On 11.02.2026 18:51, Alejandro Vallejo wrote:
> On Wed Feb 11, 2026 at 5:06 PM CET, Jan Beulich wrote:
>> On 06.02.2026 17:15, Alejandro Vallejo wrote:
>>> --- a/xen/arch/x86/Kconfig.cpu
>>> +++ b/xen/arch/x86/Kconfig.cpu
>>> @@ -19,4 +19,47 @@ config INTEL
>>> May be turned off in builds targetting other vendors. Otherwise,
>>> must be enabled for Xen to work suitably on Intel platforms.
>>>
>>> +config HYGON
>>> + bool "Support Hygon CPUs"
>>> + select AMD
>>> + default y
>>> + help
>>> + Detection, tunings and quirks for Hygon platforms.
>>> +
>>> + May be turned off in builds targetting other vendors. Otherwise,
>>> + must be enabled for Xen to work suitably on Hygon platforms.
>>> +
>>> +
>>> +config CENTAUR
>>> + bool "Support Centaur CPUs"
>>> + select INTEL
>>> + default y
>>> + help
>>> + Detection, tunings and quirks for Centaur platforms.
>>> +
>>> + May be turned off in builds targetting other vendors. Otherwise,
>>> + must be enabled for Xen to work suitably on Centaur platforms.
>>> +
>>> +config SHANGHAI
>>> + bool "Support Shanghai CPUs"
>>> + select INTEL
>>> + default y
>>> + help
>>> + Detection, tunings and quirks for Shanghai platforms.
>>> +
>>> + May be turned off in builds targetting other vendors. Otherwise,
>>> + must be enabled for Xen to work suitably on Shanghai platforms.
>>> +
>>> +config UNKNOWN_CPU_VENDOR
>>> + bool "Support unknown CPU vendors"
>>> + default y
>>> + help
>>> + This option prevents a panic on boot when the host CPU vendor isn't
>>> + supported by going into a legacy compatibility mode and not applying
>>> + any relevant tunings or quirks.
>>> +
>>> + Not selecting this options while selecting multiple vendors doesn't
>>> have
>>> + any major effect on code size, but selecting a single vendor with this
>>> + option cleared produces a much smaller build.
>>
>> Shouldn't this option's prompt be suppressed when all other vendors were
>> selected off? Else the degenerate case can result that I mentioned in
>> reply to patch 03.
>
> You mean having the option disappear when any explicit vendor is enabled?
No, I mean the prompt (not the option) to disappear when _no_ explicit
vendor is enabled. Because of the select-s above, that could effectively
be as simple as
config UNKNOWN_CPU_VENDOR
bool "Support unknown CPU vendors" if INTEL || AMD
default y
Otherwise, as indicated, the conditional around the panic() in patch 03
degenerates: The panic() would be skipped despite UNKNOWN_CPU_VENDOR=n,
as with X86_ENABLED_VENDORS being 0, cpu_vendor() can't tell
UNKNOWN_CPU_VENDOR=n from UNKNOWN_CPU_VENDOR=y.
Jan
