Re: Config space access to Mediatek MT7922 doesn't work after device reset in Xen PV dom0 (regression, Linux 6.12)

[Bjorn Helgaas]

On Wed, Jan 29, 2025 at 04:47:28AM +0100, Marek Marczykowski-Górecki wrote:
> On Tue, Jan 28, 2025 at 09:40:18PM -0600, Bjorn Helgaas wrote:
> > I guess the code at [2] is running in user mode and uses Linux
> > syscalls for config access?  Is it straceable?
> 
> Nope, it's running as the hypervisor and mediates Linux's access to the
> hardware. In fact, Linux PV kernel (which dom0 is by default under Xen)
> is running in ring 3...
> 
> But I can add some more logging there.

So I guess the hypervisor performs the config access on behalf of the
Linux PV kernel?  Obviously Linux thinks CRS/RRS SV is enabled, but I
suppose all the lspci output is similarly based on whatever the
hypervisor does, so how do we know the actual hardware config?

> > > [2] https://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/arch/x86/pv/emul-priv-op.c;h=70150c27227661baa253af8693ff00f2ab640a98;hb=HEAD#l295