[PATCH v3 03/62] KVM: Pass new routing entries and irqfd when updating IRTEs

Sean Christopherson
2025-06-11T22:47:01Z

When updating IRTEs in response to a GSI routing or IRQ bypass change,
pass the new/current routing information along with the associated irqfd.
This will allow KVM x86 to harden, simplify, and deduplicate its code.

Since adding/removing a bypass producer is now conveniently protected with
irqfds.lock, i.e. can't run concurrently with kvm_irq_routing_update(),
use the routing information cached in the irqfd instead of looking up
the information in the current GSI routing tables.

Opportunistically convert an existing printk() to pr_info() and put its
string onto a single line (old code that strictly adhered to 80 chars).

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/arm64/kvm/arm.c | 7 ++++---
arch/x86/include/asm/kvm_host.h | 6 ++++--
arch/x86/kvm/svm/avic.c | 18 +++++++----------
arch/x86/kvm/svm/svm.h | 5 +++--
arch/x86/kvm/vmx/posted_intr.c | 19 ++++++++---------
arch/x86/kvm/vmx/posted_intr.h | 8 ++++++--
arch/x86/kvm/x86.c | 36 ++++++++++++++++++---------------
include/linux/kvm_host.h | 7 +++++--
virt/kvm/eventfd.c | 11 +++++-----
9 files changed, 62 insertions(+), 55 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 38a91bb5d4c7..a9a39e0375f7 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2771,8 +2771,9 @@ bool kvm_arch_irqfd_route_changed(struct kvm_kernel_irq_routing_entry *old,
return memcmp(&old->msi, &new->msi, sizeof(new->msi));
}

-int kvm_arch_update_irqfd_routing(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set)
+int kvm_arch_update_irqfd_routing(struct kvm_kernel_irqfd *irqfd,
+ struct kvm_kernel_irq_routing_entry *old,
+ struct kvm_kernel_irq_routing_entry *new)
{
/*
* Remapping the vLPI requires taking the its_lock mutex to resolve
@@ -2781,7 +2782,7 @@ int kvm_arch_update_irqfd_routing(struct kvm *kvm, unsigned int host_irq,
*
* Unmap the vLPI and fall back to software LPI injection.
*/
- return kvm_vgic_v4_unset_forwarding(kvm, host_irq);
+ return kvm_vgic_v4_unset_forwarding(irqfd->kvm, irqfd->producer->irq);
}

void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *cons)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 21ccb122ab76..2a6ef1398da7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -296,6 +296,7 @@ enum x86_intercept_stage;
*/
#define KVM_APIC_PV_EOI_PENDING 1

+struct kvm_kernel_irqfd;
struct kvm_kernel_irq_routing_entry;

/*
@@ -1844,8 +1845,9 @@ struct kvm_x86_ops {
void (*vcpu_blocking)(struct kvm_vcpu *vcpu);
void (*vcpu_unblocking)(struct kvm_vcpu *vcpu);

- int (*pi_update_irte)(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set);
+ int (*pi_update_irte)(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
+ unsigned int host_irq, uint32_t guest_irq,
+ struct kvm_kernel_irq_routing_entry *new);
void (*pi_start_assignment)(struct kvm *kvm);
void (*apicv_pre_state_restore)(struct kvm_vcpu *vcpu);
void (*apicv_post_state_restore)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 7338879d1c0c..adacf00d6664 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -18,6 +18,7 @@
#include <linux/hashtable.h>
#include <linux/amd-iommu.h>
#include <linux/kvm_host.h>
+#include <linux/kvm_irqfd.h>

#include <asm/irq_remapping.h>

@@ -885,21 +886,14 @@ get_pi_vcpu_info(struct kvm *kvm, struct kvm_kernel_irq_routing_entry *e,
return 0;
}

-/*
- * avic_pi_update_irte - set IRTE for Posted-Interrupts
- *
- * @kvm: kvm
- * @host_irq: host irq of the interrupt
- * @guest_irq: gsi of the interrupt
- * @set: set or unset PI
- * returns 0 on success, < 0 on failure
- */
-int avic_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set)
+int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
+ unsigned int host_irq, uint32_t guest_irq,
+ struct kvm_kernel_irq_routing_entry *new)
{
struct kvm_kernel_irq_routing_entry *e;
struct kvm_irq_routing_table *irq_rt;
bool enable_remapped_mode = true;
+ bool set = !!new;
int idx, ret = 0;

if (!kvm_arch_has_assigned_device(kvm) || !kvm_arch_has_irq_bypass())
@@ -925,6 +919,8 @@ int avic_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
if (e->type != KVM_IRQ_ROUTING_MSI)
continue;

