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[82.29.118.27]) by smtp.gmail.com with ESMTPSA id h15sm5740773wrc.19.2021.09.23.10.18.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Sep 2021 10:18:32 -0700 (PDT) Date: Thu, 23 Sep 2021 18:18:29 +0100 From: "Dr. David Alan Gilbert" To: Brijesh Singh Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, linux-crypto@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Gonda , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com Subject: Re: [PATCH Part2 v5 26/45] KVM: SVM: Mark the private vma unmerable for SEV-SNP guests Message-ID: References: <20210820155918.7518-1-brijesh.singh@amd.com> <20210820155918.7518-27-brijesh.singh@amd.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 In-Reply-To: <20210820155918.7518-27-brijesh.singh@amd.com> User-Agent: Mutt/2.0.7 (2021-05-04) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline * Brijesh Singh (brijesh.singh@amd.com) wrote: > When SEV-SNP is enabled, the guest private pages are added in the RMP > table; while adding the pages, the rmp_make_private() unmaps the pages > from the direct map. If KSM attempts to access those unmapped pages then > it will trigger #PF (page-not-present). > > Encrypted guest pages cannot be shared between the process, so an > userspace should not mark the region mergeable but to be safe, mark the > process vma unmerable before adding the pages in the RMP table. ^^^^^^^^^ (and in the subject) -> unmergeable > > Signed-off-by: Brijesh Singh > --- > arch/x86/kvm/svm/sev.c | 32 ++++++++++++++++++++++++++++++++ > 1 file changed, 32 insertions(+) > > diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c > index 4b126598b7aa..dcef0ae5f8e4 100644 > --- a/arch/x86/kvm/svm/sev.c > +++ b/arch/x86/kvm/svm/sev.c > @@ -18,11 +18,13 @@ > #include > #include > #include > +#include > #include > > #include > #include > #include > +#include > > #include "x86.h" > #include "svm.h" > @@ -1683,6 +1685,30 @@ static bool is_hva_registered(struct kvm *kvm, hva_t hva, size_t len) > return false; > } > > +static int snp_mark_unmergable(struct kvm *kvm, u64 start, u64 size) ^^^^^^^^^^ > +{ > + struct vm_area_struct *vma; > + u64 end = start + size; Do you need to worry about wrap there? (User supplied start/size?) Dave > + int ret; > + > + do { > + vma = find_vma_intersection(kvm->mm, start, end); > + if (!vma) { > + ret = -EINVAL; > + break; > + } > + > + ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, > + MADV_UNMERGEABLE, &vma->vm_flags); > + if (ret) > + break; > + > + start = vma->vm_end; > + } while (end > vma->vm_end); > + > + return ret; > +} > + > static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) > { > struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; > @@ -1707,6 +1733,12 @@ static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp) > if (!is_hva_registered(kvm, params.uaddr, params.len)) > return -EINVAL; > > + mmap_write_lock(kvm->mm); > + ret = snp_mark_unmergable(kvm, params.uaddr, params.len); > + mmap_write_unlock(kvm->mm); > + if (ret) > + return -EFAULT; > + > /* > * The userspace memory is already locked so technically we don't > * need to lock it again. Later part of the function needs to know > -- > 2.17.1 > > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK