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[213.175.37.12]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42e754c7580sm148022545e9.47.2024.09.24.00.39.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 24 Sep 2024 00:39:50 -0700 (PDT) Message-ID: Date: Tue, 24 Sep 2024 09:39:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: Move set_pxd_safe() helpers from generic to platform To: Anshuman Khandual , linux-mm@kvack.org, akpm@linux-foundation.org Cc: Paul Walmsley , Palmer Dabbelt , Thomas Gleixner , Dave Hansen , Ryan Roberts , x86@kernel.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org References: <20240920053017.2514920-1-anshuman.khandual@arm.com> <4aad893a-f8ba-4b2e-bded-b01a35ec0a94@redhat.com> <6f178f3c-40fd-45f6-a380-a218429852ca@arm.com> <0245d69d-8544-4068-9739-2d999c1fc599@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: <0245d69d-8544-4068-9739-2d999c1fc599@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; 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Otherwise they just >>>> unnecessarily make the common API more complicated. This moves the helpers >>>> from common code to platform instead. >>>> >>>> Cc: Paul Walmsley >>>> Cc: Palmer Dabbelt >>>> Cc: Thomas Gleixner >>>> Cc: Dave Hansen >>>> Cc: David Hildenbrand >>>> Cc: Ryan Roberts >>>> Cc: Andrew Morton >>>> Cc: x86@kernel.org >>>> Cc: linux-mm@kvack.org >>>> Cc: linux-riscv@lists.infradead.org >>>> Cc: linux-kernel@vger.kernel.org >>>> Suggested-by: David Hildenbrand >>>> Signed-off-by: Anshuman Khandual >>>> --- >>>>   arch/riscv/include/asm/pgtable.h | 19 ++++++++++++++++ >>>>   arch/x86/include/asm/pgtable.h   | 37 +++++++++++++++++++++++++++++++ >>>>   include/linux/pgtable.h          | 38 -------------------------------- >>>>   3 files changed, 56 insertions(+), 38 deletions(-) >>>> >>>> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h >>>> index 089f3c9f56a3..39ca652c5ebe 100644 >>>> --- a/arch/riscv/include/asm/pgtable.h >>>> +++ b/arch/riscv/include/asm/pgtable.h >>>> @@ -957,6 +957,25 @@ void misc_mem_init(void); >>>>   extern unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]; >>>>   #define ZERO_PAGE(vaddr) (virt_to_page(empty_zero_page)) >>>>   +/* >>>> + * Use set_p*_safe(), and elide TLB flushing, when confident that *no* >>>> + * TLB flush will be required as a result of the "set". For example, use >>>> + * in scenarios where it is known ahead of time that the routine is >>>> + * setting non-present entries, or re-setting an existing entry to the >>>> + * same value. Otherwise, use the typical "set" helpers and flush the >>>> + * TLB. >>>> + */ >>>> +#define set_p4d_safe(p4dp, p4d) \ >>>> +({ \ >>>> +    WARN_ON_ONCE(p4d_present(*p4dp) && !p4d_same(*p4dp, p4d)); \ >>>> +    set_p4d(p4dp, p4d); \ >>>> +}) >>>> + >>>> +#define set_pgd_safe(pgdp, pgd) \ >>>> +({ \ >>>> +    WARN_ON_ONCE(pgd_present(*pgdp) && !pgd_same(*pgdp, pgd)); \ >>>> +    set_pgd(pgdp, pgd); \ >>>> +}) >>>>   #endif /* !