On 01/09/2025 9:33 am, Jan Beulich wrote:
> On 29.08.2025 18:17, Andrew Cooper wrote:
>> This is a port of Linux commit 517234446c1a ("x86/apic: Get rid of
>> get_physical_broadcast()") to Xen. Thomas Gleixner notes:
>>
>> There is no point for this function. The only case where this is used is
>> when there is no XAPIC available, which means the broadcast address is 0xF.
>>
>> In Linux, users of get_physical_broadcast() have already been hidden behind
>> CONFIG_X86_32 suggesting we can drop all of this, but that's a task for some
>> other time.
>>
>> In Xen as with Linux, setup_ioapic_ids_from_mpc() and io_apic_get_unique_id()
>> are only called in pre-xAPIC cases, so can use a broadcast ID of 0xf. The
>> only other user is __print_IO_APIC() for diagnostics, which can simply drop
>> the check.
> For setup_ioapic_ids_from_mpc() in Linux that's partly because it gained an
> Intel && !APIC_XAPIC() check which we don't have.
In Xen, setup_ioapic_ids_from_mpc() has a comment and an xAPIC check at
the start of the function.
We're lacking Linux commit a38c5380ef9f "x86: io_apic: Split
setup_ioapic_ids_from_mpc()" which moved the check to the caller.
Perhaps I should s/called/used/ in the commit message?
~Andrew
