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Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 Subject: Re: [PATCH rfc -next 01/10] mm: add a generic VMA lock-based page fault handler Content-Language: en-US From: Kefeng Wang To: Suren Baghdasaryan , Matthew Wilcox CC: , Andrew Morton , Russell King , Catalin Marinas , Will Deacon , Huacai Chen , WANG Xuerui , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , , , , , , , References: <20230713095339.189715-1-wangkefeng.wang@huawei.com> <20230713095339.189715-2-wangkefeng.wang@huawei.com> <6f06f7d5-7d84-815e-699b-eef684e014b0@huawei.com> In-Reply-To: <6f06f7d5-7d84-815e-699b-eef684e014b0@huawei.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected X-Rspamd-Queue-Id: CB94B140013 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: edpzx4oe8g5gypi5hyrbrdqbeua8ehc8 X-HE-Tag: 1689386084-416977 X-HE-Meta: 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 QF2dw901 X97XNrpRZldD1yRo1nBrTUT6WKqDf8C0GTl48tLXEY88yI2aK2Jl86JDE0pf86G5bJVFpQ5J7CXMEJli/tCUxEiCVw4YvoVOXrU+aExYEtrDXaOw+5pSlbfaoR4/Wmax6AgHO8LtqU7k+g8q3UROFl9QlWAf368+PjCcgooxic/8+W9fe7xYxTukmVMJ1o4oY2eC0 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 2023/7/14 9:52, Kefeng Wang wrote: > > > On 2023/7/14 4:12, Suren Baghdasaryan wrote: >> On Thu, Jul 13, 2023 at 9:15 AM Matthew Wilcox >> wrote: >>> >>>> +int try_vma_locked_page_fault(struct vm_locked_fault *vmlf, >>>> vm_fault_t *ret) >>>> +{ >>>> +     struct vm_area_struct *vma; >>>> +     vm_fault_t fault; >>> >>> >>> On Thu, Jul 13, 2023 at 05:53:29PM +0800, Kefeng Wang wrote: >>>> +#define VM_LOCKED_FAULT_INIT(_name, _mm, _address, _fault_flags, >>>> _vm_flags, _regs, _fault_code) \ >>>> +     _name.mm                = _mm;                  \ >>>> +     _name.address           = _address;             \ >>>> +     _name.fault_flags       = _fault_flags;         \ >>>> +     _name.vm_flags          = _vm_flags;            \ >>>> +     _name.regs              = _regs;                \ >>>> +     _name.fault_code        = _fault_code >>> >>> More consolidated code is a good idea; no question.  But I don't think >>> this is the right way to do it. > > I agree it is not good enough, but the arch's vma check acess has > different implementation, some use vm flags, some need fault code and > regs, and some use both :( > >>> >>>> +int __weak arch_vma_check_access(struct vm_area_struct *vma, >>>> +                              struct vm_locked_fault *vmlf); >>> >>> This should be: >>> >>> #ifndef vma_check_access >>> bool vma_check_access(struct vm_area_struct *vma, ) >>> { >>>          return (vma->vm_flags & vm_flags) == 0; >>> } >>> #endif >>> >>> and then arches which want to do something different can just define >>> vma_check_access. > > Ok, I could convert to use this way. > >>> >>>> +int try_vma_locked_page_fault(struct vm_locked_fault *vmlf, >>>> vm_fault_t *ret) >>>> +{ >>>> +     struct vm_area_struct *vma; >>>> +     vm_fault_t fault; >>> >>> Declaring the vmf in this function and then copying it back is just >>> wrong. >>> We need to declare vm_fault_t earlier (in the arch fault handler) and >>> pass it in. > > Actually I passed the vm_fault_t *ret(in the arch fault handler), we > could directly use *ret instead of a new local variable, and no copy. >> >> Did you mean to say "we need to declare vmf (struct vm_fault) earlier >> (in the arch fault handler) and pass it in." ? After recheck the code, I think Matthew' idea is 'declare vmf (struct vm_fault) earlier' like Suren said, not vm_fault_t, right? will try this, thanks. >> >>>   I don't think that creating struct vm_locked_fault is the >>> right idea either. > > As mentioned above for vma check access, we need many arguments for a > function, a new struct looks possible better, is there better solution > or any suggestion? > > Thanks. >