QEMU maps certain regions into the guest multiple times, as seen in the
trace below. Currently the MSHV kernel driver will reject those
mappings. To workaround this, a record is kept (a static global list of
"slots", inspired by what the HVF accelerator has implemented). An
overlapping region is not registered at the hypervisor, and marked as
mapped=false. If there is an UNMAPPED_GPA exit, we can look for a slot
that is unmapped and would cover the GPA. In this case we map out the
conflicting slot and map in the requested region.
mshv_set_phys_mem add=1 name=pc.bios
mshv_map_memory => u_a=7ffff4e00000 gpa=00fffc0000 size=00040000
mshv_set_phys_mem add=1 name=ioapic
mshv_set_phys_mem add=1 name=hpet
mshv_set_phys_mem add=0 name=pc.ram
mshv_unmap_memory u_a=7fff67e00000 gpa=0000000000 size=80000000
mshv_set_phys_mem add=1 name=pc.ram
mshv_map_memory u_a=7fff67e00000 gpa=0000000000 size=000c0000
mshv_set_phys_mem add=1 name=pc.rom
mshv_map_memory u_a=7ffff4c00000 gpa=00000c0000 size=00020000
mshv_set_phys_mem add=1 name=pc.bios
mshv_remap_attempt => u_a=7ffff4e20000 gpa=00000e0000 size=00020000
The mapping table is guarded by a mutex for concurrent modification and
RCU mechanisms for concurrent reads. Writes occur rarely, but we'll have
to verify whether an unmapped region exist for each UNMAPPED_GPA exit,
which happens frequently.
Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250916164847.77883-24-magnuskulke@linux.microsoft.com
[Fix format strings for trace-events; mshv.h/mshv_int.h split. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
efc4093358