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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@vger.kernel.org > Suggested-by: Borislav Petkov > Signed-off-by: Jason Andryuk > --- > dom0 could work, but that would require a xen_initial_domain() check. > > I've wondered about a different approach: We can't directly check for a > device for the FCH_PM_BASE memory, but maybe we could check for a PCI > ISA Bridge with PCI_VENDOR_ID_AMD. That might be close enough to > indicate real hardware? But it would still be a heuristic, so I'm not > sure how much better that would be. Maybe, I had an older version that used the smbus device / i2c driver. https://lore.kernel.org/all/20230407203720.18184-1-yazen.ghannam@amd.com/ Is this available in dom0? > --- > arch/x86/kernel/cpu/amd.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c > index 40463bad1078..580ccc2ce5fc 100644 > --- a/arch/x86/kernel/cpu/amd.c > +++ b/arch/x86/kernel/cpu/amd.c > @@ -1357,7 +1357,8 @@ static __init int print_s5_reset_status_mmio(void) > u32 value; > int i; > > - if (!cpu_feature_enabled(X86_FEATURE_ZEN)) > + if (!cpu_feature_enabled(X86_FEATURE_ZEN) || > + cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) > return 0; > > addr = ioremap(FCH_PM_BASE + FCH_PM_S5_RESET_STATUS, sizeof(value)); > -- Reviewed-by: Yazen Ghannam Thanks, Yazen