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Mon, 8 Dec 2025 11:07:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id POYKI1SxNmkpeQAAD6G6ig (envelope-from ); Mon, 08 Dec 2025 11:07:00 +0000 Message-ID: <5649e224-bb6a-4b63-bb27-5541216df0b6@suse.cz> Date: Mon, 8 Dec 2025 12:07:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 3/3] KVM: guest_memfd: GUP source pages prior to populating guest memory Content-Language: en-US To: Michael Roth , FirstName LastName Cc: ackerleytng@google.com, aik@amd.com, ashish.kalra@amd.com, david@redhat.com, ira.weiny@intel.com, kvm@vger.kernel.org, liam.merwick@oracle.com, linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, seanjc@google.com, thomas.lendacky@amd.com, yan.y.zhao@intel.com References: <20251203142648.trx6sslxvxr26yzd@amd.com> <20251203205910.1137445-1-vannapurve@google.com> <20251203231208.vsoibqhlosy2cjxs@amd.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: B52B6140002 X-Stat-Signature: 53gz3dozq7saokbwzaqp6ykbu3cbj693 X-Rspam-User: X-HE-Tag: 1765192023-895244 X-HE-Meta: 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 XEqU5Ox0 BTnwGNtDwYghgngL42shghl2aemoCXH73eR/JZ74gnwUcdwYQWv8WzR/ZqdgeMGydKPSuADMc0/9c+1QkPd50VHGLA7ewfu2Er6xzOYmHcYBSvKYNj5iCYSKjtYTbOlX/4Bw50CnhHUd/sI8kHeO+Vh7A2RJjs7/GfX6N0SbFCpjMVdCgYYgzjpgcuH7GLRgcipuK57vNbmDvq1PstP7CtXh3B92hYK8Kebz4aeuIrilP9+170AoWQAqPE9sm1GpWvJUpBY1CeDXd1mvq3sQibkktq3X7mdkkt9E6lfa8sEYDXbpFtU+WJm+2ep0EEFtQrEWfpzLoP4I8YVbaWt7bRYB6rA== 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: List-Subscribe: List-Unsubscribe: On 12/4/25 00:12, Michael Roth wrote: > On Wed, Dec 03, 2025 at 08:59:10PM +0000, FirstName LastName wrote: >> >> e.g. 4K page based population logic will keep things simple and can be >> further simplified if we can add PAGE_ALIGNED(params.uaddr) restriction. > > I'm still hesitant to pull the trigger on retroactively enforcing > page-aligned uaddr for SNP, but if the maintainers are good with it then > no objection from me. IMHO it would be for the best. If there are no known users that would break, it's worth trying. The "do not break userspace" rule isn't about eliminating any theoretical possibility, but indeed about known breakages (and reacting appropriately to reports about previously unknown breakages). Perhaps any such users would be also willing to adjust and not demand a revert.