From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 30DA9381B6; Tue, 30 Jan 2024 05:51:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706593876; cv=none; b=XtENmQdl9Y2IlUsMdRubQggyKpR9I9yfn7cqE2sWYtI+rbCTJ54ubJ9pugVPnTrY65hhkBCxDqfztf+SSDBgMj3SKdhQl1d63xN+Ewxiar2tjD8CNd1lBzGoOAI+1kxn7PESm7XgQ6XQ4c7pmr+jQ9k9Aw6Zpqi4pkPYqo1z45Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706593876; c=relaxed/simple; bh=8K9UnuvMcRu/4phSXWdkX2JClt3ysuFpTGp94GiiMvo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=tTF6bWCJ5ght04NB6+fL4TUw6mw/tjYIThNu6T+AN/vHyeeCmPTrk1sYuAm3rHa3vUa40inIRJjgRyIjYbRc3yn8zLC7VmC5zatoOLKxRME7C83guQq2fGqCBlyGxTXLCrM0zMyzci4aDxUMmaRBg9as/eZe1M8tQlMLl30hLso= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3B643DA7; Mon, 29 Jan 2024 21:51:57 -0800 (PST) Received: from [10.163.41.110] (unknown [10.163.41.110]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5F9903F762; Mon, 29 Jan 2024 21:51:00 -0800 (PST) Message-ID: <830691cf-cb96-443e-b6eb-2adfe2edd587@arm.com> Date: Tue, 30 Jan 2024 11:20:56 +0530 Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v3 09/35] mm: cma: Introduce cma_remove_mem() Content-Language: en-US To: Alexandru Elisei , catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org, rppt@kernel.org, hughd@google.com Cc: pcc@google.com, steven.price@arm.com, vincenzo.frascino@arm.com, david@redhat.com, eugenis@google.com, kcc@google.com, hyesoo.yu@samsung.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org References: <20240125164256.4147-1-alexandru.elisei@arm.com> <20240125164256.4147-10-alexandru.elisei@arm.com> From: Anshuman Khandual In-Reply-To: <20240125164256.4147-10-alexandru.elisei@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 1/25/24 22:12, Alexandru Elisei wrote: > Memory is added to CMA with cma_declare_contiguous_nid() and > cma_init_reserved_mem(). This memory is then put on the MIGRATE_CMA list in > cma_init_reserved_areas(), where the page allocator can make use of it. cma_declare_contiguous_nid() reserves memory in memblock and marks the for subsequent CMA usage, where as cma_init_reserved_areas() activates these memory areas through init_cma_reserved_pageblock(). Standard page allocator only receives these memory via free_reserved_page() - only if the page block activation fails. > > If a device manages multiple CMA areas, and there's an error when one of > the areas is added to CMA, there is no mechanism for the device to prevent What kind of error ? init_cma_reserved_pageblock() fails ? But that will not happen until cma_init_reserved_areas(). > the rest of the areas, which were added before the error occured, from > being later added to the MIGRATE_CMA list. Why is this mechanism required ? cma_init_reserved_areas() scans over all CMA areas and try and activate each of them sequentially. Why is not this sufficient ? > > Add cma_remove_mem() which allows a previously reserved CMA area to be > removed and thus it cannot be used by the page allocator. Successfully activated CMA areas do not get used by the buddy allocator. > > Signed-off-by: Alexandru Elisei > --- > > Changes since rfc v2: > > * New patch. > > include/linux/cma.h | 1 + > mm/cma.c | 30 +++++++++++++++++++++++++++++- > 2 files changed, 30 insertions(+), 1 deletion(-) > > diff --git a/include/linux/cma.h b/include/linux/cma.h > index e32559da6942..787cbec1702e 100644 > --- a/include/linux/cma.h > +++ b/include/linux/cma.h > @@ -48,6 +48,7 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size, > unsigned int order_per_bit, > const char *name, > struct cma **res_cma); > +extern void cma_remove_mem(struct cma **res_cma); > extern struct page *cma_alloc(struct cma *cma, unsigned long count, unsigned int align, > bool no_warn); > extern int cma_alloc_range(struct cma *cma, unsigned long start, unsigned long count, > diff --git a/mm/cma.c b/mm/cma.c > index 4a0f68b9443b..2881bab12b01 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -147,8 +147,12 @@ static int __init cma_init_reserved_areas(void) > { > int i; > > - for (i = 0; i < cma_area_count; i++) > + for (i = 0; i < cma_area_count; i++) { > + /* Region was removed. */ > + if (!cma_areas[i].count) > + continue; Skip previously added CMA area (now zeroed out) ? > cma_activate_area(&cma_areas[i]); > + } > > return 0; > } cma_init_reserved_areas() gets called via core_initcall(). Some how platform/device needs to call cma_remove_mem() before core_initcall() gets called ? This might be time sensitive. > @@ -216,6 +220,30 @@ int __init cma_init_reserved_mem(phys_addr_t base, phys_addr_t size, > return 0; > } > > +/** > + * cma_remove_mem() - remove cma area > + * @res_cma: Pointer to the cma region. > + * > + * This function removes a cma region created with cma_init_reserved_mem(). The > + * ->count is set to 0. > + */ > +void __init cma_remove_mem(struct cma **res_cma) > +{ > + struct cma *cma; > + > + if (WARN_ON_ONCE(!res_cma || !(*res_cma))) > + return; > + > + cma = *res_cma; > + if (WARN_ON_ONCE(!cma->count)) > + return; > + > + totalcma_pages -= cma->count; > + cma->count = 0; > + > + *res_cma = NULL; > +} > + > /** > * cma_declare_contiguous_nid() - reserve custom contiguous area > * @base: Base address of the reserved area optional, use 0 for any But first please do explain what are the errors device or platform might see on a previously marked CMA area so that removing them on way becomes necessary preventing their activation via cma_init_reserved_areas().