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b=bk0e4BNXD6Yt7f4mKRojtk8ruecTagIIEG5ZStNZDXOJpUmflQARjCnJhnRz+paso roEnmnTZ/3YOwcWe24nYpk6kuNpdCBLakaiK6zYS+gzTDqq+QmsSOQ65c1vUMYn2/E tCcBDdNjvnqRhAw2ZL2IpfCQ5+NnBVg9CogjjWTrHur7cL+kyD3ZDma3KswYbArbZI zFuoEqE5eTB6wRIQI5VVRjH5zWbWsl/Yoy2UtK0na15HGAg0ukDR9WwlFRSKyB8Q5H ncK6y9yjMjyAMKOjFOa4svGHzlTF37gjH09YIdRl2GFIuzKWmdirlkLYsXuRmpqj8x lXfm1lzH96/Zg== Date: Fri, 10 Apr 2026 10:59:49 +0300 From: Mike Rapoport To: Evangelos Petrongonas Cc: Alexander Graf , Pasha Tatashin , Pratyush Yadav , Rob Herring , Saravana Kannan , Changyuan Lyu , Andrew Morton , kexec@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, nh-open-source@amazon.com Subject: Re: [PATCH v2] kho: skip KHO for crash kernel Message-ID: References: <20260410011609.1103-1-epetron@amazon.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260410011609.1103-1-epetron@amazon.de> X-Rspamd-Queue-Id: B2A27A0005 X-Stat-Signature: 6qwkcbm7qkawr3s3h8iqrxgux5aqnxbg X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1775807997-640355 X-HE-Meta: U2FsdGVkX1/bR2FL/+1BFvIt5nmzoESR85jBIyfqHRDLw7kwlKtiQ8PVXI2Dw8v71MigKCTaqsQei41GoVDX0sehGMZDJqf8b+xRbvvFBJlyKA1MHYN03uVDUaETkymbvL6qziD1XRcDE39rNxkFpkpoB3Q5icb1oX9Toa0eW6fChavGxjHPXjnm+nA4OAIXaIP7+v2dbhB2t2ml3qZnGas8Lg+JEYNjWwnf51eujES+1DLfu1xRsnI+Bgjo49DvKl5JU5AfMCneIRtLazjh5xDQhgRGkrTKKGUtr1CRg4RLXwDKR2FXjR2KPs0NR7WzQPSSxtapsJOAwef3i5U33tsxzFhcLPVXMIVofiJJf2sIZ8NSytebjn+eZPG76wZ0lCBLXv/dZQ2pVeEpjRKmev82nevZUp082GeUHbu7UAntTq9qZroUBTUmNrz/dhTreRwB+m3jbN0JQGhIxHktzN+6OWlCTlK5KKjomjYFU3Y6ODBD7C3nX+tAxTfD+QeCD+TPK7lCwhkoQ1xnQORvuMR/DJmLDo0IZT7nRYAhutsWn6VVlw/1kzPJd0R8mIP2NDoY9YtwT0Lr+Gb/wTyJmuH0O1eunBjfH1E2XlPQSmJKF88F7JQOeCUdFnt6YuAFPl5kTpKWao5q3sp94nlpxxX+FkhTakwbfZyPuYgYuj14oRc/zv0CCHgy4lMT3HQmdxBCMhnq4T1ZOm1mR88cwE3b9+aC9kwTadkO9+xvrT4zUGsPGcwZ36un/V9QW4Tja1Qw0T7H811xC8fBCXgo0bkvuiklbYrt0iZZ3KNiCZuCZWGm1rTiQMaWY77NIOFKju5cvXxoHTNni3h6x48Gm99jJvln0vitumOS2EbAuvVR92eJtnhl7kaYVPqfmYx4Klfw+AWaxr7To5bJKspmjqNo+TbPCD3B9QR9/SKxi4Byr6rZXfAXufKxsnhvJtzNkB11PINCTTTS2oYhuy+ Nyska9iR pobUPWxJjGvXlHEWI5ZGweegeV5Zc7Bi2Hm41yy+VGVKkpKSxU0f/7tCcMPy8AaTOsr32yojtwonIYPXRTLlNam+AWVj0kYvFryyf4K7u6PrivfPs83Frc/cKyeWPQnXDffiltEez92/15uf1/4QUjhcIGR63wYpMXPjm3lcBYBcide5ha55JZl0EnNNh/0IqDCYbs4PRdnpa0L8FfaQc72EDp4+sqckvs+ze6cC+0JK1GPti5j9xj1S1Jg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Apr 10, 2026 at 01:16:05AM +0000, Evangelos Petrongonas wrote: > kho_fill_kimage() unconditionally populates the kimage with KHO > metadata for every kexec image type. When the image is a crash kernel, > this can be problematic as the crash kernel can run in a small reserved > region and the KHO scratch areas can sit outside it. > The crash kernel then faults during kho_memory_init() when it > tries phys_to_virt() on the KHO FDT address: > > Unable to handle kernel paging request at virtual address xxxxxxxx > ... > fdt_offset_ptr+... > fdt_check_node_offset_+... > fdt_first_property_offset+... > fdt_get_property_namelen_+... > fdt_getprop+... > kho_memory_init+... > mm_core_init+... > start_kernel+... > > kho_locate_mem_hole() already skips KHO logic for KEXEC_TYPE_CRASH > images, but kho_fill_kimage() was missing the same guard. As > kho_fill_kimage() is the single point that populates image->kho.fdt > and image->kho.scratch, fixing it here is sufficient for both arm64 > and x86 as the FDT and boot_params path are bailing out when these > fields are unset. > > Fixes: d7255959b69a ("kho: allow kexec load before KHO finalization") > Signed-off-by: Evangelos Petrongonas Reviewed-by: Mike Rapoport (Microsoft) > --- > > v2: Per Mike's review [1], move the guard into kho_fill_kimage() instead > of patching the arch-level producers and consumers. This fixes > both arm64 and x86 in one place and avoids redundant checks. Tested again. > > Note regarding backporting > The offending commit was deployed with 6.19. The only other supported > kernel version with 6.18, unless I miss someting uses > ``` > if (!kho_out.finalized) > ``` > which in the case of crash kernel it shouldn't be finalised. Yes, this seems about right :) The only released kernel that has this issue is v6.19 and it will be EOL in less than a week. > [1] https://lore.kernel.org/all/ade2ExpM8ROXV-vy@kernel.org/ > > kernel/liveupdate/kexec_handover.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > index cc68a3692905..1029fe8778f2 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -1551,7 +1551,7 @@ int kho_fill_kimage(struct kimage *image) > int err = 0; > struct kexec_buf scratch; > > - if (!kho_enable) > + if (!kho_enable || image->type == KEXEC_TYPE_CRASH) > return 0; > > image->kho.fdt = virt_to_phys(kho_out.fdt); > -- > 2.47.3 > > > > > Amazon Web Services Development Center Germany GmbH > Tamara-Danz-Str. 13 > 10243 Berlin > Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger > Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B > Sitz: Berlin > Ust-ID: DE 365 538 597 > -- Sincerely yours, Mike.