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linux/virt/kvm/irqchip.c
Yi Wang fbe4a7e881 KVM: Setup empty IRQ routing when creating a VM
Setup empty IRQ routing during VM creation so that x86 and s390 don't need
to set empty/dummy IRQ routing during KVM_CREATE_IRQCHIP (in future
patches).  Initializing IRQ routing before there are any potential readers
allows KVM to avoid the synchronize_srcu() in kvm_set_irq_routing(), which
can introduces 20+ milliseconds of latency in the VM creation path.

Ensuring that all VMs have non-NULL IRQ routing also hardens KVM against
misbehaving userspace VMMs, e.g. RISC-V dynamically instantiates its
interrupt controller, but doesn't override kvm_arch_intc_initialized() or
kvm_arch_irqfd_allowed(), and so can likely reach kvm_irq_map_gsi()
without fully initialized IRQ routing.

Signed-off-by: Yi Wang <foxywang@tencent.com>
Acked-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Link: https://lore.kernel.org/r/20240506101751.3145407-2-foxywang@tencent.com
[sean: init refcount after IRQ routing, fix stub, massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
2024-06-11 14:18:34 -07:00

264 lines
6.1 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* irqchip.c: Common API for in kernel interrupt controllers
* Copyright (c) 2007, Intel Corporation.
* Copyright 2010 Red Hat, Inc. and/or its affiliates.
* Copyright (c) 2013, Alexander Graf <agraf@suse.de>
*
* This file is derived from virt/kvm/irq_comm.c.
*
* Authors:
* Yaozu (Eddie) Dong <Eddie.dong@intel.com>
* Alexander Graf <agraf@suse.de>
*/
#include <linux/kvm_host.h>
#include <linux/slab.h>
#include <linux/srcu.h>
#include <linux/export.h>
#include <trace/events/kvm.h>
int kvm_irq_map_gsi(struct kvm *kvm,
struct kvm_kernel_irq_routing_entry *entries, int gsi)
{
struct kvm_irq_routing_table *irq_rt;
struct kvm_kernel_irq_routing_entry *e;
int n = 0;
irq_rt = srcu_dereference_check(kvm->irq_routing, &kvm->irq_srcu,
lockdep_is_held(&kvm->irq_lock));
if (irq_rt && gsi < irq_rt->nr_rt_entries) {
hlist_for_each_entry(e, &irq_rt->map[gsi], link) {
entries[n] = *e;
++n;
}
}
return n;
}
int kvm_irq_map_chip_pin(struct kvm *kvm, unsigned irqchip, unsigned pin)
{
struct kvm_irq_routing_table *irq_rt;
irq_rt = srcu_dereference(kvm->irq_routing, &kvm->irq_srcu);
return irq_rt->chip[irqchip][pin];
}
int kvm_send_userspace_msi(struct kvm *kvm, struct kvm_msi *msi)
{
struct kvm_kernel_irq_routing_entry route;
if (!kvm_arch_irqchip_in_kernel(kvm) || (msi->flags & ~KVM_MSI_VALID_DEVID))
return -EINVAL;
route.msi.address_lo = msi->address_lo;
route.msi.address_hi = msi->address_hi;
route.msi.data = msi->data;
route.msi.flags = msi->flags;
route.msi.devid = msi->devid;
return kvm_set_msi(&route, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1, false);
}
/*
* Return value:
* < 0 Interrupt was ignored (masked or not delivered for other reasons)
* = 0 Interrupt was coalesced (previous irq is still pending)
* > 0 Number of CPUs interrupt was delivered to
*/
int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level,
bool line_status)
{
struct kvm_kernel_irq_routing_entry irq_set[KVM_NR_IRQCHIPS];
int ret = -1, i, idx;
trace_kvm_set_irq(irq, level, irq_source_id);
/* Not possible to detect if the guest uses the PIC or the
* IOAPIC. So set the bit in both. The guest will ignore
* writes to the unused one.
*/
idx = srcu_read_lock(&kvm->irq_srcu);
i = kvm_irq_map_gsi(kvm, irq_set, irq);
srcu_read_unlock(&kvm->irq_srcu, idx);
while (i--) {
