On 29.01.2025 14:32, Bjorn Helgaas wrote: > 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? The hypervisor only intercepts config space writes; reads, particularly when going via mmcfg, ought to be unaffected, and hence what lspci shows should be "the actual hardware config". Jan
