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b=kBi+hiwo08/9mOe6EG2q1yq84Ff8LNY2+8836aE5rlJv1D7bXe9pmypkSuifU3fh3 euRqZaH2A3RgYi3jrloTypTJDJhUPQeUGuHW82BCUf2KyIzhyYeeb658jkRzdPQltK BoOJ1jIdNh+OuaIDgwTIapMLlHt2quM88bE7z6cU25Q0yZjj0ckknCg4fYq3Sf62Yp JwGmvLddaxWMIQextoL4nvDn5pBlZ3oVE+kUdvU0PafBTjXvBXo5Jt8f6KtG2hRHlk dfH3RoNx5t9DgwYtIVGi0xW0bHL/YKRb+rCXX7J5BvokHxLQWzvi15ewRV65ck05tr 6IgfkYlkHBIWw== From: Pratyush Yadav To: Pasha Tatashin Cc: akpm@linux-foundation.org, bhe@redhat.com, rppt@kernel.org, jasonmiu@google.com, arnd@arndb.de, coxu@redhat.com, dave@vasilevsky.ca, ebiggers@google.com, graf@amazon.com, kees@kernel.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org Subject: Re: [PATCH v1 05/13] kho: Always expose output FDT in debugfs In-Reply-To: <20251114155358.2884014-6-pasha.tatashin@soleen.com> (Pasha Tatashin's message of "Fri, 14 Nov 2025 10:53:50 -0500") References: <20251114155358.2884014-1-pasha.tatashin@soleen.com> <20251114155358.2884014-6-pasha.tatashin@soleen.com> Date: Fri, 14 Nov 2025 17:59:32 +0100 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 5B8B22001E X-Stat-Signature: 9bp94p3tomw1kryor8mhagagk4gc9use X-Rspam-User: X-HE-Tag: 1763139577-918789 X-HE-Meta: U2FsdGVkX1/glpCkN5rURI8cdkupcZLRgQDkvQkyM8i/k8E/YCcfeozb8DLBKPPO2hyJrDCqLJXyxmyVRnv/ymy782VqjgwihuX2lsuTGyTj+UzKsVClal2jKrn2A+rQdZSccY3hxVZGDi82y5OdbL0mDdjLdIChrbiS0QVwPe0gVp6jPMLf65d1JUO5Bb65v2OZMZueHmv3o8njDQHuIcwv+7FJLIaqIRRBE8IGf9b0J8yMVm7ChetNUOBiOd7X6SFacgCZgL3D3u12TQr1B3QlPkH+gMPj1TCE0lkzvDHP3JJyYDteWoe3K/H3AAi3tYtPhlZsnMYopXIZkGU7lJGenDzTDlhDTdo2WYY8D4dauFlWQF7oPLpieBs4Y7C05omloUa0/zcN6yd0o+0sb04uEhw8dfzVCX9UdYHeQGZgKH7PvTcFlQwBbmyuI0D9lqJMcr6KjrL2Q/TOkF7eLkQnKbVyL3bosDorUphKn739jeBAqmY1SgjSV67onECGxAT/lCcjgzPuUgLuGL4bo2uvkxi+Q0vJZ25yXN/vX8hLVp+PdoBWt8Zf31OxZuvYuj5Fx6a42Qo3oxFT+AJVuyTytu5eXMV/825H+slDXtV/F7lLQQaI5HRba8ChchXEiGSSKOtUfpjH2CPLykillpBFr407BqK3mFJUyKYEQ4ACG/tWgy1poxoKkOE56VL+sbPbeAHptzLaxuN+0Evh6yEdkJAYRig+ln17Vf3h4aCYAFQ4HSpPRHCXcNAHrmumVxoN2Z0MEpWqKD9kXnmUg3RqkDPRwiYIYLkm9LSsG9LfWwI1rybzm1n5Eo1/yp8bRlYp+jqw5mzTcD+aCRTQ0jrlpD3Z0IZSbfG5zZr7nhTKBHjsputlx5hu7BWEYK4lgWRJq+ZLZfeaqa+MXnTIUN7DKjz5q0xjvPgppz/KsgP5unHuSyhDbX1IaQqp/QqzEzxGefT4gukdJsEGI3r n0t7I2tb +RKV6SvdhFTOZtxTheXDtpD8QAeARhZNlVmlgnPou5ZYBDKXbt6JTjJRZTjSNr/jvywzQIDSzdLjMmX0mWCmZqPJYcsf0tcY9FtGSo6FhiZ8VXzFT2c5auhVF1v/Ywuy/X0LkoPJbtjFGx0qQvYMTexI/6YnQM99kqx766C8xbgtnwZgnbcsCLWtamh/rJRnHvH+abzavNx1oRbDeaFEVINoI+zsgKRQLwv+1EIXRzQf1iqHLDRVKrGVnHcd4VS0TsYaY 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 Fri, Nov 14 2025, Pasha Tatashin wrote: > Currently, the output FDT is added to debugfs only when KHO is > finalized and removed when aborted. > > There is no need to hide the FDT based on the state. Always expose it > starting from initialization. This aids the transition toward removing > the explicit abort functionality and converting KHO to be fully > stateless. > > Also, pre-zero the FDT tree so we do not expose random bits to the > user and to the next kernel. > > Signed-off-by: Pasha Tatashin > --- > kernel/liveupdate/kexec_handover.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c > index 83aca3b4af15..cd8641725343 100644 > --- a/kernel/liveupdate/kexec_handover.c > +++ b/kernel/liveupdate/kexec_handover.c > @@ -1147,8 +1147,6 @@ int kho_abort(void) > __kho_abort(); > kho_out.finalized = false; > > - kho_debugfs_fdt_remove(&kho_out.dbg, kho_out.fdt); > - > return 0; > } > > @@ -1219,9 +1217,6 @@ int kho_finalize(void) > > kho_out.finalized = true; > > - WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, "fdt", > - kho_out.fdt, true)); > - > return 0; > } > > @@ -1310,7 +1305,7 @@ static __init int kho_init(void) > if (!kho_enable) > return 0; > > - fdt_page = alloc_page(GFP_KERNEL); > + fdt_page = alloc_page(GFP_KERNEL | __GFP_ZERO); If I read the series right, patch 9 will make this a full FDT with no subnodes. That makes a lot more sense than a zero page. Thinking out loud. For this patch, Reviewed-by: Pratyush Yadav > if (!fdt_page) { > err = -ENOMEM; > goto err_free_scratch; > @@ -1344,6 +1339,9 @@ static __init int kho_init(void) > init_cma_reserved_pageblock(pfn_to_page(pfn)); > } > > + WARN_ON_ONCE(kho_debugfs_fdt_add(&kho_out.dbg, "fdt", > + kho_out.fdt, true)); > + > return 0; > > err_free_fdt: -- Regards, Pratyush Yadav