Re: [PATCH 1/2] x86/emul: dump unhandled memory accesses for PVH dom0

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.02.2025 10:29, Roger Pau Monne wrote:
> A PV dom0 can map any host memory as long as it's allowed by the IO
> capability range in d->iomem_caps.  On the other hand, a PVH dom0 has no
> way to populate MMIO region onto it's p2m, so it's limited to what Xen
> initially populates on the p2m based on the host memory map and the enabled
> device BARs.
> 
> Introduce a new debug build only printk that reports attempts by dom0 to
> access addresses not populated on the p2m, and not handled by any emulator.
> This is for information purposes only, but might allow getting an idea of
> what MMIO ranges might be missing on the p2m.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Hmm, yes, why not:
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
with one suggestion:

> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -337,6 +337,9 @@ static int hvmemul_do_io(
>          /* If there is no suitable backing DM, just ignore accesses */
>          if ( !s )
>          {
> +            if ( is_mmio && is_hardware_domain(currd) )
> +                gdprintk(XENLOG_DEBUG, "unhandled memory %s to %#lx size 
> %u\n",
> +                         dir ? "read" : "write", addr, size);

Can we make it "read from" and "write to"?

Jan