On Mon, Apr 28, 2025 at 01:00:01PM -0700, Stefano Stabellini wrote: > On Mon, 28 Apr 2025, Jan Beulich wrote: > > On 25.04.2025 22:19, Stefano Stabellini wrote: > > > From: Xenia Ragiadakou <xenia.ragiada...@amd.com> > > > > > > Dom0 PVH might need XENMEM_exchange when passing contiguous memory > > > addresses to firmware or co-processors not behind an IOMMU. > > > > I definitely don't understand the firmware part: It's subject to the > > same transparent P2M translations as the rest of the VM; it's just > > another piece of software running there. > > > > "Co-processors not behind an IOMMU" is also interesting; a more > > concrete scenario might be nice, yet I realize you may be limited in > > what you're allowed to say. > > Sure. On AMD x86 platforms there is a co-processor called PSP running > TEE firmware. The PSP is not behind an IOMMU. Dom0 needs occasionally to > pass addresses to it. See drivers/tee/amdtee/ and > include/linux/psp-tee.h in Linux.
We had (have?) similar issue with amdgpu (for integrated graphics) - it uses PSP for loading its firmware. With PV dom0 there is a workaround as dom0 kinda knows MFN. I haven't tried PVH dom0 on such system yet, but I expect troubles (BTW, hw1 aka zen2 gitlab runner has amdgpu, and it's the one I used for debugging this issue). References: https://lists.xenproject.org/archives/html/xen-devel/2022-06/msg01660.html https://github.com/QubesOS/qubes-issues/issues/6923 -- Best Regards, Marek Marczykowski-Górecki Invisible Things Lab
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