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(p200300cbc70a4d00b9689e7aaf8badf7.dip0.t-ipconnect.de. [2003:cb:c70a:4d00:b968:9e7a:af8b:adf7]) by smtp.gmail.com with ESMTPSA id t24-20020adfa2d8000000b0033b86b38611sm3796789wra.10.2024.02.13.01.54.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 13 Feb 2024 01:54:54 -0800 (PST) Message-ID: <940939b2-e36c-4d11-b48f-49f633f0c4fa@redhat.com> Date: Tue, 13 Feb 2024 10:54:52 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 03/25] mm: Make pte_next_pfn() a wrapper around pte_advance_pfn() To: Ryan Roberts , Catalin Marinas , Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , Mark Rutland , Kefeng Wang , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , Nicholas Piggin , Christophe Leroy , "Aneesh Kumar K.V" , "Naveen N. Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" References: <20240202080756.1453939-1-ryan.roberts@arm.com> <20240202080756.1453939-4-ryan.roberts@arm.com> <828d2573-b5fe-43b3-b955-944c05bcdb60@redhat.com> <3bc05163-2671-4239-ae5a-b9207fdca459@arm.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <3bc05163-2671-4239-ae5a-b9207fdca459@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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: linux-mm@kvack.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 12.02.24 22:34, Ryan Roberts wrote: > On 12/02/2024 14:29, David Hildenbrand wrote: >> On 12.02.24 15:10, Ryan Roberts wrote: >>> On 12/02/2024 12:14, David Hildenbrand wrote: >>>> On 02.02.24 09:07, Ryan Roberts wrote: >>>>> The goal is to be able to advance a PTE by an arbitrary number of PFNs. >>>>> So introduce a new API that takes a nr param. >>>>> >>>>> We are going to remove pte_next_pfn() and replace it with >>>>> pte_advance_pfn(). As a first step, implement pte_next_pfn() as a >>>>> wrapper around pte_advance_pfn() so that we can incrementally switch the >>>>> architectures over. Once all arches are moved over, we will change all >>>>> the core-mm callers to call pte_advance_pfn() directly and remove the >>>>> wrapper. >>>>> >>>>> Signed-off-by: Ryan Roberts >>>>> --- >>>>>    include/linux/pgtable.h | 8 +++++++- >>>>>    1 file changed, 7 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h >>>>> index 5e7eaf8f2b97..815d92dcb96b 100644 >>>>> --- a/include/linux/pgtable.h >>>>> +++ b/include/linux/pgtable.h >>>>> @@ -214,9 +214,15 @@ static inline int pmd_dirty(pmd_t pmd) >>>>>        #ifndef pte_next_pfn >>>>> +#ifndef pte_advance_pfn >>>>> +static inline pte_t pte_advance_pfn(pte_t pte, unsigned long nr) >>>>> +{ >>>>> +    return __pte(pte_val(pte) + (nr << PFN_PTE_SHIFT)); >>>>> +} >>>>> +#endif >>>>>    static inline pte_t pte_next_pfn(pte_t pte) >>>>>    { >>>>> -    return __pte(pte_val(pte) + (1UL << PFN_PTE_SHIFT)); >>>>> +    return pte_advance_pfn(pte, 1); >>>>>    } >>>>>    #endif >>>>> >>>> >>>> I do wonder if we simply want to leave pte_next_pfn() around? Especially patch >>>> #4, #6 don't really benefit from the change? So are the other set_ptes() >>>> implementations. >>>> >>>> That is, only convert all pte_next_pfn()->pte_advance_pfn(), and leave a >>>> pte_next_pfn() macro in place. >>>> >>>> Any downsides to that? >>> >>> The downside is just having multiple functions that effectively do the same >>> thing. Personally I think its cleaner and easier to understand the code with >>> just one generic function which we pass 1 to it where we only want to advance by >>> 1. In the end, there are only a couple of places where pte_advance_pfn(1) is >>> used, so doesn't really seem valuable to me to maintain a specialization. >> >> Well, not really functions, just a macro. Like we have set_pte_at() translating >> to set_ptes(). >> >> Arguably, we have more callers of set_pte_at(). >> >> "Easier to understand", I don't know. :) >> >>> >>> Unless you feel strongly that we need to keep pte_next_pfn() then I'd prefer to >>> leave it as I've done in this series. >> >> Well, it makes you patch set shorter and there is less code churn. >> >> So personally, I'd just leave pte_next_pfn() in there. But whatever you prefer, >> not the end of the world. > > I thought about this a bit more and remembered that I'm the apprentice so I've > changed it as you suggested. Oh, I say stupid things all the time. Please push back if you disagree. :) [shrinking a patch set if possible and reasonable is often a good idea] -- Cheers, David / dhildenb