mirrors/linux
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git synced 2025-12-27 14:41:22 -05:00
Code Issues Packages Projects Releases Wiki Activity

KVM: x86: Trigger I/O APIC route rescan in kvm_arch_irq_routing_update()

Browse Source 
Trigger the I/O APIC route rescan that's performed for a split IRQ chip
after userspace updates IRQ routes in kvm_arch_irq_routing_update(), i.e.
before dropping kvm->irq_lock.  Calling kvm_make_all_cpus_request() under
a mutex is perfectly safe, and the smp_wmb()+smp_mb__after_atomic() pair
in __kvm_make_request()+kvm_check_request() ensures the new routing is
visible to vCPUs prior to the request being visible to vCPUs.

In all likelihood, commit b053b2aef2 ("KVM: x86: Add EOI exit bitmap
inference") somewhat arbitrarily made the request outside of irq_lock to
avoid holding irq_lock any longer than is strictly necessary.  And then
commit abdb080f7a ("kvm/irqchip: kvm_arch_irq_routing_update renaming
split") took the easy route of adding another arch hook instead of risking
a functional change.

Note, the call to synchronize_srcu_expedited() does NOT provide ordering
guarantees with respect to vCPUs scanning the new routing; as above, the
request infrastructure provides the necessary ordering.  I.e. there's no
need to wait for kvm_scan_ioapic_routes() to complete if it's actively
running, because regardless of whether it grabs the old or new table, the
vCPU will have another KVM_REQ_SCAN_IOAPIC pending, i.e. will rescan again
and see the new mappings.

Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20250611213557.294358-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson
2025-06-11 14:35:40 -07:00
parent 23b54381ce
commit e295d2e7fb
3 changed files with 3 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
arch/x86/kvm/irq_comm.c
View File

@@ -395,13 +395,6 @@ int kvm_setup_default_irq_routing(struct kvm *kvm)
ARRAY_SIZE(default_routing), 0);
}
void kvm_arch_post_irq_routing_update(struct kvm *kvm)
{
if (!irqchip_split(kvm))
return;
kvm_make_scan_ioapic_request(kvm);
}
void kvm_scan_ioapic_irq(struct kvm_vcpu *vcpu, u32 dest_id, u16 dest_mode,
u8 vector, unsigned long *ioapic_handled_vectors)
{
@@ -466,4 +459,7 @@ void kvm_arch_irq_routing_update(struct kvm *kvm)
#ifdef CONFIG_KVM_HYPERV
kvm_hv_irq_routing_update(kvm);
#endif
if (irqchip_split(kvm))
kvm_make_scan_ioapic_request(kvm);
}

4
include/linux/kvm_host.h
View File

@@ -1024,14 +1024,10 @@ void vcpu_put(struct kvm_vcpu *vcpu);
#ifdef __KVM_HAVE_IOAPIC
void kvm_arch_post_irq_ack_notifier_list_update(struct kvm *kvm);
void kvm_arch_post_irq_routing_update(struct kvm *kvm);
#else
static inline void kvm_arch_post_irq_ack_notifier_list_update(struct kvm *kvm)
{
}
static inline void kvm_arch_post_irq_routing_update(struct kvm *kvm)
{
}
#endif
#ifdef CONFIG_HAVE_KVM_IRQCHIP

2
virt/kvm/irqchip.c
View File

@@ -222,8 +222,6 @@ int kvm_set_irq_routing(struct kvm *kvm,
kvm_arch_irq_routing_update(kvm);
mutex_unlock(&kvm->irq_lock);
kvm_arch_post_irq_routing_update(kvm);
synchronize_srcu_expedited(&kvm->irq_srcu);
new = old;