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Thu, 05 Nov 2026 03:56:26 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fea181085sm9708651f8f.1.2026.11.05.03.56.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Nov 2026 03:56:26 -0800 (PST) Message-ID: Date: Thu, 5 Nov 2026 12:56:24 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] memblock: don't allocate new reserve_mem regions on a KHO boot To: Mike Rapoport Cc: Andrew Morton , Kees Cook , Changyuan Lyu , Alexander Graf , Tony Luck , "Guilherme G. Piccoli" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Pratyush Yadav , Pasha Tatashin , kexec@lists.infradead.org References: <20261104204235.9066-1-azpijr@gmail.com> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/5/26 8:59 AM, Mike Rapoport wrote: > On Wed, Nov 04, 2026 at 09:42:17PM +0100, Jose A. Perez de Azpillaga wrote: >> On a KHO boot, a reserve_mem region that can't be revived is allocated >> from KHO_NOPRSRV memory, which includes the bootmem the next kernel >> boots out of. With CONFIG_KEXEC_HANDOVER_DEBUG, preserving the region >> then fails: >> >> WARNING: kernel/liveupdate/kexec_handover.c:1245 at kho_preserve_pages+0x168/0x180 >> failed to prepare memblock FDT for KHO: -22 >> >> Without it, the next kernel puts its memmap on top of the region and >> the ramoops records in it are lost. >> >> There is no use case for adding regions across a live update, so fail >> instead of allocating, and drop the TODO. >> >> Fixes: f99230780211 ("memblock: add KHO support for reserve_mem") >> Signed-off-by: Jose A. Perez de Azpillaga >> --- >> Changes in v2: >> - fail on a KHO boot instead of allocating outside bootmem, as agreed >> with Pratyush [1]. this drops v1's patch 1. >> - not an RFC anymore. >> - based on v7.4-rc1. >> >> v1: https://lore.kernel.org/all/20261021211058.83483-3-azpijr@gmail.com/ >> >> [1] https://lore.kernel.org/all/2vxzfqxglrg6.fsf@kernel.org/ >> >> mm/memblock.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/mm/memblock.c b/mm/memblock.c >> index a450092a80fb..e325e0542c9a 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -2827,7 +2827,16 @@ static int __init reserve_mem(char *p) >> if (reserve_mem_kho_revive(name, size, align)) >> return 1; >> >> - /* TODO: Allocation must be outside of KHO_NOPRSRV region */ >> + /* >> + * On a KHO boot memblock only allocates from KHO_NOPRSRV memory here, >> + * which includes the bootmem the next kernel boots out of. Only regions >> + * handed over by the previous kernel are supported. >> + */ >> + if (is_kho_boot()) { > > This breaks memblock tests, please add a stub there. oops, sorry. will add it in v3 :) -- cheers, jose a. p-a