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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id q202-20020a3743d3000000b0073b341148b3sm9483000qka.121.2023.02.20.11.58.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Feb 2023 11:58:10 -0800 (PST) Date: Mon, 20 Feb 2023 11:57:59 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Michael Roth cc: kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, jroedel@suse.de, thomas.lendacky@amd.com, hpa@zytor.com, ardb@kernel.org, pbonzini@redhat.com, seanjc@google.com, vkuznets@redhat.com, jmattson@google.com, luto@kernel.org, dave.hansen@linux.intel.com, slp@redhat.com, pgonda@google.com, peterz@infradead.org, srinivas.pandruvada@linux.intel.com, rientjes@google.com, dovmurik@linux.ibm.com, tobin@ibm.com, bp@alien8.de, vbabka@suse.cz, kirill@shutemov.name, ak@linux.intel.com, tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com, alpergun@google.com, dgilbert@redhat.com, jarkko@kernel.org, ashish.kalra@amd.com, nikunj.dadhania@amd.com, Hugh Dickins Subject: Re: [PATCH RFC v8 18/56] x86/fault: fix handle_split_page_fault() to work with memfd backed pages In-Reply-To: <20230220183847.59159-19-michael.roth@amd.com> Message-ID: <29e9ed33-52eb-fbb4-5358-76939df747a9@google.com> References: <20230220183847.59159-1-michael.roth@amd.com> <20230220183847.59159-19-michael.roth@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 1hzm7oqzxc58k8y1sc14sugd1z494yu9 X-Rspamd-Queue-Id: 4DE85C0011 X-HE-Tag: 1676923092-790323 X-HE-Meta: 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 Fbuq7Fx5 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 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 Mon, 20 Feb 2023, Michael Roth wrote: > From: Hugh Dickins No. > > When the address is backed by a memfd, the code to split the page does > nothing more than remove the PMD from the page tables. So immediately > install a PTE to ensure that any other pages in that 2MB region are > brought back as in 4K pages. > > Signed-off-by: Hugh Dickins No. Suggested-by would be okay. > Cc: Hugh Dickins Thanks. I'm really sorry to be such a jobsworth, and have nothing more constructive to say than I did before in https://lore.kernel.org/linux-mm/7f2228c4-1586-2934-7b92-1a9d23b6046@google.com/ (please re-read), but adding a Signed-off-by where none was given is wrong; and I'm not ever going to comprehend enough of the context to give it. Best of luck for the series, Hugh > Signed-off-by: Ashish Kalra > Signed-off-by: Michael Roth > --- > mm/memory.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/memory.c b/mm/memory.c > index e68da7e403c6..33c9020ba1f8 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -4999,6 +4999,11 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf) > static int handle_split_page_fault(struct vm_fault *vmf) > { > __split_huge_pmd(vmf->vma, vmf->pmd, vmf->address, false, NULL); > + /* > + * Install a PTE immediately to ensure that any other pages in > + * this 2MB region are brought back in as 4K pages. > + */ > + __pte_alloc(vmf->vma->vm_mm, vmf->pmd); > return 0; > } > > -- > 2.25.1