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[35.245.167.64]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5ee3243e30fsm81430e0c.9.2026.11.12.07.00.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Nov 2026 07:00:35 -0800 (PST) X-Archived-By: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Thu, 12 Nov 2026 10:00:34 -0500 Message-Id: Cc: "Alexander Graf" , "Andrew Morton" , "Chen Pei" , "George Guo" , "Kexin Liu" , "Randy Dunlap" , "Shuah Khan" , "Sourabh Jain" , , , , Subject: Re: [PATCH v3 5/5] kho: docs: update description of bootmem regions From: "Pasha Tatashin" To: "Mike Rapoport (Microsoft)" , "Jonathan Corbet" , "Pasha Tatashin" , "Pratyush Yadav" X-Mailer: aerc 0.22.0-39-g5d7784875be2 References: <20261112-kho-bootmem-sizing-v3-0-f0c8d00295d5@kernel.org> <20261112-kho-bootmem-sizing-v3-5-f0c8d00295d5@kernel.org> In-Reply-To: <20261112-kho-bootmem-sizing-v3-5-f0c8d00295d5@kernel.org> X-Stat-Signature: oaq9tm51bgdert5fpoeb18zw7byshtyd X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 1565480011 X-HE-Tag: 1794495636-605392 X-HE-Meta: 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 IwiM5+Al ZANWq6ATR9vIBTxIpeDHjJAYXXI9oVGzAl/B4mjzlJBMcxHt6WNFy71f02PbFCewg67L7nuXZXoPwP68BxBTCRlluJhc5XB2K3hGvFozH8/zrwGBRNnzl8rMWV8N9HCEHkacjLqxhKakD4f8B7BJ6enE7GNNTpWZn3BbyU8kA91m45a/k8TVTJUOR41AIQ7SiAHYvq8w6Lico8yTkouFld5MSd5T9wFHbn9VthJ9lIR36LGG92VybqWm+Lsy9GFtscpGaSrJOn8AonUC4QA+nFK48xjIwbdLRxzrrJe3G7zt9lGrm+PsK7SOHPvAS4MGy9wEqtdCz+tMrLd8yAhFrkrMmo+bLWXEjI6pZhq+hW/MiVKUZPx2SJ52QgrcccMmMBpjgVheI2TX0nlmPN284O+h5uDZjHULHF9WA5cwwea/fTzx5cjuOfOWD2g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Thu Nov 12, 2026 at 5:38 AM EST, Mike Rapoport (Microsoft) wrote: > The description of the boot memory regions does not mention the low > memory region and claims there is always a region per node plus a global > region, while the low memory and the global regions are not allocated > when they would be empty. > > List all types of the boot memory regions and describe when they are not > allocated. > > While on it, fix grammar and split the description of the regions size > and of the CMA usage into separate paragraphs. > > Signed-off-by: Mike Rapoport (Microsoft) > --- > Documentation/core-api/kho/index.rst | 31 ++++++++++++++++++++----------= - > 1 file changed, 20 insertions(+), 11 deletions(-) > > diff --git a/Documentation/core-api/kho/index.rst b/Documentation/core-ap= i/kho/index.rst > index e78a2bbe2be1d..ce2bf9cf66514 100644 > --- a/Documentation/core-api/kho/index.rst > +++ b/Documentation/core-api/kho/index.rst > @@ -52,17 +52,26 @@ allocations before during boot up to the initializati= on of the page allocator. > =20 > We guarantee that we always have such regions through the boot memory re= gions: > On first boot KHO allocates several physically contiguous memory regions= . Since > -after kexec these regions will be used by early memory allocations, ther= e is a > -boot memory region per NUMA node plus a boot memory region to satisfy > -allocations requests that do not require particular NUMA node assignment= . By > -default, size of the boot memory region is calculated based on amount of= memory > -allocated during boot. The ``kho_bootmem`` kernel command line option ma= y be > -used to explicitly define size of the boot memory regions. The boot memo= ry > -regions are declared as CMA when page allocator is initialized so that t= heir > -memory can be used during system lifetime. CMA gives us the guarantee th= at no > -handover pages land in that region, because handover pages must be at a = static > -physical memory location and CMA enforces that only movable pages can be= located > -inside. > +after kexec these regions will be used by early memory allocations, ther= e are > +several types of such regions to ensure that all boot-time allocations w= ork: > + > +* a low memory region for allocations below ``ARCH_LOW_ADDRESS_LIMIT`` > +* a region per NUMA node > +* a global region for allocations that do not require a particular NUMA = node > + > +Regions that would be empty are not allocated. For example, there is no = low > +memory region when ``ARCH_LOW_ADDRESS_LIMIT`` covers all memory, and the= re is > +no global region when ``CONFIG_NUMA`` is disabled. > + > +By default, the size of the boot memory regions is calculated based on t= he > +amount of memory allocated during boot. The ``kho_bootmem`` kernel comma= nd line > +option may be used to explicitly define the size of the boot memory regi= ons. > + > +The boot memory regions are declared as CMA when the page allocator is > +initialized so that their memory can be used during system lifetime. CMA= gives > +us the guarantee that no handover pages land in that region, because han= dover > +pages must be at a static physical memory location and CMA enforces that= only > +movable pages can be located inside. > =20 > After KHO kexec, we ignore the ``kho_bootmem`` kernel command line optio= n and > instead reuse the exact same region that was originally allocated. This = allows Reviewed-by: Pasha Tatashin =20 --=20 Pasha