From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=209.85.221.176 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794495637; b=Hw3ZyZBs4kLTRx4rkO+kdebZ7M1hluGmLkbKfnaYAePqBjInCp42Pkr7YmT6ilhJ7Zzy dSjmsCCrjXBFD3KD+8OeVjMCHZXJD6cN5TbHhP+FPmjB3IuW1wl91kwXqpXNU3yT/BgjR v3j14bnJR1zpbfY0gv0yPZ1eZbyZF6pZomvBJkJR9VtkAezXB75W1WyejuUmwGwPUeH7o QJmZD6MFSwx8yMI88ojAQg32v6oDmRt6RxUSPxmTq3+ob6U4L9fcN6lB5X4qpAsvPtIIy RcZHFlo7nVYXWci08LkKRt9MAj/B1HOwA/gcnL3GO9zSrAw6YhlHJMfN/4TBUfhE1RA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794495637; h=DMARC-Filter:Received:DKIM-Signature:X-Google-DKIM-Signature: X-Forwarded-Encrypted:X-Gm-Message-State:X-Gm-Gg:X-Received:Received: Mime-Version:Content-Transfer-Encoding:Content-Type:Date:Message-Id: Cc:Subject:From:To:X-Mailer:References:In-Reply-To; bh=8yYqy1tuA0FyJjrVSCVgV+Doj8Jl7Ml/5bTTP3YOpXU=; b=kEVKbXzg0+cAyIGNc0pHs5YyQxM5KXQvUd+j8WX0cS/tIkB8LxClxP6k08h8GqWrVgk8 4r0snjsQbedT5T4I6Dwd2cN4Y8Fm4L9ZuhZQC0F5URRw6oFVrUtXumVKgsLGxyATCcYOo 2cuNd2ZHZFOy7J1hMeOk3fA3QUTS08rqyOqRU4E6oPa380oghxUEqvS/AyZDPZsGn/QdT JOzh5KWom6YnPp+SZ9CsouzjOGmv2JugNDKkWvDVca9nbP2LeM/4XHNJYUTDMLLpQTk9B +MC3QHj+xOPPW7M+R2Xztdk7peYwHnbx9CLUKiRDrBFELxCyYVEv88Z5qLpIBC3K3zw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=soleen.com; spf=pass smtp.mailfrom=soleen.com; dkim=pass header.d=soleen.com header.i=@soleen.com header.a=rsa-sha256 header.s=google header.b=UNTUk5Ph; arc=none smtp.remote-ip=209.85.221.176 Received: from mail-vk1-f176.google.com (mail-vk1-f176.google.com [209.85.221.176]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 14C6E606A31C for ; Thu, 12 Nov 2026 15:00:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 14C6E606A31C Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=soleen.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=soleen.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=soleen.com header.i=@soleen.com header.a=rsa-sha256 header.s=google header.b=UNTUk5Ph Received: by mail-vk1-f176.google.com with SMTP id 71dfb90a1353d-5ee2ad94713so433375e0c.0 for ; Thu, 12 Nov 2026 07:00:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=soleen.com; s=google; t=1794495636; x=1795100436; darn=vger.kernel.org; h=in-reply-to:references:to:from:subject:cc:message-id:date :content-type:content-transfer-encoding:mime-version:from:to:cc :subject:date:message-id:reply-to:content-type; bh=8yYqy1tuA0FyJjrVSCVgV+Doj8Jl7Ml/5bTTP3YOpXU=; b=UNTUk5Phl6735h5yGynAgTS/6C2cJAMQ5iWpSsj5LGh9dtu6ZbUQ28l9PCUZyDWFS2 