int r;
r = irq_set[i].set(&irq_set[i], kvm, irq_source_id, level,
line_status);
if (r < 0)
continue;
ret = r + ((ret < 0) ? 0 : ret);
}
return ret;
}
static void free_irq_routing_table(struct kvm_irq_routing_table *rt)
{
int i;
if (!rt)
return;
for (i = 0; i < rt->nr_rt_entries; ++i) {
struct kvm_kernel_irq_routing_entry *e;
struct hlist_node *n;
hlist_for_each_entry_safe(e, n, &rt->map[i], link) {
hlist_del(&e->link);
kfree(e);
}
}
kfree(rt);
}
void kvm_free_irq_routing(struct kvm *kvm)
{
/* Called only during vm destruction. Nobody can use the pointer
at this stage */
struct kvm_irq_routing_table *rt = rcu_access_pointer(kvm->irq_routing);
free_irq_routing_table(rt);
}
static int setup_routing_entry(struct kvm *kvm,
struct kvm_irq_routing_table *rt,
struct kvm_kernel_irq_routing_entry *e,
const struct kvm_irq_routing_entry *ue)
{
struct kvm_kernel_irq_routing_entry *ei;
int r;
u32 gsi = array_index_nospec(ue->gsi, KVM_MAX_IRQ_ROUTES);
/*
* Do not allow GSI to be mapped to the same irqchip more than once.
* Allow only one to one mapping between GSI and non-irqchip routing.
*/
hlist_for_each_entry(ei, &rt->map[gsi], link)
if (ei->type != KVM_IRQ_ROUTING_IRQCHIP ||
ue->type != KVM_IRQ_ROUTING_IRQCHIP ||
ue->u.irqchip.irqchip == ei->irqchip.irqchip)
return -EINVAL;
e->gsi = gsi;
e->type = ue->type;
r = kvm_set_routing_entry(kvm, e, ue);
if (r)
return r;
if (e->type == KVM_IRQ_ROUTING_IRQCHIP)
rt->chip[e->irqchip.irqchip][e->irqchip.pin] = e->gsi;
hlist_add_head(&e->link, &rt->map[e->gsi]);
return 0;
}
void __attribute__((weak)) kvm_arch_irq_routing_update(struct kvm *kvm)
{
}
bool __weak kvm_arch_can_set_irq_routing(struct kvm *kvm)
{
return true;
}
int kvm_set_irq_routing(struct kvm *kvm,
const struct kvm_irq_routing_entry *ue,
unsigned nr,
unsigned flags)
{
struct kvm_irq_routing_table *new, *old;
struct kvm_kernel_irq_routing_entry *e;
u32 i, j, nr_rt_entries = 0;
int r;
for (i = 0; i < nr; ++i) {
if (ue[i].gsi >= KVM_MAX_IRQ_ROUTES)
return -EINVAL;
nr_rt_entries = max(nr_rt_entries, ue[i].gsi);
}
nr_rt_entries += 1;
new = kzalloc(struct_size(new, map, nr_rt_entries), GFP_KERNEL_ACCOUNT);
if (!new)
return -ENOMEM;
new->nr_rt_entries = nr_rt_entries;
for (i = 0; i < KVM_NR_IRQCHIPS; i++)
for (j = 0; j < KVM_IRQCHIP_NUM_PINS; j++)
new->chip[i][j] = -1;
for (i = 0; i < nr; ++i) {
r = -ENOMEM;
e = kzalloc(sizeof(*e), GFP_KERNEL_ACCOUNT);
if (!e)
goto out;
r = -EINVAL;
switch (ue->type) {
case KVM_IRQ_ROUTING_MSI:
if (ue->flags & ~KVM_MSI_VALID_DEVID)
goto free_entry;
break;
default:
if (ue->flags)
goto free_entry;
break;
}
r = setup_routing_entry(kvm, new, e, ue);
if (r)
goto free_entry;
++ue;
}
mutex_lock(&kvm->irq_lock);
old = rcu_dereference_protected(kvm->irq_routing, 1);
rcu_assign_pointer(kvm->irq_routing, new);
kvm_irq_routing_update(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;
r = 0;
goto out;
free_entry:
kfree(e);
out:
free_irq_routing_table(new);
return r;
}
/*
* Allocate empty IRQ routing by default so that additional setup isn't needed
* when userspace-driven IRQ routing is activated, and so that kvm->irq_routing
* is guaranteed to be non-NULL.
*/
int kvm_init_irq_routing(struct kvm *kvm)
{
struct kvm_irq_routing_table *new;
int chip_size;
new = kzalloc(struct_size(new, map, 1), GFP_KERNEL_ACCOUNT);
if (!new)
return -ENOMEM;
new->nr_rt_entries = 1;
chip_size = sizeof(int) * KVM_NR_IRQCHIPS * KVM_IRQCHIP_NUM_PINS;
memset(new->chip, -1, chip_size);
RCU_INIT_POINTER(kvm->irq_routing, new);
return 0;
}