Re: [PATCH v2] generic/altp2m: align and simplify altp2m_vcpu_idx()

On 09.07.2026 17:23, Dmytro Prokopchuk1 wrote:
> The return type of altp2m_vcpu_idx() in the generic altp2m.h header is
> currently 'unsigned int', which is inconsistent with its uint16_t
> return type on x86 and the altp2m_idx member of the monitor structures.
> 
> To fix this type inconsistency and simplify the header, this patch
> replaces the static inline implementation of altp2m_vcpu_idx()
> (contained a BUG() stub) with a simple function declaration returning
> uint16_t.

While I appreciate that this may be the easiest route, I disagree. Not
even considering ./CODING_STYLE, uint16_t may be an appropriate choice
on x86, but it pretty certainly isn't a good one in generic code. I
have a vague recollection that it might actually have been me to request
use of unsigned int when the stub was added. If so, it was for said
reason.

> For architectures using the generic altp2m.h header (such as ARM when
> CONFIG_VM_EVENT is enabled), common code calls to altp2m_vcpu_idx() in
> common/monitor.c are guarded by altp2m_active(), which statically
> returns false. The compiler DCE will optimize out these calls, avoiding
> any linker issues for the missing definition.

This part is definitely fine in principle. However, if a declaration
suffices, that would then better also be what x86 uses when !ALTP2M.
I.e. I think you want to #include <asm-generic/altp2m.h> from that
section of x86'es asm/altp2m.h

Jan