Re: [PATCH] x86/CPU/AMD: Don't print reset reason in VMs

[Juergen Gross]

On 04.11.26 02:30, Jason Andryuk wrote:
> print_s5_reset_status_mmio() expects to read FCH MMIO on baremetal.  VMs
> don't have emulated FCH registers, so there is nothing to check.  Add an
> early exit when running on a hypervisor.
>
> The real motivation is Xen PV domUs can't boot on Zen CPUs.  PV domUs
> PTE contain system physical addresses - they don't have concept of guest
> physical addresses.  domUs can only map physical addresses they are
> assigned, so a domU fails to map the FCH MMIO addresses.  However
> set_pte() does not return failure, so ioremap() returns a pointer while
> the PTEs are unpopulated.  print_s5_reset_status_mmio() faults when
> reading through the pointer, breaking the boot.  This change fixes Xen
> PV domUs booting on Zen CPUs.
>
> dom0 can map the FCH MMIO, but it has X86_FEATURE_HYPERVISOR set.  With
> this change, it no longer prints the reset reason.
>
> Fixes: ab8131028710 ("x86/CPU/AMD: Print the reason for the last reset")
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Borislav Petkov <bp@xxxxxxxxx>
> Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>


Juergen

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