KVM: Add dirty-ring-size property

Add a parameter for dirty gfn count for dirty rings.  If zero, dirty ring is
disabled.  Otherwise dirty ring will be enabled with the per-vcpu gfn count as
specified.  If dirty ring cannot be enabled due to unsupported kernel or
illegal parameter, it'll fallback to dirty logging.

By default, dirty ring is not enabled (dirty-gfn-count default to 0).

Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <20210506160549.130416-9-peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Peter Xu 2021-05-06 12:05:47 -04:00 committed by Paolo Bonzini
parent 563d32ba9b
commit 2ea5cb0a47
2 changed files with 58 additions and 0 deletions

View File

@ -126,6 +126,8 @@ struct KVMState
KVMMemoryListener *ml;
AddressSpace *as;
} *as;
uint64_t kvm_dirty_ring_bytes; /* Size of the per-vcpu dirty ring */
uint32_t kvm_dirty_ring_size; /* Number of dirty GFNs per ring */
};
KVMState *kvm_state;
@ -3182,6 +3184,42 @@ bool kvm_kernel_irqchip_split(void)
return kvm_state->kernel_irqchip_split == ON_OFF_AUTO_ON;
}
static void kvm_get_dirty_ring_size(Object *obj, Visitor *v,
const char *name, void *opaque,
Error **errp)
{
KVMState *s = KVM_STATE(obj);
uint32_t value = s->kvm_dirty_ring_size;
visit_type_uint32(v, name, &value, errp);
}
static void kvm_set_dirty_ring_size(Object *obj, Visitor *v,
const char *name, void *opaque,
Error **errp)
{
KVMState *s = KVM_STATE(obj);
Error *error = NULL;
uint32_t value;
if (s->fd != -1) {
error_setg(errp, "Cannot set properties after the accelerator has been initialized");
return;
}
visit_type_uint32(v, name, &value, &error);
if (error) {
error_propagate(errp, error);
return;
}
if (value & (value - 1)) {
error_setg(errp, "dirty-ring-size must be a power of two.");
return;
}
s->kvm_dirty_ring_size = value;
}
static void kvm_accel_instance_init(Object *obj)
{
KVMState *s = KVM_STATE(obj);
@ -3191,6 +3229,8 @@ static void kvm_accel_instance_init(Object *obj)
s->kvm_shadow_mem = -1;
s->kernel_irqchip_allowed = true;
s->kernel_irqchip_split = ON_OFF_AUTO_AUTO;
/* KVM dirty ring is by default off */
s->kvm_dirty_ring_size = 0;
}
static void kvm_accel_class_init(ObjectClass *oc, void *data)
@ -3212,6 +3252,12 @@ static void kvm_accel_class_init(ObjectClass *oc, void *data)
NULL, NULL);
object_class_property_set_description(oc, "kvm-shadow-mem",
"KVM shadow MMU size");
object_class_property_add(oc, "dirty-ring-size", "uint32",
kvm_get_dirty_ring_size, kvm_set_dirty_ring_size,
NULL, NULL);
object_class_property_set_description(oc, "dirty-ring-size",
"Size of KVM dirty page ring buffer (default: 0, i.e. use bitmap)");
}
static const TypeInfo kvm_accel_type = {

View File

@ -141,6 +141,7 @@ DEF("accel", HAS_ARG, QEMU_OPTION_accel,
" kvm-shadow-mem=size of KVM shadow MMU in bytes\n"
" split-wx=on|off (enable TCG split w^x mapping)\n"
" tb-size=n (TCG translation block cache size)\n"
" dirty-ring-size=n (KVM dirty ring GFN count, default 0)\n"
" thread=single|multi (enable multi-threaded TCG)\n", QEMU_ARCH_ALL)
SRST
``-accel name[,prop=value[,...]]``
@ -181,6 +182,17 @@ SRST
where both the back-end and front-ends support it and no
incompatible TCG features have been enabled (e.g.
icount/replay).
``dirty-ring-size=n``
When the KVM accelerator is used, it controls the size of the per-vCPU
dirty page ring buffer (number of entries for each vCPU). It should
be a value that is power of two, and it should be 1024 or bigger (but
still less than the maximum value that the kernel supports). 4096
could be a good initial value if you have no idea which is the best.
Set this value to 0 to disable the feature. By default, this feature
is disabled (dirty-ring-size=0). When enabled, KVM will instead
record dirty pages in a bitmap.
ERST
DEF("smp", HAS_ARG, QEMU_OPTION_smp,