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h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=ErExK45KAh3taU5Ay7lJ7MJ0BMkjWDiD1DN0JR/zuy5xUd2msBop/vOSselq0P951 xqaTacLr4JhC6juOA4x7iB/ICnUr91Z6DOwtkW7YEBLK8BOn6VMNdPLf6s/gJAyqDf wz9mpbOVw45GKbGKmjoqBkjluU1Kbvsvyb6kJTUtCyZcPX8JRc1HxQl06bXJNhzkER ce9WafJQZ8HSp7R53BwGs/NZ53f2B42giPZrrJllQc+T8yfZx9Ko5Zwzg2Alnu/cJR Grg83L4s85KTn/NZGLzo8tA2ilXtoRL7JIw9wePMzXiMSqBRw8ZumQmP0uYiEH8+oT jgB7rSEXyuNog== From: Pratyush Yadav To: Mike Rapoport Cc: Pratyush Yadav , Andrew Morton , Alexander Graf , Baoquan He , Changyuan Lyu , Pasha Tatashin , 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: References: <20250811082510.4154080-1-rppt@kernel.org> <20250811082510.4154080-2-rppt@kernel.org> Date: Wed, 13 Aug 2025 16:25:34 +0200 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A5DC5180012 X-Stat-Signature: 815sxmkq1wb3di8ukoy99ajyrqdw3sxp X-Rspam-User: X-HE-Tag: 1755095138-346617 X-HE-Meta: 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 nSSJxyI0 Vxarw9sMC+O+09ldg9Uod2+FHU1oW+ysB/X0cFjVQgs6sKOjggF0vvGnGXmf1blQiJGeWdYCUpuSg5edd2vV4BQkyLCrH0gBcCB1l3ip/vHpmWn7wVmi0hdgbh2tNPwAI0Z4Tds/MyqZ/erWpnDpUX1Tdqkj8/kxUolUJ 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 Wed, Aug 13 2025, Mike Rapoport wrote: > On Wed, Aug 13, 2025 at 03:45:29PM +0200, Pratyush Yadav wrote: >> 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? > > In most cases yes because most of boot time allocations have fallback to > "any node". > And there's also an option to omit the "global" scratch and boot with only > per-node scratch areas, so I'd keep the possibility of setting any of these > to 0. Makes sense. In that case, Reviewed-by: Pratyush Yadav > >> > 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? > > Care to send a patch? ;-) Will do :-) > >> > scratch_size_lowmem = sizes[0]; >> > scratch_size_global = sizes[1]; >> > scratch_size_pernode = sizes[2]; >> >> -- >> Regards, >> Pratyush Yadav -- Regards, Pratyush Yadav