Re: [PATCH] x86/CPU/AMD: avoid printing reset reasons on Xen domU

[Borislav Petkov <bp@xxxxxxxxx>]

On Fri, Dec 19, 2025 at 09:36:45AM -0800, Sean Christopherson wrote:
> @@ -301,6 +303,20 @@ __ioremap_caller(resource_size_t phys_addr, unsigned 
> long size,
>         if (ioremap_page_range(vaddr, vaddr + size, phys_addr, prot))
>                 goto err_free_area;
>  
> +       /*
> +        * Verify the range was actually mapped when running as a Xen PV DomU
> +        * guest.  Xen PV doesn't emulate a virtual chipset/motherboard, and
> +        * disallows DomU from mapping host physical addresses that the domain
> +        * doesn't own.  Unfortunately, the PTE APIs assume success, and so
> +        * Xen's rejection of the mapping is ignored.
> +        */
> +       if (xen_pv_domain() && !xen_initial_domain()) {
> +               int level;
> +
> +               if (!lookup_address(vaddr, &level))
> +                       goto err_free_area;
> +       }

This activates my ancient allergies caused by the sprinkling "if (XEN)"
randomly across the kernel tree. If this is a PV guest there probably
should be a PV ioremap variant which hides all that gunk away...

Thx.

-- 
Regards/Gruss,
    Boris.

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