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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id k14sm9384097pga.65.2021.11.23.07.36.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Nov 2021 07:36:38 -0800 (PST) Date: Tue, 23 Nov 2021 15:36:35 +0000 From: Sean Christopherson To: Borislav Petkov Cc: Dave Hansen , Brijesh Singh , Peter Gonda , 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 , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , 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 00/45] Add AMD Secure Nested Paging (SEV-SNP) Hypervisor Support Message-ID: References: <20210820155918.7518-1-brijesh.singh@amd.com> <5f3b3aab-9ec2-c489-eefd-9136874762ee@intel.com> <38282b0c-7eb5-6a91-df19-2f4cfa8549ce@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 23, 2021, Borislav Petkov wrote: > On Mon, Nov 22, 2021 at 02:51:35PM -0800, Dave Hansen wrote: > > By "supporting", do you mean doing something functional? I don't really > > care if ptrace() to guest private memory returns -EINVAL or whatever. > > The most important thing is not crashing the host. > > > > Also, as Sean mentioned, this isn't really about ptrace() itself. It's > > really about ensuring that no kernel or devices accesses to guest > > private memory can induce bad behavior. > > I keep repeating this suggestion of mine that we should treat > guest-private pages as hw-poisoned pages which have experienced a > uncorrectable error in the past. > > mm already knows how to stay away from those. Kirill posted a few RFCs that did exactly that. It's definitely a viable approach, but it's a bit of a dead end, e.g. doesn't help solve page migration, is limited to struct page, doesn't capture which KVM guest owns the memory, etc... https://lore.kernel.org/kvm/20210416154106.23721-1-kirill.shutemov@linux.intel.com/