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AJvYcCWgqTcATTfEVvtlrNU6660sme6idmh1GkkQC1lWnojKeBV2pM4OuxJ6Oie9FLJdGUEyn203AX5AZg==@kvack.org X-Gm-Message-State: AOJu0Yz3scufyE5MKwLcljuvr0MPUxuL3JkTR7xFkgiWvHFkuCepEStl rkWA6D935nHFqISuWa98RMJcmum+oLgDaHQszCR2mvV6stG6T5/CFefsWxZ4TnjgmOS2NtebDb5 9Mj0MTQ== X-Google-Smtp-Source: AGHT+IHCoAoYGyPw5j9JBku0hHTxP/A4fWJZOerFAj0Mbk5JHgReKtVWkoA09cZ+6DnOUbpNy+4DPxRjdBM= X-Received: from pjtd13.prod.google.com ([2002:a17:90b:4d:b0:349:d3b1:8ea4]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:3394:b0:35e:2a82:fdf4 with SMTP id adf61e73a8af0-366e2fb7523mr592380637.59.1765330223201; Tue, 09 Dec 2025 17:30:23 -0800 (PST) Date: Tue, 9 Dec 2025 17:30:21 -0800 In-Reply-To: <5649e224-bb6a-4b63-bb27-5541216df0b6@suse.cz> Mime-Version: 1.0 References: <20251203142648.trx6sslxvxr26yzd@amd.com> <20251203205910.1137445-1-vannapurve@google.com> <20251203231208.vsoibqhlosy2cjxs@amd.com> <5649e224-bb6a-4b63-bb27-5541216df0b6@suse.cz> Message-ID: Subject: Re: [PATCH 3/3] KVM: guest_memfd: GUP source pages prior to populating guest memory From: Sean Christopherson To: Vlastimil Babka Cc: Michael Roth , FirstName LastName , 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, thomas.lendacky@amd.com, yan.y.zhao@intel.com Content-Type: text/plain; charset="us-ascii" X-Stat-Signature: oq4opjf8ex16inqqt3o646gitq3ufmbi X-Rspamd-Queue-Id: A5D26C0013 X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1765330224-241538 X-HE-Meta: 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 tBP0genk 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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: List-Subscribe: List-Unsubscribe: On Mon, Dec 08, 2025, Vlastimil Babka wrote: > 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. +1. This code is already crazy complex, we should jump at any simplification possible. Especially since we expect in-place conversion to dominate usage in the future, and in-place conversion is incompatible with an unaligned source.