On 15.04.2025 12:40, Marek Marczykowski wrote: > On Tue, Apr 15, 2025 at 12:18:04PM +0200, Jan Beulich wrote: >> On 15.04.2025 12:04, Roger Pau Monné wrote: >>> On Tue, Apr 15, 2025 at 11:41:27AM +0200, Jan Beulich wrote: >>>> On 15.04.2025 10:34, Roger Pau Monné wrote: >>>>> Emulation of r/o MMIO accesses failing wouldn't be an issue from Xen's >>>>> perspective, that would "just" result in the guest getting a #GP >>>>> injected. >>>> >>>> That's not the part I'm worried about. What worries me is that we open up >>>> another (or better: we're widening a) way to hit the emulator in the first >>>> place. (Plus, as said, the issue with the not really tidy P2M type system.) >>> >>> But the hit would be limited to domains having r/o p2m_mmio_direct >>> entries in the p2m, as otherwise the path would be unreachable? >> >> I fear I don't follow - all you look for in the newly extended conditional >> is the type being p2m_mmio_direct. There's no r/o-ness being checked for >> until we'd make it through the emulator and into subpage_mmio_accept(). > > But EPT violation can be hit on p2m_mmio_direct page only if it's a > write and the page is read-only, no? Is there any other case that exists > today?
Today and if everything works as it should - yes, I think so. Jan
