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[99.254.121.117]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-45682c82a52sm7101381cf.16.2024.08.29.11.26.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 29 Aug 2024 11:26:24 -0700 (PDT) Date: Thu, 29 Aug 2024 14:26:22 -0400 From: Peter Xu To: David Hildenbrand 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 Subject: Re: [PATCH v2 07/19] mm/fork: Accept huge pfnmap entries Message-ID: References: <20240826204353.2228736-1-peterx@redhat.com> <20240826204353.2228736-8-peterx@redhat.com> <78d77162-11df-4437-b70b-fa04f868a494@redhat.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <78d77162-11df-4437-b70b-fa04f868a494@redhat.com> 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. -- Peter Xu