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

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Thu, May 11, 2023 at 11:22 AM Marek Marczykowski-Górecki
<marmarek@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> 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@xxxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxx>
> >
> > 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?

Your series fixes the problem!

I just had the details from the original issue, so I included them.  I
was trying to highlight what this series fixed for me.  Sorry for the
confusion.

Regards,
Jason