From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9DA5B2ED159; Wed, 13 Aug 2025 14:25:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755095137; cv=none; b=sVgCipSDEfkFrUrn4kKX1Il3taEpgOnQ7rYD5H8fvIf9Y8m7jB9wonPFqJxy8xjenYKnrACvV+dEgXHjw/lUgNgnSDxF0AIRW+tAcHMNGmiIagY3J2ebElo5A41fzI96vEW96pOf6dvw2UZGF5X+eZQKSNMBhMYGN+ge+/ditrk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755095137; c=relaxed/simple; bh=s9+rxMFL44IKToOutqxDtZw5jz/ESi8pUno0QbbD/hc=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=XYEoXIf0ecHNL4BK7DA/Lrsp9ieUBbjzKUaO5eQ88SrInZUZNyi009s8w5je6w8ATSRZziKm+oXn64I20sX5qA8DNtNEiRXm7JGp2pz6BHeixXQc1TEj6umNIL1d5MMtdEVf6LbAxSTDIbTBmlNlob3SwfrbR9NfE7mc0cEQIlM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ErExK45K; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="ErExK45K" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E096C4CEF6; Wed, 13 Aug 2025 14:25:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755095137; bh=s9+rxMFL44IKToOutqxDtZw5jz/ESi8pUno0QbbD/hc=; 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) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain 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