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[2003:cb:c703:e200:8511:ed0f:ac2c:42f7]) by smtp.gmail.com with ESMTPSA id hs32sm611210ejc.180.2022.01.13.00.31.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 Jan 2022 00:31:17 -0800 (PST) Message-ID: <81b7f3e5-2350-0aee-918b-b63980354d96@redhat.com> Date: Thu, 13 Jan 2022 09:31:16 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH v2 2/2] powerpc/fadump: opt out from freeing pages on cma activation failure To: Hari Bathini , akpm@linux-foundation.org, linux-mm@kvack.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org Cc: osalvador@suse.de, mike.kravetz@oracle.com, mahesh@linux.ibm.com, sourabhjain@linux.ibm.com References: <20220112193340.149020-1-hbathini@linux.ibm.com> <20220112193340.149020-3-hbathini@linux.ibm.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20220112193340.149020-3-hbathini@linux.ibm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=CvMlLyHn; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf06.hostedemail.com: domain of david@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=david@redhat.com X-Stat-Signature: 1toyeeribn618e8dwwpor9tbobr7z99a X-Rspamd-Queue-Id: 0074818000B X-Rspamd-Server: rspam12 X-HE-Tag: 1642062680-761562 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 12.01.22 20:33, Hari Bathini wrote: > With commit a4e92ce8e4c8 ("powerpc/fadump: Reservationless firmware > assisted dump"), Linux kernel's Contiguous Memory Allocator (CMA) > based reservation was introduced in fadump. That change was aimed at > using CMA to let applications utilize the memory reserved for fadump > while blocking it from being used for kernel pages. The assumption > was, even if CMA activation fails for whatever reason, the memory > still remains reserved to avoid it from being used for kernel pages. > But commit 072355c1cf2d ("mm/cma: expose all pages to the buddy if > activation of an area fails") breaks this assumption as it started > exposing all pages to buddy allocator on CMA activation failure. > It led to warning messages like below while running crash-utility > on vmcore of a kernel having above two commits: > > crash: seek error: kernel virtual address: > > To fix this problem, opt out from exposing pages to buddy allocator > on CMA activation failure for fadump reserved memory. > > Signed-off-by: Hari Bathini > --- > arch/powerpc/kernel/fadump.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c > index b7ceb041743c..82058b52e34a 100644 > --- a/arch/powerpc/kernel/fadump.c > +++ b/arch/powerpc/kernel/fadump.c > @@ -112,6 +112,12 @@ static int __init fadump_cma_init(void) > return 1; > } > > + /* > + * If CMA activation fails, keep the pages reserved, instead of > + * exposing them to buddy allocator. Same as 'fadump=nocma' case. > + */ > + cma_reserve_pages_on_error(fadump_cma); > + > /* > * So we now have successfully initialized cma area for fadump. > */ Acked-by: David Hildenbrand -- Thanks, David / dhildenb