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Fri, 21 Jul 2023 15:33:17 -0700 (PDT) Date: Fri, 21 Jul 2023 15:33:15 -0700 In-Reply-To: <20230721222704.GJ25699@ls.amr.corp.intel.com> Mime-Version: 1.0 References: <20230718234512.1690985-1-seanjc@google.com> <20230718234512.1690985-13-seanjc@google.com> <20230721061314.3ls6stdawz53drv3@yy-desk-7060> <20230721222704.GJ25699@ls.amr.corp.intel.com> Message-ID: Subject: Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for guest-specific backing memory From: Sean Christopherson To: Isaku Yamahata Cc: Yuan Yao , Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , "Matthew Wilcox (Oracle)" , Andrew Morton , Paul Moore , James Morris , "Serge E. Hallyn" , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, Chao Peng , Fuad Tabba , Jarkko Sakkinen , Yu Zhang , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , Vlastimil Babka , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , "Kirill A . Shutemov" Content-Type: text/plain; charset="us-ascii" X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0CD402000A X-Stat-Signature: 51ubfmwt867brgg9p93c4pbyjgirxbi1 X-Rspam-User: X-HE-Tag: 1689978797-714087 X-HE-Meta: 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 uyX7v6+6 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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 Fri, Jul 21, 2023, Isaku Yamahata wrote: > On Fri, Jul 21, 2023 at 02:13:14PM +0800, > Yuan Yao wrote: > > > +static int kvm_gmem_error_page(struct address_space *mapping, struct page *page) > > > +{ > > > + struct list_head *gmem_list = &mapping->private_list; > > > + struct kvm_memory_slot *slot; > > > + struct kvm_gmem *gmem; > > > + unsigned long index; > > > + pgoff_t start, end; > > > + gfn_t gfn; > > > + > > > + filemap_invalidate_lock_shared(mapping); > > > + > > > + start = page->index; > > > + end = start + thp_nr_pages(page); > > > + > > > + list_for_each_entry(gmem, gmem_list, entry) { > > > + xa_for_each_range(&gmem->bindings, index, slot, start, end - 1) { > > > + for (gfn = start; gfn < end; gfn++) { > > > > Why the start end range used as gfn here ? Math is hard? I almost always mess up these types of things, and then catch my bugs via tests. But I don't have tests for this particular flow... Which reminds me, we need tests for this :-) Hopefully error injection provides most of what we need? > > the page->index is offset of inode's page cache mapping and > > gmem address space, IIUC, gfn calculation should follow same > > way as kvm_gmem_invalidate_begin(). > > Also instead of sending signal multiple times, we can utilize lsb argument. As Vishal pointed out, this code shouldn't be sending signals in the first place.