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Thu, 29 Oct 2020 18:54:33 +1100 (AEDT) Received: from kernel.org (unknown [87.70.96.83]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id E3F1620EDD; Thu, 29 Oct 2020 07:54:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603958070; bh=5V9raRTAO8xn/TWxASurP3gs711BOhAaxxP12fBIpug=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=smkJOo6ejvJldTmaaqqEFjGX6LWRb76WicHCvCBcrN9qOMMNByoTCZCyPYd8JouA6 FsHRDDeFim9xIzvbeq0FyT0w7eXPAkBTo6qZkKSqULTgH8mtDPy6sKAI1NlM6RXbk0 gkAxCVUoVSgKd/P/vRphpHr37cKvq2I6Usohfbtc= Date: Thu, 29 Oct 2020 09:54:16 +0200 From: Mike Rapoport To: "Edgecombe, Rick P" Subject: Re: [PATCH 2/4] PM: hibernate: improve robustness of mapping pages in the direct map Message-ID: <20201029075416.GJ1428094@kernel.org> References: <20201025101555.3057-1-rppt@kernel.org> <20201025101555.3057-3-rppt@kernel.org> <3b4b2b3559bd3dc68adcddf99415bae57152cb6b.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3b4b2b3559bd3dc68adcddf99415bae57152cb6b.camel@intel.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "david@redhat.com" , "peterz@infradead.org" , "catalin.marinas@arm.com" , "dave.hansen@linux.intel.com" , "linux-mm@kvack.org" , "paulus@samba.org" , "pavel@ucw.cz" , "hpa@zytor.com" , "sparclinux@vger.kernel.org" , "cl@linux.com" , "will@kernel.org" , "linux-riscv@lists.infradead.org" , "linux-s390@vger.kernel.org" , "x86@kernel.org" , "rppt@linux.ibm.com" , "borntraeger@de.ibm.com" , "mingo@redhat.com" , "rientjes@google.com" , "Brown, Len" , "aou@eecs.berkeley.edu" , "gor@linux.ibm.com" , "linux-pm@vger.kernel.org" , "hca@linux.ibm.com" , "bp@alien8.de" , "luto@kernel.org" , "paul.walmsley@sifive.com" , "kirill@shutemov.name" , "tglx@linutronix.de" , "akpm@linux-foundation.org" , "linux-arm-kernel@lists.infradead.org" , "rjw@rjwysocki.net" , "linux-kernel@vger.kernel.org" , "penberg@kernel.org" , "palmer@dabbelt.com" , "iamjoonsoo.kim@lge.com" , "linuxppc-dev@lists.ozlabs.org" , "davem@davemloft.net" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, Oct 28, 2020 at 09:15:38PM +0000, Edgecombe, Rick P wrote: > On Sun, 2020-10-25 at 12:15 +0200, Mike Rapoport wrote: > > + if (IS_ENABLED(CONFIG_ARCH_HAS_SET_DIRECT_MAP)) { > > + unsigned long addr = (unsigned > > long)page_address(page); > > + int ret; > > + > > + if (enable) > > + ret = set_direct_map_default_noflush(page); > > + else > > + ret = set_direct_map_invalid_noflush(page); > > + > > + if (WARN_ON(ret)) > > + return; > > + > > + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > > + } else { > > + debug_pagealloc_map_pages(page, 1, enable); > > + } > > Looking at the arm side again, I think this might actually introduce a > regression for the arm/hibernate/DEBUG_PAGEALLOC combo. > > Unlike __kernel_map_pages(), it looks like arm's cpa will always bail > in the set_direct_map_() functions if rodata_full is false. > > So if rodata_full was disabled but debug page alloc is on, then this > would now skip remapping the pages. I guess the significance depends > on whether hibernate could actually try to save any DEBUG_PAGEALLOC > unmapped pages. Looks like it to me though. __kernel_map_pages() on arm64 will also bail out if rodata_full is false: void __kernel_map_pages(struct page *page, int numpages, int enable) { if (!debug_pagealloc_enabled() && !rodata_full) return; set_memory_valid((unsigned long)page_address(page), numpages, enable); } So using set_direct_map() to map back pages removed from the direct map with __kernel_map_pages() seems safe to me. -- Sincerely yours, Mike.