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[2003:cb:c711:c600:c1d6:7158:f946:f083]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42bacaac810sm44098825e9.33.2024.08.29.12.44.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 29 Aug 2024 12:44:02 -0700 (PDT) Message-ID: <32a451ee-6836-4d4d-814c-752c15415aae@redhat.com> Date: Thu, 29 Aug 2024 21:44:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 07/19] mm/fork: Accept huge pfnmap entries To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Gavin Shan , Catalin Marinas , x86@kernel.org, Ingo Molnar , Andrew Morton , Paolo Bonzini , Dave Hansen , Thomas Gleixner , Alistair Popple , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Sean Christopherson , Oscar Salvador , Jason Gunthorpe , Borislav Petkov , Zi Yan , Axel Rasmussen , Yan Zhao , Will Deacon , Kefeng Wang , Alex Williamson References: <20240826204353.2228736-1-peterx@redhat.com> <20240826204353.2228736-8-peterx@redhat.com> <78d77162-11df-4437-b70b-fa04f868a494@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240829_124408_148243_16CFD143 X-CRM114-Status: GOOD ( 16.63 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 29.08.24 20:26, Peter Xu wrote: > On Thu, Aug 29, 2024 at 05:10:42PM +0200, David Hildenbrand wrote: >> On 26.08.24 22:43, Peter Xu wrote: >>> Teach the fork code to properly copy pfnmaps for pmd/pud levels. Pud is >>> much easier, the write bit needs to be persisted though for writable and >>> shared pud mappings like PFNMAP ones, otherwise a follow up write in either >>> parent or child process will trigger a write fault. >>> >>> Do the same for pmd level. >>> >>> Signed-off-by: Peter Xu >>> --- >>> mm/huge_memory.c | 29 ++++++++++++++++++++++++++--- >>> 1 file changed, 26 insertions(+), 3 deletions(-) >>> >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index e2c314f631f3..15418ffdd377 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -1559,6 +1559,24 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, >>> pgtable_t pgtable = NULL; >>> int ret = -ENOMEM; >>> + pmd = pmdp_get_lockless(src_pmd); >>> + if (unlikely(pmd_special(pmd))) { >> >> I assume I have to clean up your mess here as well? > > Can you leave meaningful and explicit comment? I'll try to address. Sorry Peter, but I raised all that as reply to v1. For example, I stated that vm_normal_page_pmd() already *exist* and why these pmd_special() checks should be kept there. I hear you, you're not interested in cleaning that up. So at this point it's easier for me to clean it up myself. -- Cheers, David / dhildenb