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 9F2BCD10375 for ; Thu, 27 Nov 2025 05:42:03 +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-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=pkdPotq4J7OiZrvFjNi/z6yKQ2bfC1Ibf8nUJvrfels=; b=CBdIGutsF6lbWvQOU/iObEIj2B TAZ5J1+PcRJ6+w7Q4Jzhv1barymgMr4AlzkqjFaWyzYG+AWnTLkwO7gcULpH8spTEj3UVne4rHB+W XHTT5w4TquDBEaPY5KrUCB4yRNatAc+c9BqGR1Q/jPrhicbBx9TFviEQU7zc5MahmlDsi1ICVCFUU VT7sIg8AQm/zCQOB9g98+zozEyAA1/kJTWWya/n3LE/sWbC96F6CmhIljsMhfRaqyakc5Iu/59jHY ve9yPPmBq/WENseOHy20ZHUdgFQZ9I+ihVccdKV7YetkIjIFkdXU3H1YR5p+8SsN4wj4zqFa7Ml/F HR/TtSDg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vOUlO-0000000G0Qq-3Mjp; Thu, 27 Nov 2025 05:41:54 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vOUl1-0000000G0PY-2uEo for linux-arm-kernel@lists.infradead.org; Thu, 27 Nov 2025 05:41:53 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 027EC1477; Wed, 26 Nov 2025 21:41:22 -0800 (PST) Received: from [10.163.48.177] (unknown [10.163.48.177]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B54343F66E; Wed, 26 Nov 2025 21:41:26 -0800 (PST) Message-ID: Date: Thu, 27 Nov 2025 11:11:20 +0530 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] arm64: mm: Fix kexec failure after pte_mkwrite_novma() change To: Jianpeng Chang , catalin.marinas@arm.com, will@kernel.org, ardb@kernel.org, ying.huang@linux.alibaba.com Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20251127034350.3600454-1-jianpeng.chang.cn@windriver.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <20251127034350.3600454-1-jianpeng.chang.cn@windriver.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251126_214131_857365_FDBFF5B3 X-CRM114-Status: GOOD ( 25.96 ) 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 27/11/25 9:13 AM, Jianpeng Chang wrote: > 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()") > 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. > */ Hence pte_mkwrite_novma() helper cannot be used here as would have normally expected. Might be good idea to add to the above comment. > - __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); > } 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); Probably better to move pte_mkvalid() just after clearing PTE_RDONLY. > + pte = set_pte_bit(pte, __pgprot(PTE_WRITE)); > + pte = clear_pte_bit(pte, __pgprot(PTE_RDONLY)); > + __set_pte(dst_ptep, pte); > } > } > Just wondering if it would be worth adding a local helper for the set PTE_WRITE --> clear PTR_RDONLY sequence describing its difference with now updated pte_mkwrite_novma() helper with the earlier comment.