984cM+oMihbSSW0raUu6jnUzRcE4QjotUXIJukljUMS2LAKKCPb0itQ7GlX5XUb4E/Yk SKuDu87H7pV4G1oTWB77pRyK19GkF9y0JTc2S4ofIz0Os8H+TLP9NJthH1O5IJX5AOL5 naVwG5XJzQSxQgYOJ2lKVnivL3+dtVsuXDcE1TqT4jw+WXUDMC3oSYgSdJYXWwcDBDg5 l0vhl/Ozl5n2wi4MF0827C8dfNJtX6U5VONtrUegzVnq2Lt0hBh42Q5KGK56Et30gRE6 3xZQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1794495636; x=1795100436; h=in-reply-to:references:to:from:subject:cc:message-id:date :content-type:content-transfer-encoding:mime-version:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=8yYqy1tuA0FyJjrVSCVgV+Doj8Jl7Ml/5bTTP3YOpXU=; b=EPkuFghEHvIpbNth89khpTy+rj4okxIJFUNHhv4Ud5xaiSDMNhOJ/sg/ybwBgZ37fm Ylk9yrH98CNzyk4DLgt3Q3/yatSuQcjrf0giCQwQLMzZCy5+H+g8/6i1L7NlhED0aznU BIRn7Maj5wa1/OxcNWI8I+hwt7H/KBaXv6Prkc1WcXbtc5e95y76UYhaD9YBvZt4NK0U kTbNoIUFd2bEsgjifpllQxXfMuZGGLEn3AnomPmNof6vNyefgn35D0SOMCF1TKAfZV1i WCfGTTnbW4Qt2vktAIIra3bc/7KO0pqKfYDhZyTjOl3lCMhg06cJZmyTKdcYP3sxx3K8 xsZg== X-Forwarded-Encrypted: i=1; AL+hErFGe93iRl8ZylWs7+QHNNP3idhPpquZ30EuRaiwLt+JIIh8p0zn4GKAIdAeS86pclnMYI5f7ZBnTgLdkC4=@vger.kernel.org X-Gm-Message-State: APuU4Z9y9vPEkR1PfTS5oLZ/L2WvpSXnzcjfXumrREy+2v/jeewkgqwW 6jhP3BvgkL+FtbH1qcG4Skc9neWzF/AJpNKHs3OfIoS5ex7XBcEosxKpC0yDBq+fmSc= X-Gm-Gg: AYBFou3J8KNlGWj7HkyH91R5gT1vPus5fnOL16jbHWAw0ZRMeo8+VQyaxFaHxhBm+fJ fLsF1Q70YBRC81p7AR+BBm5dlu0eRNhCFO8kCPfTWp/2tNyJdnexEpUo8b7w6wDC4r6on8GAFTn UCBQkpMbtfPemqvN1gc/bgpwu79DTOVzsUhumH6o7Z7GGKqsvZKrzx9rX99KbYNaCgsQxC1TvWd IRiXwdKJ5CsRj6H4pjgmnjQX6LMXUoqoBkaQJYMzA2I8k23ClBY4qYZ0CD1+MM64wzgwYqPOZAy z/3ADNaV+RjbNRdljv5EEcnPJFefhc//jZvXaHxN5N+s93xttL6Dy23YkipQO6ri4GWFwPyQ3DM rYQOkFsbdGUQyuD/Xnu9tuS8EpnY9Hn82niYwRQug2K113bydq5lc7/w5JWjc57vwT49MUjSQOQ K9+VQUjlVLoRk1efc9qgypjNNW+2PEZaeNpPEbFesf9EsMUnNalFcCSCtyxeAcW/Soms8E2orqT OTI/Kpla2m5Yd+Qpgb3CXI/nYDXGUzeyJBJfNSxlBgrVSrnhcNqG2oTDFRTk+vfbqC+Sgqeq5XT gBsMigAxoTxFd6eDu0FALSbfPPX6650uhawq8S9VJ8qsaRZIvq6sa5PnGjWUy0s8ZYIZSvPmxzw wLLmezvPqJnSQ98aGtfCxphlYb4mW/o8= X-Received: by 2002:a05:6122:1782:b0:5c9:a7af:8178 with SMTP id 71dfb90a1353d-5ee1c2b2435mr2759606e0c.2.1794495636101; Thu, 12 Nov 2026 07:00:36 -0800 (PST) Received: from localhost (64.167.245.35.bc.googleusercontent.com. [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-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 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> 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