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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1763990758; bh=V3pNaPV0kKnax3zGGnv1AnsUhY0LbnCFMQ5OaJ21pJ0=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=CYTjpF4IqP6zSOrYyA371vjXfNJC7bd00OTA1CE5rpfF6muw17PEE2UxeKCi15eLq PQxSKfXFIgFWxfzPAYgfMtTjyX5g80i197Ya+zrjB7Sw9Cyy+NCIkFgg7jfzi5qcNW b41ni0lnkTl61chQhTW85fIs872WP5c4GTYZzcUuPdAI1GDVpCZrY9uEhS+l5nDImj l0XWnjCK579Po2HYhTBgnPZthYY/E19895OxnfPmAoIi8XVq96ZrczHVKeplcZsaDA USypK0KqHUs4xEfdivciT9uT3FLODj0pbwolLV7dU9zvVaL6JKk6X10jIl6OpLZxVN I1Nmy/oMt9gXA== From: Pratyush Yadav To: Pratyush Yadav Cc: ranxiaokai627@163.com, rppt@kernel.org, akpm@linux-foundation.org, catalin.marinas@arm.com, changyuanl@google.com, graf@amazon.com, pasha.tatashin@soleen.com, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ran.xiaokai@zte.com.cn Subject: Re: [PATCH v3] KHO: Fix boot failure due to kmemleak access to non-PRESENT pages In-Reply-To: (Pratyush Yadav's message of "Mon, 24 Nov 2025 13:16:55 +0100") References: <20251124025943.94469-1-ranxiaokai627@163.com> Date: Mon, 24 Nov 2025 14:25:55 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: E6ED718000C X-Stat-Signature: ptn57od9dtjo68huokeqf1qmg9w81rrt X-Rspam-User: X-HE-Tag: 1763990759-701509 X-HE-Meta: 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 RjbKtPYL FaF3hGU1c//lzyiBdJ3S7EUdXFaA4MWR4POXlF3W2X0c5DDosdXC3X/2z/pfDzxBfqixIBx2HIed//aO5wtFXhWm6oaxhU3dd/mkxa5/YCIG65BYZVf+vmbzBgp29wjgcMxWGgHpwuTfMyqrDOxanR93qFbgGhyi8yCMfINEXqcN+HzqgJ3clOWgVesQhzSeb504FhDeXmebHh0K521Jy0fIJ80G2gj6MXu0loQ1Fy8BC4eCpmAqINJovo+IXd4PQBFWoLAtZgcYrwma5AG0YidlHsw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Nov 24 2025, Pratyush Yadav wrote: > On Mon, Nov 24 2025, ranxiaokai627@163.com wrote: > >> From: Ran Xiaokai >> >> When booting with debug_pagealloc=on while having: >> CONFIG_KEXEC_HANDOVER_ENABLE_DEFAULT=y >> CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=n >> the system fails to boot due to page faults during kmemleak scanning. >> >> This occurs because: >> With debug_pagealloc is enabled, __free_pages() invokes >> debug_pagealloc_unmap_pages(), clearing the _PAGE_PRESENT bit for >> freed pages in the kernel page table. >> KHO scratch areas are allocated from memblock and noted by kmemleak. But >> these areas don't remain reserved but released later to the page allocator >> using init_cma_reserved_pageblock(). This causes subsequent kmemleak scans >> access non-PRESENT pages, leading to fatal page faults. >> >> Mark scratch areas with kmemleak_ignore_phys() after they are allocated >> from memblock to exclude them from kmemleak scanning before they are >> released to buddy allocator to fix this. >> >> Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers") >> Signed-off-by: Ran Xiaokai >> Reviewed-by: Mike Rapoport (Microsoft) >> --- >> kernel/liveupdate/kexec_handover.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c >> index 224bdf5becb6..c729d455ee7b 100644 >> --- a/kernel/liveupdate/kexec_handover.c >> +++ b/kernel/liveupdate/kexec_handover.c >> @@ -11,6 +11,7 @@ >> >> #include >> #include >> +#include >> #include >> #include >> #include >> @@ -1369,6 +1370,7 @@ static __init int kho_init(void) >> unsigned long count = kho_scratch[i].size >> PAGE_SHIFT; >> unsigned long pfn; >> >> + kmemleak_ignore_phys(kho_scratch[i].addr); > > Can you please put the explanation you gave in [0] for why this is not > necessary in KHO boot as a comment here? And also an explanation of why this is necessary in the first place. You do explain that in the commit message, but a shorter version as a comment will make this a lot easier to understand instead of having to dig through git history. [...] -- Regards, Pratyush Yadav