From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-97.freemail.mail.aliyun.com (out30-97.freemail.mail.aliyun.com [115.124.30.97]) (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 2800C2E7658 for ; Fri, 28 Nov 2025 09:32:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.97 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764322362; cv=none; b=AWOhF2qePdDejJHVX9NvcPNSxqJ5BqAILXmVZ1U5A3F0H1odCjSsE8IVda6jjLG8uFTAJHCQ4ly2rex0zb4cDgDcidTQiUfdzePR9WwmVegeujUUk+jilba2AA1B9K6S58npCO5Kzs4pkOF+5Ko9WJcjTeHhp6e47IUvR06QIfU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764322362; c=relaxed/simple; bh=21x3rlKMVF4R/iaoVUOEVzNe4TytD84sHYFKRiRNAEM=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=LejkVI4WshpS1oGPiMrUCjLU0D3OpJS62bj2pmIaO2rhfOTX38Iu9smes65Obkw7L8wA1XLNy1d4Wy1kMb5hAUkw62FtfxBYBc3/dHF6PQ+V2m/9w0aVAqO6KVJoWFlJJ3ouW4igEymtjPgNvvSk6mspwZpm591Nf3RTQ54lClI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=l/4AYQPL; arc=none smtp.client-ip=115.124.30.97 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="l/4AYQPL" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1764322350; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type; bh=TnMExoxTnMaCJz7/CnGcGQbAG/H1JHbfw3uQYHzjP7o=; b=l/4AYQPL97vjW/AWHQuo1EFZCPe9pXv6L5VzooxS0iexXi0dbsPbAOdnH/4qFQRkmqdD9jmMRVQPqKx7r77wrUY3WPkxNTchx/z8lQ/mGtd/BkmUCPc6hl5h9falk4pZo1beeuaDBCTF1hIGQjUiowhrwrBln7tlH05dHE8jr4g= 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) 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=ascii 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