kvm/i386: Add xen-evtchn-max-pirq property

The default number of PIRQs is set to 256 to avoid issues with 32-bit MSI
devices. Allow it to be increased if the user desires.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
This commit is contained in:
David Woodhouse 2023-01-18 14:36:23 +00:00
parent 6096cf7877
commit e16aff4cc2
6 changed files with 54 additions and 10 deletions

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@ -3705,6 +3705,7 @@ static void kvm_accel_instance_init(Object *obj)
s->notify_window = 0;
s->xen_version = 0;
s->xen_gnttab_max_frames = 64;
s->xen_evtchn_max_pirq = 256;
}
/**

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@ -302,17 +302,18 @@ void xen_evtchn_create(void)
}
/*
* We could parameterise the number of PIRQs available if needed,
* but for now limit it to 256. The Xen scheme for encoding PIRQ#
* into an MSI message is not compatible with 32-bit MSI, as it
* puts the high bits of the PIRQ# into the high bits of the MSI
* message address, instead of using the Extended Destination ID
* in address bits 4-11 which perhaps would have been a better
* choice. So to keep life simple, just stick with 256 as the
* default, which conveniently doesn't need to set anything
* outside the low 32 bits of the address.
* The Xen scheme for encoding PIRQ# into an MSI message is not
* compatible with 32-bit MSI, as it puts the high bits of the
* PIRQ# into the high bits of the MSI message address, instead of
* using the Extended Destination ID in address bits 4-11 which
* perhaps would have been a better choice.
*
* To keep life simple, kvm_accel_instance_init() initialises the
* default to 256. which conveniently doesn't need to set anything
* outside the low 32 bits of the address. It can be increased by
* setting the xen-evtchn-max-pirq property.
*/
s->nr_pirqs = 256;
s->nr_pirqs = kvm_xen_get_evtchn_max_pirq();
s->nr_pirq_inuse_words = DIV_ROUND_UP(s->nr_pirqs, 64);
s->pirq_inuse_bitmap = g_new0(uint64_t, s->nr_pirq_inuse_words);

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@ -121,6 +121,7 @@ struct KVMState
uint32_t xen_version;
uint32_t xen_caps;
uint16_t xen_gnttab_max_frames;
uint16_t xen_evtchn_max_pirq;
};
void kvm_memory_listener_register(KVMState *s, KVMMemoryListener *kml,

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@ -26,6 +26,7 @@ void kvm_xen_inject_vcpu_callback_vector(uint32_t vcpu_id, int type);
void kvm_xen_set_callback_asserted(void);
int kvm_xen_set_vcpu_virq(uint32_t vcpu_id, uint16_t virq, uint16_t port);
uint16_t kvm_xen_get_gnttab_max_frames(void);
uint16_t kvm_xen_get_evtchn_max_pirq(void);
#define kvm_xen_has_cap(cap) (!!(kvm_xen_get_caps() & \
KVM_XEN_HVM_CONFIG_ ## cap))

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@ -5922,6 +5922,33 @@ static void kvm_arch_set_xen_gnttab_max_frames(Object *obj, Visitor *v,
s->xen_gnttab_max_frames = value;
}
static void kvm_arch_get_xen_evtchn_max_pirq(Object *obj, Visitor *v,
const char *name, void *opaque,
Error **errp)
{
KVMState *s = KVM_STATE(obj);
uint16_t value = s->xen_evtchn_max_pirq;
visit_type_uint16(v, name, &value, errp);
}
static void kvm_arch_set_xen_evtchn_max_pirq(Object *obj, Visitor *v,
const char *name, void *opaque,
Error **errp)
{
KVMState *s = KVM_STATE(obj);
Error *error = NULL;
uint16_t value;
visit_type_uint16(v, name, &value, &error);
if (error) {
error_propagate(errp, error);
return;
}
s->xen_evtchn_max_pirq = value;
}
void kvm_arch_accel_class_init(ObjectClass *oc)
{
object_class_property_add_enum(oc, "notify-vmexit", "NotifyVMexitOption",
@ -5954,6 +5981,13 @@ void kvm_arch_accel_class_init(ObjectClass *oc)
NULL, NULL);
object_class_property_set_description(oc, "xen-gnttab-max-frames",
"Maximum number of grant table frames");
object_class_property_add(oc, "xen-evtchn-max-pirq", "uint16",
kvm_arch_get_xen_evtchn_max_pirq,
kvm_arch_set_xen_evtchn_max_pirq,
NULL, NULL);
object_class_property_set_description(oc, "xen-evtchn-max-pirq",
"Maximum number of Xen PIRQs");
}
void kvm_set_max_apic_id(uint32_t max_apic_id)

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@ -1765,6 +1765,12 @@ uint16_t kvm_xen_get_gnttab_max_frames(void)
return s->xen_gnttab_max_frames;
}
uint16_t kvm_xen_get_evtchn_max_pirq(void)
{
KVMState *s = KVM_STATE(current_accel());
return s->xen_evtchn_max_pirq;
}
int kvm_put_xen_state(CPUState *cs)
{
X86CPU *cpu = X86_CPU(cs);