__ASSEMBLY__ */ >>>>     #endif /* _ASM_RISCV_PGTABLE_H */ >>>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h >>>> index e39311a89bf4..fefb52bb6b4d 100644 >>>> --- a/arch/x86/include/asm/pgtable.h >>>> +++ b/arch/x86/include/asm/pgtable.h >>>> @@ -1701,6 +1701,43 @@ bool arch_is_platform_page(u64 paddr); >>>>   #define arch_is_platform_page arch_is_platform_page >>>>   #endif >>>>   +/* >>>> + * Use set_p*_safe(), and elide TLB flushing, when confident that *no* >>>> + * TLB flush will be required as a result of the "set". For example, use >>>> + * in scenarios where it is known ahead of time that the routine is >>>> + * setting non-present entries, or re-setting an existing entry to the >>>> + * same value. Otherwise, use the typical "set" helpers and flush the >>>> + * TLB. >>>> + */ >>>> +#define set_pte_safe(ptep, pte) \ >>>> +({ \ >>>> +    WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \ >>>> +    set_pte(ptep, pte); \ >>>> +}) >>>> + >>>> +#define set_pmd_safe(pmdp, pmd) \ >>>> +({ \ >>>> +    WARN_ON_ONCE(pmd_present(*pmdp) && !pmd_same(*pmdp, pmd)); \ >>>> +    set_pmd(pmdp, pmd); \ >>>> +}) >>>> + >>>> +#define set_pud_safe(pudp, pud) \ >>>> +({ \ >>>> +    WARN_ON_ONCE(pud_present(*pudp) && !pud_same(*pudp, pud)); \ >>>> +    set_pud(pudp, pud); \ >>>> +}) >>>> + >>>> +#define set_p4d_safe(p4dp, p4d) \ >>>> +({ \ >>>> +    WARN_ON_ONCE(p4d_present(*p4dp) && !p4d_same(*p4dp, p4d)); \ >>>> +    set_p4d(p4dp, p4d); \ >>>> +}) >>>> + >>>> +#define set_pgd_safe(pgdp, pgd) \ >>>> +({ \ >>>> +    WARN_ON_ONCE(pgd_present(*pgdp) && !pgd_same(*pgdp, pgd)); \ >>>> +    set_pgd(pgdp, pgd); \ >>>> +}) >>>>   #endif    /* __ASSEMBLY__ */ >>> >>> I'm wondering if we can completely get rid of these, for example via: >>> >>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c >>> index d8dbeac8b206..bc71c25930bb 100644 >>> --- a/arch/x86/mm/init_64.c >>> +++ b/arch/x86/mm/init_64.c >>> @@ -79,10 +79,8 @@ DEFINE_POPULATE(pmd_populate_kernel, pmd, pte, init) >>>  static inline void set_##type1##_init(type1##_t *arg1,         \ >>>                         type2##_t arg2, bool init)              \ >>>  {                                                              \ >>> -       if (init)                                               \ >>> -               set_##type1##_safe(arg1, arg2);                 \ >>> -       else                                                    \ >>> -               set_##type1(arg1, arg2);                        \ >>> +       WARN_ON_ONCE(init && ##type1##_present(*arg1) && !##type1##_same(*arg1, arg2)); \ >>> +       set_##type1(arg1, arg2);                                \ >>>  } >>> >>> >>> We might be able to handle the pgd_populate etc part similarly, possibly getting >>> rid of the pgd_populate_safe etc as well. >>> >>> Assuming I don't miss anything important :) >> >> Sounds feasible but will just leave that upto the x86 platform folks to >> change later on, after this patch which just moves these helpers inside >> the platform code. >> >>> >>> Ideally, we get rid of the macros here and just use inline functions ... >>> >> >> Sure, makes sense. Will change these as inline functions. >> >> -#define set_pte_safe(ptep, pte) \ >> -({ \ >> - WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); \ >> - set_pte(ptep, pte); \ >> -}) >> +static inline void set_pte_safe(pte_t *ptep, pte_t pte) >> +{ >> + WARN_ON_ONCE(pte_present(*ptep) && !pte_same(*ptep, pte)); >> + set_pte(ptep, pte); >> +} >> > > This has hit a road block in converting these macros as static inline > functions as suggested earlier, because pmd/pud/p4d/pgd_same() macros > are defined in generic header include/linux/pgtable.h, but way after > gets included. I guess then the current patch should > be left as it is. Just to clarify: My ideas was to get rid of set_pte_safe() *completely* in x86 code, and turn set_pte_init() etc. into inline functions. But we can do that on top, if Dave is fine with this patch. -- Cheers, David / dhildenb