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c=relaxed/simple; d=linux-foundation.org; s=korg; t=1689094354; bh=tPUlfpdEgVeWU0fEHmbznxG/fGtFy4lDdLUuzVWVgqU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Ifj3AekL98UeHTVQ1xETMb3/VKh08B5fL854XmdDUd9ksG2I7VYkY1ZcVn/9Sb/o4 rHd70rHd4B6iP9MbnqQa+A8/Jn/zkdH/rHsGz7ViYLrSxCXhSl4G4alFIgvCeF4YbB 0SCL1lbtyu6s3X2g84bDvTB/gZumLGBIdOMqY1jE= Date: Tue, 11 Jul 2023 09:52:33 -0700 From: Andrew Morton To: Claudio Imbrenda Cc: Matthew Wilcox , Christian Borntraeger , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gerald Schaefer , linux-s390 Subject: Re: [PATCH v5 00/38] New page table range API Message-Id: <20230711095233.aa74320d729c1da818a6a4ed@linux-foundation.org> In-Reply-To: <20230711172440.77504856@p-imbrenda> References: <20230710204339.3554919-1-willy@infradead.org> <8cfc3eef-e387-88e1-1006-2d7d97a09213@linux.ibm.com> <20230711172440.77504856@p-imbrenda> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: niqqi9hm4r9q8x3h7efmd7nxu1ayoxr5 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 440DA100019 X-Rspam-User: X-HE-Tag: 1689094355-382813 X-HE-Meta: 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 sb6Qn9fP jeW06gRaZDob+oGssR5HDc5Ez4vv7L3TY403TkMjICiMAhqovGnbm0Q45yJnucrrJhi5e+BSJ3PSkF6hVxVKsKNehw/Iwhni+Ub973sFVG+IE6AaGX1JCtJQ6ghP9be+Xc6+tqGjMrZvQ/pwJ+bJvcwqjpqmwuqv55joZQ7zNi804LWBvS1UJ37WB2AVMhfeVjIF2Xn9LR+dMi14uTQwcNPZAogeBd6SUKrBJhNvzXtBeeWWIRdYXGtUPvgrpINs8kvb2gL/UQouCq0uGLdIhQj0SKxedTZTAAQN+oKtKD5jAlrZKFLmYBRd5rVjuEeBSFo6VIyyeVc8c3oMVUWhDxo4AoH+AyBE6wggYM0CI6+6sXrzPqYCDTToVIKMuQObwX8M8vSy0+D9lXOsUbpR9kcZ0PHxekOg/RD+y 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 Tue, 11 Jul 2023 17:24:40 +0200 Claudio Imbrenda wrote: > On Tue, 11 Jul 2023 13:36:27 +0100 > Matthew Wilcox wrote: > > > On Tue, Jul 11, 2023 at 11:07:06AM +0200, Christian Borntraeger wrote: > > > Am 10.07.23 um 22:43 schrieb Matthew Wilcox (Oracle): > > > > This patchset changes the API used by the MM to set up page table entries. > > > > The four APIs are: > > > > set_ptes(mm, addr, ptep, pte, nr) > > > > update_mmu_cache_range(vma, addr, ptep, nr) > > > > flush_dcache_folio(folio) > > > > flush_icache_pages(vma, page, nr) > > > > > > > > flush_dcache_folio() isn't technically new, but no architecture > > > > implemented it, so I've done that for them. The old APIs remain around > > > > but are mostly implemented by calling the new interfaces. > > > > > > > > The new APIs are based around setting up N page table entries at once. > > > > The N entries belong to the same PMD, the same folio and the same VMA, > > > > so ptep++ is a legitimate operation, and locking is taken care of for > > > > you. Some architectures can do a better job of it than just a loop, > > > > but I have hesitated to make too deep a change to architectures I don't > > > > understand well. > > > > > > > > One thing I have changed in every architecture is that PG_arch_1 is now a > > > > per-folio bit instead of a per-page bit. This was something that would > > > > have to happen eventually, and it makes sense to do it now rather than > > > > iterate over every page involved in a cache flush and figure out if it > > > > needs to happen. > > > > > > I think we do use PG_arch_1 on s390 for our secure page handling and > > > making this perf folio instead of physical page really seems wrong > > > and it probably breaks this code. > > > > Per-page flags are going away in the next few years, so you're going to > > For each 4k physical page frame, we need to keep track whether it is > secure or not. > > A bit in struct page seems the most logical choice. If that's not > possible anymore, how would you propose we should do? > > > need a new design. s390 seems to do a lot of unusual things. I wish > > s390 is an unusual architecture. we are working on un-weirding our > code, but it takes time > This issue sounds fatal for this version of this patchset?