+ WARN_ON_ONCE(new && memcmp(e, new, sizeof(*new)));
+
/**
* Here, we setup with legacy mode in the following cases:
* 1. When cannot target interrupt to a specific vcpu.
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index e6f3c6a153a0..b35fce30d923 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -736,8 +736,9 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
void avic_vcpu_put(struct kvm_vcpu *vcpu);
void avic_apicv_post_state_restore(struct kvm_vcpu *vcpu);
void avic_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu);
-int avic_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set);
+int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
+ unsigned int host_irq, uint32_t guest_irq,
+ struct kvm_kernel_irq_routing_entry *new);
void avic_vcpu_blocking(struct kvm_vcpu *vcpu);
void avic_vcpu_unblocking(struct kvm_vcpu *vcpu);
void avic_ring_doorbell(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
index 5c615e5845bf..110fb19848ab 100644
--- a/arch/x86/kvm/vmx/posted_intr.c
+++ b/arch/x86/kvm/vmx/posted_intr.c
@@ -2,6 +2,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kvm_host.h>
+#include <linux/kvm_irqfd.h>

#include <asm/irq_remapping.h>
#include <asm/cpu.h>
@@ -294,17 +295,9 @@ void vmx_pi_start_assignment(struct kvm *kvm)
kvm_make_all_cpus_request(kvm, KVM_REQ_UNBLOCK);
}

-/*
- * vmx_pi_update_irte - set IRTE for Posted-Interrupts
- *
- * @kvm: kvm
- * @host_irq: host irq of the interrupt
- * @guest_irq: gsi of the interrupt
- * @set: set or unset PI
- * returns 0 on success, < 0 on failure
- */
-int vmx_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set)
+int vmx_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
+ unsigned int host_irq, uint32_t guest_irq,
+ struct kvm_kernel_irq_routing_entry *new)
{
struct kvm_kernel_irq_routing_entry *e;
struct kvm_irq_routing_table *irq_rt;
@@ -312,6 +305,7 @@ int vmx_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
struct kvm_lapic_irq irq;
struct kvm_vcpu *vcpu;
struct vcpu_data vcpu_info;
+ bool set = !!new;
int idx, ret = 0;

if (!vmx_can_use_vtd_pi(kvm))
@@ -329,6 +323,9 @@ int vmx_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
hlist_for_each_entry(e, &irq_rt->map[guest_irq], link) {
if (e->type != KVM_IRQ_ROUTING_MSI)
continue;
+
+ WARN_ON_ONCE(new && memcmp(e, new, sizeof(*new)));
+
/*
* VT-d PI cannot support posting multicast/broadcast
* interrupts to a vCPU, we still use interrupt remapping
diff --git a/arch/x86/kvm/vmx/posted_intr.h b/arch/x86/kvm/vmx/posted_intr.h
index 80499ea0e674..a94afcb55f7f 100644
--- a/arch/x86/kvm/vmx/posted_intr.h
+++ b/arch/x86/kvm/vmx/posted_intr.h
@@ -3,6 +3,9 @@
#define __KVM_X86_VMX_POSTED_INTR_H

#include <linux/bitmap.h>
+#include <linux/find.h>
+#include <linux/kvm_host.h>
+
#include <asm/posted_intr.h>

void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu);
@@ -11,8 +14,9 @@ void pi_wakeup_handler(void);
void __init pi_init_cpu(int cpu);
void pi_apicv_pre_state_restore(struct kvm_vcpu *vcpu);
bool pi_has_pending_interrupt(struct kvm_vcpu *vcpu);
-int vmx_pi_update_irte(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set);
+int vmx_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm,
+ unsigned int host_irq, uint32_t guest_irq,
+ struct kvm_kernel_irq_routing_entry *new);
void vmx_pi_start_assignment(struct kvm *kvm);

static inline int pi_find_highest_vector(struct pi_desc *pi_desc)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 28a20f0aa3dd..93711a5ef272 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13507,31 +13507,31 @@ int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons,
struct kvm_kernel_irqfd *irqfd =
container_of(cons, struct kvm_kernel_irqfd, consumer);
struct kvm *kvm = irqfd->kvm;
- int ret;
+ int ret = 0;

kvm_arch_start_assignment(irqfd->kvm);

spin_lock_irq(&kvm->irqfds.lock);
irqfd->producer = prod;

- ret = kvm_x86_call(pi_update_irte)(irqfd->kvm,
- prod->irq, irqfd->gsi, 1);
- if (ret)
- kvm_arch_end_assignment(irqfd->kvm);
-
+ if (irqfd->irq_entry.type == KVM_IRQ_ROUTING_MSI) {
+ ret = kvm_x86_call(pi_update_irte)(irqfd, irqfd->kvm, prod->irq,
+ irqfd->gsi, &irqfd->irq_entry);
+ if (ret)
+ kvm_arch_end_assignment(irqfd->kvm);
+ }
spin_unlock_irq(&kvm->irqfds.lock);

