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 D200D81ACA; Fri, 1 Nov 2024 16:06:07 +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=1730477167; cv=none; b=XcJETzJh0Sdu+w8TY4EuUvgLpJaMD+nPXzQ0b5AGFtRPxUCSAqRfEY9oRo83N/RKvzEasN7Wb56a3+fqGn5gN+SjRtxQxVeBeNTG49iOh/2aA0tgtkz/9EUmNJkRzAwxCEqNp02FfKLJkSdq9ynlaDVQo/9S6tsu4OoY4dp7Uj8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730477167; c=relaxed/simple; bh=4S+pRg+jKAU5U0sHcwkK0/Iq9498uZZRXnJEb+oAdv4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=o1YNSKkTdrk7qdAgQRHbHvEke+DhFytNjR+mi3WC3OxS+gSR94Sjw1zxvBbz1AqGzPzR06hjo5Q2mpumLpMXkccp7w+dW0ZuFNBOJvUCuHvwWl27ybTb0JEOZO5XTRspyV5tY2zSQtE9EWQnnANeJElupYhCP8NGkhLThsuHEig= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=a5zELRtH; 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="a5zELRtH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1221EC4CECD; Fri, 1 Nov 2024 16:05:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730477167; bh=4S+pRg+jKAU5U0sHcwkK0/Iq9498uZZRXnJEb+oAdv4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=a5zELRtHls8OA0jW/I9NJV8QWjJ25s4S0RI4BX4gGobl98QHmHNj6seEnbtduRhhV dWzfY1RwUvQxPDeNU710rOM+ApwCThagAjmbno04oYmX0zqhVOGAm5mDfhDB0vtTiB 6kziyYtZX6/UcfOpGPcDzifMAsm06Y2F0axjmnb77Z7srcZHAN/+LIP+zvLjZB483J HZQcpn8RNgYY0d7THaCXPeyUYT0sBEnJzaA69GeOh/3ytpkGfYfozenx/mZFkHyT1a ayDJfiy+S6FyOWW8a1djQtUWTqcSe1keIn/JarTwH53P4uES4GTM/YBPBCjm/Yw+ru rEhoCg2PP1bpw== Date: Fri, 1 Nov 2024 18:02:03 +0200 From: Mike Rapoport To: Gregory Price Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org, Jonathan.Cameron@huawei.com, dan.j.williams@intel.com, rrichter@amd.com, Terry.Bowman@amd.com, dave.jiang@intel.com, ira.weiny@intel.com, alison.schofield@intel.com, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, rafael@kernel.org, lenb@kernel.org, david@redhat.com, osalvador@suse.de, gregkh@linuxfoundation.org, akpm@linux-foundation.org Subject: Re: [PATCH v5 1/3] memory: implement memory_block_advise/probe_max_size Message-ID: References: <20241101134706.1185-1-gourry@gourry.net> <20241101134706.1185-2-gourry@gourry.net> Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241101134706.1185-2-gourry@gourry.net> On Fri, Nov 01, 2024 at 09:47:03AM -0400, Gregory Price wrote: > Hotplug memory sources may have opinions on what the memblock size > should be - usually for alignment purposes. For example, CXL memory > extents can be 256MB with a matching alignment. If this size/alignment > is smaller than the block size, it can result in stranded capacity. > > Implement memory_block_advise_max_size for use prior to allocator init, > for software to advise the system on the max block size. > > Implement memory_block_probe_max_size for use by arch init code to > calculate the best block size. Use of advice is architecture defined. > > The probe value can never change after first probe. Calls to advise > after probe will return -EBUSY to aid debugging. > > On systems without hotplug, always return -ENODEV and 0 respectively. > > Suggested-by: Ira Weiny > Signed-off-by: Gregory Price > Acked-by: David Hildenbrand Acked-by: Mike Rapoport (Microsoft) > --- > drivers/base/memory.c | 53 ++++++++++++++++++++++++++++++++++++++++++ > include/linux/memory.h | 10 ++++++++ > 2 files changed, 63 insertions(+) > > diff --git a/drivers/base/memory.c b/drivers/base/memory.c > index 67858eeb92ed..835793150b41 100644 > --- a/drivers/base/memory.c > +++ b/drivers/base/memory.c > @@ -110,6 +110,59 @@ static void memory_block_release(struct device *dev) > kfree(mem); > } > > + > +/* Max block size to be set by memory_block_advise_max_size */ > +static unsigned long memory_block_advised_size; > +static bool memory_block_advised_size_queried; > + > +/** > + * memory_block_advise_max_size() - advise memory hotplug on the max suggested > + * block size, usually for alignment. > + * @size: suggestion for maximum block size. must be aligned on power of 2. > + * > + * Early boot software (pre-allocator init) may advise archs on the max block > + * size. This value can only decrease after initialization, as the intent is > + * to identify the largest supported alignment for all sources. > + * > + * Use of this value is arch-defined, as is min/max block size. > + * > + * Return: 0 on success > + * -EINVAL if size is 0 or not pow2 aligned > + * -EBUSY if value has already been probed > + */ > +int __init memory_block_advise_max_size(unsigned long size) > +{ > + if (!size || !is_power_of_2(size)) > + return -EINVAL; > + > + if (memory_block_advised_size_queried) > + return -EBUSY; > + > + if (memory_block_advised_size) { > + memory_block_advised_size = min(memory_block_advised_size, > + size); > + } else { > + memory_block_advised_size = size; > + } > + > + return 0; > +} > + > +/** > + * memory_block_advised_max_size() - query advised max hotplug block size. > + * > + * After the first call, the value can never change. Callers looking for the > + * actual block size should use memory_block_size_bytes. This interface is > + * intended for use by arch-init when initializing the hotplug block size. > + * > + * Return: advised size in bytes, or 0 if never set. > + */ > +unsigned long memory_block_advised_max_size(void) > +{ > + memory_block_advised_size_queried = true; > + return memory_block_advised_size; > +} > + > unsigned long __weak memory_block_size_bytes(void) > { > return MIN_MEMORY_BLOCK_SIZE; > diff --git a/include/linux/memory.h b/include/linux/memory.h > index c0afee5d126e..8202d0efbf46 100644 > --- a/include/linux/memory.h > +++ b/include/linux/memory.h > @@ -149,6 +149,14 @@ static inline int hotplug_memory_notifier(notifier_fn_t fn, int pri) > { > return 0; > } > +static inline int memory_block_advise_max_size(unsigned long size) > +{ > + return -ENODEV; > +} > +static inline unsigned long memory_block_advised_max_size(void) > +{ > + return 0; > +} > #else /* CONFIG_MEMORY_HOTPLUG */ > extern int register_memory_notifier(struct notifier_block *nb); > extern void unregister_memory_notifier(struct notifier_block *nb); > @@ -181,6 +189,8 @@ int walk_dynamic_memory_groups(int nid, walk_memory_groups_func_t func, > void memory_block_add_nid(struct memory_block *mem, int nid, > enum meminit_context context); > #endif /* CONFIG_NUMA */ > +int memory_block_advise_max_size(unsigned long size); > +unsigned long memory_block_advised_max_size(void); > #endif /* CONFIG_MEMORY_HOTPLUG */ > > /* > -- > 2.43.0 > -- Sincerely yours, Mike.