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Tsirkin" To: David Woodhouse Cc: Richard Cochran , Peter Hilber , linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-rtc@vger.kernel.org, "Ridoux, Julien" , virtio-dev@lists.linux.dev, "Luu, Ryan" , "Chashper, David" , "Mohamed Abuelfotoh, Hazem" , "Christopher S . Hall" , Jason Wang , John Stultz , netdev@vger.kernel.org, Stephen Boyd , Thomas Gleixner , Xuan Zhuo , Marc Zyngier , Mark Rutland , Daniel Lezcano , Alessandro Zummo , Alexandre Belloni , qemu-devel , Simon Horman Subject: Re: [PATCH] ptp: Add vDSO-style vmclock support Message-ID: <20240726015613-mutt-send-email-mst@kernel.org> References: <20240725100351-mutt-send-email-mst@kernel.org> <2a27205bfc61e19355d360f428a98e2338ff68c3.camel@infradead.org> <20240725122603-mutt-send-email-mst@kernel.org> <0959390cad71b451dc19e5f9396d3f4fdb8fd46f.camel@infradead.org> <20240725163843-mutt-send-email-mst@kernel.org> <20240725170328-mutt-send-email-mst@kernel.org> <20240725174327-mutt-send-email-mst@kernel.org> <9261e393083bcd151a017a5af3345a1364b3e0f3.camel@infradead.org> Precedence: bulk X-Mailing-List: linux-rtc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9261e393083bcd151a017a5af3345a1364b3e0f3.camel@infradead.org> On Thu, Jul 25, 2024 at 11:20:56PM +0100, David Woodhouse wrote: > We're rolling out the AMZNVCLK device for internal use cases, and plan > to add it in public instances some time later. Let's be real. If amazon does something in its own hypervisor, and the only way to use that is to expose the interface to userspace, there is very little the linux community can do. Moreover, userspace will be written to this ABI, and be locked in to the specific hypervisor. It might be a win for amazon short term but long term you will want to extend things and it will be a mess. So I feel you have chosen ACPI badly. It just does not have the APIs that you need. Virtio does, and would not create a userpspace lock-in to a specific hypervisor. It's not really virtio specific either, you can write a bare pci device with a BAR and a bunch of msix vectors and it will get you the same effect. -- MST