Re: [PATCH v2 0/2] Add API for making parts of a MMIO page R/O and use it in XHCI console

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

[-- Attachment #1: Type: text/plain, Size: 1769 bytes --]

On Thu, May 11, 2023 at 10:58:48AM -0400, Jason Andryuk wrote:
> On Fri, May 5, 2023 at 5:26 PM Marek Marczykowski-Górecki
> <marmarek@invisiblethingslab.com> wrote:
> >
> > On older systems, XHCI xcap had a layout that no other (interesting) registers
> > were placed on the same page as the debug capability, so Linux was fine with
> > making the whole page R/O. But at least on Tiger Lake and Alder Lake, Linux
> > needs to write to some other registers on the same page too.
> >
> > Add a generic API for making just parts of an MMIO page R/O and use it to fix
> > USB3 console with share=yes or share=hwdom options. More details in commit
> > messages.
> >
> > Marek Marczykowski-Górecki (2):
> >   x86/mm: add API for marking only part of a MMIO page read only
> >   drivers/char: Use sub-page ro API to make just xhci dbc cap RO
> 
> Series:
> Tested-by: Jason Andryuk <jandryuk@gmail.com>
> 
> I had the issue with a 10th Gen, Comet Lake, laptop.  With an HVM
> usbvm with dbgp=xhci,share=1, Xen crashed the domain because of:
> (XEN) d1v0 EPT violation 0xdaa (-w-/r-x) gpa 0x000000f1008470 mfn 0xcc328 type 5

Hmm, this series is supposed to avoid exactly this issue. I tested it on
12th Gen, so maybe 10th Gen has a bit different layout.
Can you add a debug print before subpage_mmio_ro_add() call in
xhci-dbc.c and see what area is getting protected?

> The BAR is mfn 0xcc320-0xcc32f
> 
> Booting PV, it faulted at drivers/usb/host/pci-quirks.c:1170 which looks to be:
> ```
> /* Disable any BIOS SMIs and clear all SMI events*/
> writel(val, base + ext_cap_offset + XHCI_LEGACY_CONTROL_OFFSET);
> ```
> 
> Thanks for integrating XUE, Marek!

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]