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[213.151.95.130]) by smtp.gmail.com with ESMTPSA id t1sm2693672wma.43.2019.12.10.02.34.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Dec 2019 02:34:52 -0800 (PST) Date: Tue, 10 Dec 2019 11:34:52 +0100 From: Michal Hocko To: David Hildenbrand Cc: Dan Williams , Logan Gunthorpe , Linux Kernel Mailing List , Linux ARM , linux-ia64@vger.kernel.org, linuxppc-dev , linux-s390 , Linux-sh , platform-driver-x86@vger.kernel.org, Linux MM , Christoph Hellwig , Andrew Morton , Catalin Marinas , Will Deacon , Benjamin Herrenschmidt , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Andy Lutomirski , Peter Zijlstra Subject: Re: [PATCH 5/6] mm, memory_hotplug: Provide argument for the pgprot_t in arch_add_memory() Message-ID: <20191210103452.GF10404@dhcp22.suse.cz> References: <20191209191346.5197-1-logang@deltatee.com> <20191209191346.5197-6-logang@deltatee.com> <20191210100432.GC10404@dhcp22.suse.cz> <6da2b279-6a6d-d89c-a34c-962ed021d91d@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6da2b279-6a6d-d89c-a34c-962ed021d91d@redhat.com> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 10-12-19 11:09:46, David Hildenbrand wrote: > On 10.12.19 11:04, Michal Hocko wrote: > > On Mon 09-12-19 12:43:40, Dan Williams wrote: > >> On Mon, Dec 9, 2019 at 12:24 PM Logan Gunthorpe wrote: > >>> > >>> > >>> > >>> On 2019-12-09 12:23 p.m., David Hildenbrand wrote: > >>>> On 09.12.19 20:13, Logan Gunthorpe wrote: > > [...] > >>>>> #ifdef CONFIG_MEMORY_HOTPLUG > >>>>> -int arch_add_memory(int nid, u64 start, u64 size, > >>>>> +int arch_add_memory(int nid, u64 start, u64 size, pgprot_t prot, > >>>>> struct mhp_restrictions *restrictions) > >>>> > >>>> Can we fiddle that into "struct mhp_restrictions" instead? > >>> > >>> Yes, if that's what people want, it's pretty trivial to do. I chose not > >>> to do it that way because it doesn't get passed down to add_pages() and > >>> it's not really a "restriction". If I don't hear any objections, I will > >>> do that for v2. > >> > >> +1 to storing this information alongside the altmap in that structure. > >> However, I agree struct mhp_restrictions, with the MHP_MEMBLOCK_API > >> flag now gone, has lost all of its "restrictions". How about dropping > >> the 'flags' property and renaming the struct to 'struct > >> mhp_modifiers'? > > > > Hmm, this email somehow didn't end up in my inbox so I have missed it > > before replying. > > > > Well, mhp_modifiers makes some sense and it would reduce the API > > proliferation but how do you expect the prot part to be handled? > > I really do not want people to think about PAGE_KERNEL or which > > protection to use because my experience tells that this will get copied > > without much thinking or simply will break with some odd usecases. > > So how exactly this would be used? > > I was thinking about exactly the same "issue". > > 1. default initialization via a function > > memhp_modifier_default_init(&modified); > > 2. a flag that unlocks the prot field (default:0). Without the flag, it > is ignored. We can keep the current initialization then. > > Other ideas? 3. a prot mask to apply on top of PAGE_KERNEL? Or would that be insufficient/clumsy? -- Michal Hocko SUSE Labs