-
return ret;
}

void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
struct irq_bypass_producer *prod)
{
- int ret;
struct kvm_kernel_irqfd *irqfd =
container_of(cons, struct kvm_kernel_irqfd, consumer);
struct kvm *kvm = irqfd->kvm;
+ int ret;

WARN_ON(irqfd->producer != prod);

@@ -13544,11 +13544,13 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
spin_lock_irq(&kvm->irqfds.lock);
irqfd->producer = NULL;

- ret = kvm_x86_call(pi_update_irte)(irqfd->kvm,
- prod->irq, irqfd->gsi, 0);
- if (ret)
- printk(KERN_INFO "irq bypass consumer (token %p) unregistration"
- " fails: %d\n", irqfd->consumer.token, ret);
+ if (irqfd->irq_entry.type == KVM_IRQ_ROUTING_MSI) {
+ ret = kvm_x86_call(pi_update_irte)(irqfd, irqfd->kvm, prod->irq,
+ irqfd->gsi, NULL);
+ if (ret)
+ pr_info("irq bypass consumer (token %p) unregistration fails: %d\n",
+ irqfd->consumer.token, ret);
+ }

spin_unlock_irq(&kvm->irqfds.lock);

@@ -13556,10 +13558,12 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
kvm_arch_end_assignment(irqfd->kvm);
}

-int kvm_arch_update_irqfd_routing(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set)
+int kvm_arch_update_irqfd_routing(struct kvm_kernel_irqfd *irqfd,
+ struct kvm_kernel_irq_routing_entry *old,
+ struct kvm_kernel_irq_routing_entry *new)
{
- return kvm_x86_call(pi_update_irte)(kvm, host_irq, guest_irq, set);
+ return kvm_x86_call(pi_update_irte)(irqfd, irqfd->kvm, irqfd->producer->irq,
+ irqfd->gsi, new);
}

bool kvm_arch_irqfd_route_changed(struct kvm_kernel_irq_routing_entry *old,
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3b5575d0b574..a4160c1c0c6b 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2401,6 +2401,8 @@ struct kvm_vcpu *kvm_get_running_vcpu(void);
struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);

#if IS_ENABLED(CONFIG_HAVE_KVM_IRQ_BYPASS)
+struct kvm_kernel_irqfd;
+
bool kvm_arch_has_irq_bypass(void);
int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *,
struct irq_bypass_producer *);
@@ -2408,8 +2410,9 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *,
struct irq_bypass_producer *);
void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *);
void kvm_arch_irq_bypass_start(struct irq_bypass_consumer *);
-int kvm_arch_update_irqfd_routing(struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set);
+int kvm_arch_update_irqfd_routing(struct kvm_kernel_irqfd *irqfd,
+ struct kvm_kernel_irq_routing_entry *old,
+ struct kvm_kernel_irq_routing_entry *new);
bool kvm_arch_irqfd_route_changed(struct kvm_kernel_irq_routing_entry *,
struct kvm_kernel_irq_routing_entry *);
#endif /* CONFIG_HAVE_KVM_IRQ_BYPASS */
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 11e5d1e3f12e..85581550dc8d 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -285,9 +285,9 @@ void __attribute__((weak)) kvm_arch_irq_bypass_start(
{
}

-int __attribute__((weak)) kvm_arch_update_irqfd_routing(
- struct kvm *kvm, unsigned int host_irq,
- uint32_t guest_irq, bool set)
+int __weak kvm_arch_update_irqfd_routing(struct kvm_kernel_irqfd *irqfd,
+ struct kvm_kernel_irq_routing_entry *old,
+ struct kvm_kernel_irq_routing_entry *new)
{
return 0;
}
@@ -619,9 +619,8 @@ void kvm_irq_routing_update(struct kvm *kvm)
#if IS_ENABLED(CONFIG_HAVE_KVM_IRQ_BYPASS)
if (irqfd->producer &&
kvm_arch_irqfd_route_changed(&old, &irqfd->irq_entry)) {
- int ret = kvm_arch_update_irqfd_routing(
- irqfd->kvm, irqfd->producer->irq,
- irqfd->gsi, 1);
+ int ret = kvm_arch_update_irqfd_routing(irqfd, &old, &irqfd->irq_entry);
+
WARN_ON(ret);
}
#endif
--
2.50.0.rc1.591.g9c95f17f64-goog