motorhead/qemu
1
0
Fork 0
mirror of https://github.com/Motorhead1991/qemu.git synced 2025-08-04 08:13:54 -06:00
Code Issues Projects Releases Packages Wiki Activity Actions

target/i386: Support up to 32768 CPUs without IRQ remapping

Browse source 
The IOAPIC has an 'Extended Destination ID' field in its RTE, which maps
to bits 11-4 of the MSI address. Since those address bits fall within a
given 4KiB page they were historically non-trivial to use on real hardware.

The Intel IOMMU uses the lowest bit to indicate a remappable format MSI,
and then the remaining 7 bits are part of the index.

Where the remappable format bit isn't set, we can actually use the other
seven to allow external (IOAPIC and MSI) interrupts to reach up to 32768
CPUs instead of just the 255 permitted on bare metal.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <78097f9218300e63e751e077a0a5ca029b56ba46.camel@infradead.org>
[Fix UBSAN warning. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
This commit is contained in:
David Woodhouse 2020-10-05 15:18:19 +01:00 • committed by Paolo Bonzini
parent 75b208c283
commit c1bb5418e3
6 changed files with 79 additions and 31 deletions
Download patch file Download diff file Expand all files Collapse all files

1
include/standard-headers/asm-x86/kvm_para.h
View file

@ -32,6 +32,7 @@
#define KVM_FEATURE_POLL_CONTROL 12
#define KVM_FEATURE_PV_SCHED_YIELD 13
#define KVM_FEATURE_ASYNC_PF_INT 14
#define KVM_FEATURE_MSI_EXT_DEST_ID 15
#define KVM_HINTS_REALTIME 0