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([2001:b07:6468:f312:b509:fc01:ee8a:ca8a]) by smtp.gmail.com with ESMTPSA id b67sm4417502wmc.38.2020.01.21.06.40.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 21 Jan 2020 06:40:44 -0800 (PST) Subject: Re: [PATCH 07/14] KVM: x86/mmu: Walk host page tables to find THP mappings To: Sean Christopherson Cc: Paul Mackerras , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Andrew Morton , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, syzbot+c9d1fb51ac9d0d10c39d@syzkaller.appspotmail.com, Andrea Arcangeli , Dan Williams , Barret Rhoden , David Hildenbrand , Jason Zeng , Dave Jiang , Liran Alon , linux-nvdimm References: <20200108202448.9669-1-sean.j.christopherson@intel.com> <20200108202448.9669-8-sean.j.christopherson@intel.com> From: Paolo Bonzini Message-ID: <6e9987a2-c34f-362d-a123-7dc4849811d1@redhat.com> Date: Tue, 21 Jan 2020 15:40:43 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20200108202448.9669-8-sean.j.christopherson@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/01/20 21:24, Sean Christopherson wrote: > + > + /* > + * Manually do the equivalent of kvm_vcpu_gfn_to_hva() to avoid the > + * "writable" check in __gfn_to_hva_many(), which will always fail on > + * read-only memslots due to gfn_to_hva() assuming writes. Earlier > + * page fault steps have already verified the guest isn't writing a > + * read-only memslot. > + */ > + slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); > + if (!memslot_valid_for_gpte(slot, true)) > + return PT_PAGE_TABLE_LEVEL; > + > + hva = __gfn_to_hva_memslot(slot, gfn); > + Using gfn_to_memslot_dirty_bitmap is also a good excuse to avoid kvm_vcpu_gfn_to_hva. + slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, true); + if (!slot) + return PT_PAGE_TABLE_LEVEL; + + hva = __gfn_to_hva_memslot(slot, gfn); (I am planning to remove gfn_to_hva_memslot so that __gfn_to_hva_memslot can lose the annoying underscores). Paolo