-5N7EMDA(mailfrom:ying.huang@linux.alibaba.com fp:SMTPD_---0WtbWYUJ_1764322337 cluster:ay36) by smtp.aliyun-inc.com; Fri, 28 Nov 2025 17:32:29 +0800 From: "Huang, Ying" To: Jianpeng Chang Cc: , , , , , , "Shenhar, Talel" Subject: Re: [PATCH] arm64: mm: Fix kexec failure after pte_mkwrite_novma() change In-Reply-To: <20251127034350.3600454-1-jianpeng.chang.cn@windriver.com> (Jianpeng Chang's message of "Thu, 27 Nov 2025 11:43:50 +0800") References: <20251127034350.3600454-1-jianpeng.chang.cn@windriver.com> Date: Fri, 28 Nov 2025 17:32:17 +0800 Message-ID: <87qztiec4e.fsf@DESKTOP-5N7EMDA> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251128_013238_887014_959201DC X-CRM114-Status: GOOD ( 23.84 ) 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 Hi, Jianpeng, Jianpeng Chang writes: > Commit 143937ca51cc ("arm64, mm: avoid always making PTE dirty in > pte_mkwrite()") modified pte_mkwrite_novma() to only clear PTE_RDONLY > when the page is already dirty (PTE_DIRTY is set). While this optimization > prevents unnecessary dirty page marking in normal memory management paths, > it breaks kexec on some platforms like NXP LS1043. > > The issue occurs in the kexec code path: > 1. machine_kexec_post_load() calls trans_pgd_create_copy() to create a > writable copy of the linear mapping > 2. _copy_pte() calls pte_mkwrite_novma() to ensure all pages in the copy > are writable for the new kernel image copying > 3. With the new logic, clean pages (without PTE_DIRTY) remain read-only > 4. When kexec tries to copy the new kernel image through the linear > mapping, it fails on read-only pages, causing the system to hang > after "Bye!" > > The same issue affects hibernation which uses the same trans_pgd code path. > > Fix this by explicitly clearing PTE_RDONLY in _copy_pte() for both > kexec and hibernation, ensuring all pages in the temporary mapping are > writable regardless of their dirty state. This preserves the original > commit's optimization for normal memory management while fixing the > kexec/hibernation regression. > > Fixes: 143937ca51cc ("arm64, mm: avoid always making PTE dirty in pte_mkwrite()") IMHO, this isn't the right "Fixes" tag. The original _copy_pte() code should be the fixing target. > Signed-off-by: Jianpeng Chang > --- > arch/arm64/mm/trans_pgd.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/mm/trans_pgd.c b/arch/arm64/mm/trans_pgd.c > index 18543b603c77..ad4e5e4fcc91 100644 > --- a/arch/arm64/mm/trans_pgd.c > +++ b/arch/arm64/mm/trans_pgd.c > @@ -40,8 +40,13 @@ static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr) > * Resume will overwrite areas that may be marked > * read only (code, rodata). Clear the RDONLY bit from > * the temporary mappings we use during restore. > + * > + * For kexec/hibernation, we need writable access regardless > + * of the page's dirty state, so force clear PTE_RDONLY. > */ > - __set_pte(dst_ptep, pte_mkwrite_novma(pte)); > + pte = set_pte_bit(pte, __pgprot(PTE_WRITE)); > + pte = clear_pte_bit(pte, __pgprot(PTE_RDONLY)); > + __set_pte(dst_ptep, pte); Why not __set_pte(dst_ptep, pte_mkwrite_novma(pte_mkdirty(pte)); ? > } else if (!pte_none(pte)) { > /* > * debug_pagealloc will removed the PTE_VALID bit if > @@ -57,7 +62,10 @@ static void _copy_pte(pte_t *dst_ptep, pte_t *src_ptep, unsigned long addr) > */ > BUG_ON(!pfn_valid(pte_pfn(pte))); > > - __set_pte(dst_ptep, pte_mkvalid(pte_mkwrite_novma(pte))); > + pte = pte_mkvalid(pte); > + pte = set_pte_bit(pte, __pgprot(PTE_WRITE)); > + pte = clear_pte_bit(pte, __pgprot(PTE_RDONLY)); > + __set_pte(dst_ptep, pte); > } > } --- Best Regards, Huang, Ying