On Tue, Jul 29, 2025 at 11:29:17AM -0300, Jason Gunthorpe wrote: > On Tue, Jul 29, 2025 at 01:58:54PM +0530, Aneesh Kumar K.V wrote: > > Jason Gunthorpe <jgg@xxxxxxxx> writes: > > > > > On Mon, Jul 28, 2025 at 07:21:43PM +0530, Aneesh Kumar K.V (Arm) wrote: > > >> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@xxxxxxxxxx> > > > > > > Why would we need this? > > > > > > I can sort of understand why Intel would need it due to their issues > > > with MCE, but ARM shouldn't care either way, should it? > > > > > > But also why is it an iommufd option? That doesn't seem right.. > > > > > > Jason > > > > This is based on our previous discussion https://lore.kernel.org/all/20250606120919.GH19710@xxxxxxxxxx > > I suggested a global option, this is a per-device option, and that > especially seems wrong for iommufd. If it is per-device that is vfio, I think this should be per-device. The original purpose of this pci_region_request_*() is to prevent further mmap/read/write against a vfio_cdev FD which would be used for private assignment. You shouldn't prevent all other devices from working with userspace APPs (e.g. DPDK) if there is one private assignment in system. > if it is global then vfio can pick it up during the early phases of > opening the device. > > > IIUC, we intend to request the resource in exclusive mode for secure > > guests—regardless of whether the platform is Intel or ARM. Could you > > help clarify the MCE issue observed on Intel platforms in this context? > > As I understand it Intel MCEs if the non-secure side ever reads from > secure'd address space. So there is alot of emphasis there to ensure Yeah, Intel TDX doesn't have a lower access control table for CC. So if host reads, the TLP sends and MCE happens. Thanks, Yilun > there are no CPU mappings. > > Jason
