cloud-hypervisor/arch
Thomas Barrett 5c0b66529a arch: x86_64: handle npot CPU topology
This PR addresses a bug in which the cpu topology of a guest
with non power-of-two number of cores is incorrect. For example,
in some contexts, a virtual machine with 2-sockets and 12-cores
will incorrectly believe that 16 cores are on socket 1 and 8
cores are on socket 2. In other cases, common topology enumeration
software such as hwloc will crash.

The root of the problem was the way that cloud-hypervisor generates
apic_id. On x86_64, the (x2) apic_id embeds information about cpu
topology. The cpuid instruction is primarily used to discover the
number of sockets, dies, cores, threads, etc. Using this information,
the (x2) apic_id is masked to determine which {core, die, socket} the
cpu is on. When the cpu topology is not a power of two
(e.g. a 12-core machine), this requires non-contiguous (x2) apic_id.

Signed-off-by: Thomas Barrett <tbarrett@crusoeenergy.com>
2024-01-01 10:05:03 +00:00
..
src arch: x86_64: handle npot CPU topology 2024-01-01 10:05:03 +00:00
Cargo.toml build: Bump thiserror from 1.0.40 to 1.0.52 2023-12-30 10:28:17 +00:00