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Wed, 27 Aug 2025 05:57:45 -0700 (PDT) Date: Wed, 27 Aug 2025 05:57:43 -0700 In-Reply-To: <87b10d94-dca2-4ecb-a86f-b38c5c90e0cf@redhat.com> Mime-Version: 1.0 References: <20250729225455.670324-1-seanjc@google.com> <87b10d94-dca2-4ecb-a86f-b38c5c90e0cf@redhat.com> Message-ID: Subject: Re: [PATCH v17 00/24] KVM: Enable mmap() for guest_memfd From: Sean Christopherson To: Paolo Bonzini Cc: Marc Zyngier , Oliver Upton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Ira Weiny , Gavin Shan , Shivank Garg , Vlastimil Babka , Xiaoyao Li , David Hildenbrand , Fuad Tabba , Ackerley Tng , Tao Chan , James Houghton Content-Type: text/plain; charset="us-ascii" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250827_055747_378379_087C91D4 X-CRM114-Status: GOOD ( 19.97 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Aug 27, 2025, Paolo Bonzini wrote: > On 7/30/25 00:54, Sean Christopherson wrote: > > Paolo, > > > > The arm64 patches have been Reviewed-by Marc, and AFAICT the x86 side of > > things is a go. Barring a screwup on my end, this just needs your approval. > > > > Assuming everything looks good, it'd be helpful to get this into kvm/next > > shortly after rc1. The x86 Kconfig changes in particular create semantic > > conflicts with in-flight series. > > > > > > Add support for host userspace mapping of guest_memfd-backed memory for VM > > types that do NOT use support KVM_MEMORY_ATTRIBUTE_PRIVATE (which isn't > > precisely the same thing as CoCo VMs, since x86's SEV-MEM and SEV-ES have > > no way to detect private vs. shared). > > > > mmap() support paves the way for several evolving KVM use cases: > > > > * Allows VMMs like Firecracker to run guests entirely backed by > > guest_memfd [1]. This provides a unified memory management model for > > both confidential and non-confidential guests, simplifying VMM design. > > > > * Enhanced Security via direct map removal: When combined with Patrick's > > series for direct map removal [2], this provides additional hardening > > against Spectre-like transient execution attacks by eliminating the > > need for host kernel direct maps of guest memory. > > > > * Lays the groundwork for *restricted* mmap() support for guest_memfd-backed > > memory on CoCo platforms [3] that permit in-place > > sharing of guest memory with the host. > > > > Based on kvm/queue. > > Applied to kvm/next, thanks! Thank you! FWIW, I did separate run of the patches and came up with the same resolutions for the arm64 changes, so I'm sure they're perfect ;-)