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b=lZX7OAEO4iV5S1+YXwOnpNeXysrLeSryC2YE5VkGmWFuQ1wIf+WHQIRsPfY64kEvv QzcQMAowqKlFIJSrHE1eEuBK6vW1P1AekwkoCcjrd4HOlzlC6jenE3ECVGpLYdDivk qyjpj02i46dkWEnCNEDjQSNs/9x6Jd21DB4k9HTMhz5nsiU0DfPOYMHteLZ1wJLASP qpUPUOOVkMdmZ1Z9ow7qaMytrTTWQK6SBmBQ51D/RRDYYx10iAwqrguOIiiU8j9v8N 4iS480IBHW3v/cY6/gPBGGopu5lpSm9aIIhXlxXD27EoChcg/w8dp4NObDJYFg5pZk akcmTCNvjNGFA== From: Pratyush Yadav To: Mike Rapoport Cc: Andrew Morton , Alexander Graf , Baoquan He , Changyuan Lyu , Pasha Tatashin , Pratyush Yadav , Shuah Khan , Thomas Weischuh , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/3] kho: allow scratch areas with zero size In-Reply-To: <20250811082510.4154080-2-rppt@kernel.org> References: <20250811082510.4154080-1-rppt@kernel.org> <20250811082510.4154080-2-rppt@kernel.org> Date: Wed, 13 Aug 2025 15:45:29 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DC8CA100006 X-Stat-Signature: gjc6is3regnzfa6b7xucnuistwefssnx X-Rspam-User: X-HE-Tag: 1755092732-549397 X-HE-Meta: U2FsdGVkX1/l+gWg7xjljCsa5r1gkaOrpivxr6eT99vyp+gblE8IMBu0fxXhzpWcRou5+SAhQSJ6ucqF4Repr85kjBfpt6ZBfwEUrJl5Wsb2dFrxgm7SkbWfBYHFeUmJsiDFiWxjj32c+s17h4SPtePy0HMVHGIA5zDxJjlyeLzdNkEDaAfXyqEO+x1SFE/Pthqh4eZaZ/isX1zJqS9CSOgV2pxTQ+dl8QXNLMrkmMKeFm6yUXirwpEK2HmwkHMs/VH0s+2PfywII+TOEx6wRwnW3tWSMyOt/+awDQvRQDXJ9c+2kaHKvI7swOWSXvStrLiZ+fydPi58Ms7eexu1sU/Or732i3qa00USZnV/MOYCLZ239pkiK4APwiCe0aLCG1wIfgLQkAxv6/QsUpGCGpHycftQ4IVbmPgz3ZrsY7wUmF4xp4DB3LLI3LmwK6og0jXgASwKdbvVdfTxtp2JKb/BiAJFmEwzvKtcbhbhSBtbYqA2dtb5M6Bjn/fthTOOl9AAAPUxo1GqiGPNR28kRWvmfNZSzbgMNrFimWjA+IC0m2hbJloDP5EWJc/cFuYy0jny9uuAmf+LPY/pflJ2yM1kjd5hTK/UaipzBW6scW0XVYOKw59GPi4kQUm6p1q5ms4/DBwTC31LeyCo6H8JijeSVNcNZpiGlBRZEzz8NaVa2d6oPFMxjaW7fV299oi4BGeGEHT0hqStAL5irFECreHkyPYTU2EjnjTninksSlvAntFSWj6X+3Cmyji966g4y2JlV+ZvgYD3hdiH3tMOI5JidjYqKwXWiPvr+WQVQeHfMp3VRduLY+UmnJIDZc1hV3lG2z3q7ciBA9cNnKDYXvjFYQk7swwxk5+BglwlsthDgW7qsDamq1iEQV1m3Dp/25vH6VFYYBTx6nc2RIqyXKh5MC/IPpf3MrhulcNaYcqN2+qMVXZ/B7vM6XsxllvhEIlH+ftPMB9FQv1ANAh 31kk6E5r DStCN8RLUxBUBUwgYs62zjgNBgA4Nokf7SSizT4D/Lu+wpNTaTMd0ItH6/RfZzphqN8NIAPREza5nApkzhtl1FdM+1MROOO6zyWgFZ5vVxQuscBiiRi7Syp/caMbzfcK9pl3Y51xWnf7zSDY+p6qIQ/Ex7gTpVwFtsH/u 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, Aug 11 2025, Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" > > Parsing of kho_scratch parameter treats zero size as an invalid value, > although it should be fine for user to request zero sized scratch area > for some types if scratch memory, when for example there is no need to > create scratch area in the low memory. Can the system boot with 0 per-node memory? If not, then perhaps we should only allow lowmem scratch to be zero? > > Treat zero as a valid value for a scratch area size but reject > kho_scratch parameter that defines no scratch memory at all. > > Signed-off-by: Mike Rapoport (Microsoft) > --- > kernel/kexec_handover.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c > index e49743ae52c5..c6ac5a5e51cb 100644 > --- a/kernel/kexec_handover.c > +++ b/kernel/kexec_handover.c > @@ -385,6 +385,7 @@ static int __init kho_parse_scratch_size(char *p) > { > size_t len; > unsigned long sizes[3]; > + size_t total_size = 0; > int i; > > if (!p) > @@ -421,11 +422,15 @@ static int __init kho_parse_scratch_size(char *p) > } > > sizes[i] = memparse(p, &endp); > - if (!sizes[i] || endp == p) > + if (endp == p) > return -EINVAL; > p = endp; > + total_size += sizes[i]; > } > > + if (!total_size) > + return -EINVAL; > + Looks good. BTW, unrelated to this patch, but should we also check that p == '\0' here to make sure the whole argument was consumed? > scratch_size_lowmem = sizes[0]; > scratch_size_global = sizes[1]; > scratch_size_pernode = sizes[2]; -- Regards, Pratyush Yadav