@@ -3763,6 +3763,7 @@ static void kvm_accel_instance_init(Object *obj)
/* KVM dirty ring is by default off */
s->kvm_dirty_ring_size = 0;
s->kvm_dirty_ring_with_bitmap = false;
+ s->kvm_eager_split_size = 0;
s->notify_vmexit = NOTIFY_VMEXIT_OPTION_RUN;
s->notify_window = 0;
s->xen_version = 0;
@@ -116,6 +116,7 @@ struct KVMState
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 */
bool kvm_dirty_ring_with_bitmap;
+ uint64_t kvm_eager_split_size; /* Eager Page Splitting chunk size */
struct KVMDirtyRingReaper reaper;
NotifyVmexitOption notify_vmexit;
uint32_t notify_window;
@@ -186,6 +186,7 @@ DEF("accel", HAS_ARG, QEMU_OPTION_accel,
" 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"
+ " eager-split-size=n (KVM Eager Page Split chunk size, default 0, disabled. ARM only)\n"
" notify-vmexit=run|internal-error|disable,notify-window=n (enable notify VM exit and set notify window, x86 only)\n"
" thread=single|multi (enable multi-threaded TCG)\n", QEMU_ARCH_ALL)
SRST
@@ -244,6 +245,20 @@ SRST
is disabled (dirty-ring-size=0). When enabled, KVM will instead
record dirty pages in a bitmap.
+ ``eager-split-size=n``
+ KVM implements dirty page logging at the PAGE_SIZE granularity and
+ enabling dirty-logging on a huge-page requires breaking it into
+ PAGE_SIZE pages in the first place. KVM on ARM does this splitting
+ lazily by default. There are performance benefits in doing huge-page
+ split eagerly, especially in situations where TLBI costs associated
+ with break-before-make sequences are considerable and also if guest
+ workloads are read intensive. The size here specifies how many pages
+ to break at a time and needs to be a valid block size which is
+ 1GB/2MB/4KB, 32MB/16KB and 512MB/64KB for 4KB/16KB/64KB PAGE_SIZE
+ respectively. Be wary of specifying a higher size as it will have an
+ impact on the memory. By default, this feature is disabled
+ (eager-split-size=0).
+
``notify-vmexit=run|internal-error|disable,notify-window=n``
Enables or disables notify VM exit support on x86 host and specify
the corresponding notify window to trigger the VM exit if enabled.
@@ -30,6 +30,7 @@
#include "exec/address-spaces.h"
#include "hw/boards.h"
#include "hw/irq.h"
+#include "qapi/visitor.h"
#include "qemu/log.h"
const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
@@ -287,6 +288,26 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
}
}
+ if (s->kvm_eager_split_size) {
+ uint32_t sizes;
+
+ sizes = kvm_vm_check_extension(s, KVM_CAP_ARM_SUPPORTED_BLOCK_SIZES);
+ if (!sizes) {
+ s->kvm_eager_split_size = 0;
+ warn_report("Eager Page Split support not available");
+ } else if (!(s->kvm_eager_split_size & sizes)) {
+ error_report("Eager Page Split requested chunk size not valid");
+ ret = -EINVAL;
+ } else {
+ ret = kvm_vm_enable_cap(s, KVM_CAP_ARM_EAGER_SPLIT_CHUNK_SIZE, 0,
+ s->kvm_eager_split_size);
+ if (ret < 0) {
+ error_report("Enabling of Eager Page Split failed: %s",
+ strerror(-ret));
+ }
+ }
+ }
+
kvm_arm_init_debug(s);
return ret;
@@ -1069,6 +1090,46 @@ bool kvm_arch_cpu_check_are_resettable(void)
return true;
}
+static void kvm_arch_get_eager_split_size(Object *obj, Visitor *v,
+ const char *name, void *opaque,
+ Error **errp)
+{
+ KVMState *s = KVM_STATE(obj);
+ uint64_t value = s->kvm_eager_split_size;
+
+ visit_type_size(v, name, &value, errp);
+}
+
+static void kvm_arch_set_eager_split_size(Object *obj, Visitor *v,
+ const char *name, void *opaque,
+ Error **errp)
+{
+ KVMState *s = KVM_STATE(obj);
+ uint64_t value;
+
+ if (s->fd != -1) {
+ error_setg(errp, "Unable to set early-split-size after KVM has been initialized");
+ return;
+ }
+
+ if (!visit_type_size(v, name, &value, errp)) {
+ return;
+ }
+
+ if (value && !is_power_of_2(value)) {
+ error_setg(errp, "early-split-size must be a power of two");
+ return;
+ }
+
+ s->kvm_eager_split_size = value;
+}
+
void kvm_arch_accel_class_init(ObjectClass *oc)
{
+ object_class_property_add(oc, "eager-split-size", "size",
+ kvm_arch_get_eager_split_size,
+ kvm_arch_set_eager_split_size, NULL, NULL);
+
+ object_class_property_set_description(oc, "eager-split-size",
+ "Eager Page Split chunk size for hugepages. (default: 0, disabled)");
}