+linux-um
On Wed, 2025-05-07 at 18:40 +0000, tip-bot2 for Ingo Molnar wrote:
>
> To resolve these kinds of problems and to allow <asm/tsc.h> to be included on
> UML,
> add a simplified version of <asm/tsc.h>, which only adds the rdtsc()
> definition.
OK, weird, why would that be needed - UM isn't really X86.
> arch/um/include/asm/tsc.h | 25 +++++++++++++++++++++++++
Feels that should be in arch/x86/um/asm/ instead, which I believe is
also included but then at least pretends to keep the notion that UML
could be ported to other architectures ;-)
> +static __always_inline u64 rdtsc(void)
> +{
> + EAX_EDX_DECLARE_ARGS(val, low, high);
> +
> + asm volatile("rdtsc" : EAX_EDX_RET(val, low, high));
> +
> + return EAX_EDX_VAL(val, low, high);
> +}
Though I also wonder where this is called at all that would be relevant
for UML? If it's not then perhaps we should just make using it
unbuildable, a la
u64 __um_has_no_rdtsc(void);
#define rdtsc() __um_has_no_rdtsc()
or something like that... (and then of course keep it in the current
location). But looking at the 0-day report that'd probably break
building the driver on UML; while the driver doesn't seem important we
wouldn't really want that...
Actually, that's just because of the stupid quirk in UML/X86:
config DRM_ACCEL_HABANALABS
tristate "HabanaLabs AI accelerators"
depends on DRM_ACCEL
depends on X86_64
that last line should almost certainly be "depends on X86 && X86_64"
because ARCH=um will set UM and X86_64, but not X86 since the arch
Kconfig symbols are X86 and UM respectively, but the UML subarch still
selects X86_64 ...
I dunno. I guess we can put rdtsc() into UML on x86 as I suggested about
the file placement, or we can also just fix the Kconfig there.
johannes
