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authorNitesh Narayan Lal <nitesh@redhat.com>2019-11-07 15:53:43 +0300
committerPaolo Bonzini <pbonzini@redhat.com>2019-11-15 13:44:22 +0300
commit7ee30bc132c683d06a6d9e360e39e483e3990708 (patch)
treee458eb18be9b81b7cc08e297abb113f3ee923441 /arch/x86/kvm/ioapic.c
parent8750e72a79dda2f665ce17b62049f4d62130d991 (diff)
downloadlinux-7ee30bc132c683d06a6d9e360e39e483e3990708.tar.xz
KVM: x86: deliver KVM IOAPIC scan request to target vCPUs
In IOAPIC fixed delivery mode instead of flushing the scan requests to all vCPUs, we should only send the requests to vCPUs specified within the destination field. This patch introduces kvm_get_dest_vcpus_mask() API which retrieves an array of target vCPUs by using kvm_apic_map_get_dest_lapic() and then based on the vcpus_idx, it sets the bit in a bitmap. However, if the above fails kvm_get_dest_vcpus_mask() finds the target vCPUs by traversing all available vCPUs. Followed by setting the bits in the bitmap. If we had different vCPUs in the previous request for the same redirection table entry then bits corresponding to these vCPUs are also set. This to done to keep ioapic_handled_vectors synchronized. This bitmap is then eventually passed on to kvm_make_vcpus_request_mask() to generate a masked request only for the target vCPUs. This would enable us to reduce the latency overhead on isolated vCPUs caused by the IPI to process due to KVM_REQ_IOAPIC_SCAN. Suggested-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/ioapic.c')
-rw-r--r--arch/x86/kvm/ioapic.c33
1 files changed, 31 insertions, 2 deletions
diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index d859ae8890d0..ce30ef23c86b 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -271,8 +271,9 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
{
unsigned index;
bool mask_before, mask_after;
- int old_remote_irr, old_delivery_status;
union kvm_ioapic_redirect_entry *e;
+ unsigned long vcpu_bitmap;
+ int old_remote_irr, old_delivery_status, old_dest_id, old_dest_mode;
switch (ioapic->ioregsel) {
case IOAPIC_REG_VERSION:
@@ -296,6 +297,8 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
/* Preserve read-only fields */
old_remote_irr = e->fields.remote_irr;
old_delivery_status = e->fields.delivery_status;
+ old_dest_id = e->fields.dest_id;
+ old_dest_mode = e->fields.dest_mode;
if (ioapic->ioregsel & 1) {
e->bits &= 0xffffffff;
e->bits |= (u64) val << 32;
@@ -321,7 +324,33 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
if (e->fields.trig_mode == IOAPIC_LEVEL_TRIG
&& ioapic->irr & (1 << index))
ioapic_service(ioapic, index, false);
- kvm_make_scan_ioapic_request(ioapic->kvm);
+ if (e->fields.delivery_mode == APIC_DM_FIXED) {
+ struct kvm_lapic_irq irq;
+
+ irq.shorthand = 0;
+ irq.vector = e->fields.vector;
+ irq.delivery_mode = e->fields.delivery_mode << 8;
+ irq.dest_id = e->fields.dest_id;
+ irq.dest_mode = e->fields.dest_mode;
+ kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq,
+ &vcpu_bitmap);
+ if (old_dest_mode != e->fields.dest_mode ||
+ old_dest_id != e->fields.dest_id) {
+ /*
+ * Update vcpu_bitmap with vcpus specified in
+ * the previous request as well. This is done to
+ * keep ioapic_handled_vectors synchronized.
+ */
+ irq.dest_id = old_dest_id;
+ irq.dest_mode = old_dest_mode;
+ kvm_bitmap_or_dest_vcpus(ioapic->kvm, &irq,
+ &vcpu_bitmap);
+ }
+ kvm_make_scan_ioapic_request_mask(ioapic->kvm,
+ &vcpu_bitmap);
+ } else {
+ kvm_make_scan_ioapic_request(ioapic->kvm);
+ }
break;
}
}