This helps a lot on modern kernels where Linux is much more finicky
about using the TSC as a time source.
Regards,
Anthony Liguori
Subject: [PATCH] KVM: paravirt time source
Author: Anthony Liguori <[EMAIL PROTECTED]>
This patch implements a paravirtual time source based on a new field added to
the VMCA. The host provides time in nanoseconds to the guest.
Signed-off-by: Anthony Liguori <[EMAIL PROTECTED]>
diff --git a/arch/i386/kernel/kvm.c b/arch/i386/kernel/kvm.c
index 22ea647..62c3b5b 100644
--- a/arch/i386/kernel/kvm.c
+++ b/arch/i386/kernel/kvm.c
@@ -26,6 +26,18 @@
#include <linux/cpu.h>
#include <linux/mm.h>
+#include <linux/clocksource.h>
+#include <linux/workqueue.h>
+#include <linux/cpufreq.h>
+#include <linux/jiffies.h>
+#include <linux/init.h>
+#include <linux/dmi.h>
+#include <linux/acpi_pmtmr.h>
+
+#include "mach_timer.h"
+
+#define KVM_SCALE 22
+
struct kvm_paravirt_state
{
struct kvm_vmca *vmca;
@@ -38,6 +50,7 @@ struct kvm_paravirt_state
static DEFINE_PER_CPU(struct kvm_paravirt_state *, paravirt_state);
static int do_nop_io_delay;
+static int do_paravirt_clock;
static u64 msr_set_vmca;
static long kvm_hypercall(unsigned int nr, unsigned long p1,
@@ -62,6 +75,28 @@ static long kvm_hypercall(unsigned int nr, unsigned long p1,
return ret;
}
+static cycle_t kvm_clocksource_read(void)
+{
+ struct kvm_paravirt_state *state = get_cpu_var(paravirt_state);
+ cycle_t ret;
+
+ kvm_hypercall(KVM_HYPERCALL_UPDATE_TIME, 0, 0, 0, 0);
+ ret = state->vmca->real_nsecs;
+ put_cpu_var(paravirt_state);
+
+ return ret;
+}
+
+static struct clocksource clocksource_kvm = {
+ .name = "kvm",
+ .rating = 200,
+ .read = kvm_clocksource_read,
+ .mask = CLOCKSOURCE_MASK(64),
+ .mult = 1 << KVM_SCALE,
+ .shift = KVM_SCALE,
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
/*
* No need for any "IO delay" on KVM
*/
@@ -76,6 +111,14 @@ static void paravirt_ops_setup(void)
if (do_nop_io_delay)
paravirt_ops.io_delay = kvm_io_delay;
+ if (do_paravirt_clock) {
+ int err;
+
+ err = clocksource_register(&clocksource_kvm);
+ WARN_ON(err);
+ printk(KERN_INFO "KVM: using paravirt clock source\n");
+ }
+
paravirt_ops.paravirt_enabled = 1;
apply_paravirt(__parainstructions, __parainstructions_end);
@@ -114,6 +157,9 @@ static int paravirt_initialize(void)
if ((edx & KVM_FEATURE_NOP_IO_DELAY))
do_nop_io_delay = 1;
+ if ((edx & KVM_FEATURE_PARAVIRT_CLOCK))
+ do_paravirt_clock = 1;
+
on_each_cpu(paravirt_activate, NULL, 0, 1);
return 0;
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 1369310..e455fca 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -44,6 +44,7 @@
#include <linux/cpumask.h>
#include <linux/smp.h>
#include <linux/kvm_para.h>
+#include <linux/delay.h>
#include "x86_emulate.h"
#include "segment_descriptor.h"
@@ -93,7 +94,8 @@ struct vfsmount *kvmfs_mnt;
#define EFER_RESERVED_BITS 0xfffffffffffff2fe
#define KVM_PARAVIRT_FEATURES \
- (KVM_FEATURE_VMCA | KVM_FEATURE_NOP_IO_DELAY)
+ (KVM_FEATURE_VMCA | KVM_FEATURE_NOP_IO_DELAY | \
+ KVM_FEATURE_PARAVIRT_CLOCK)
#define KVM_MSR_SET_VMCA 0x87655678
@@ -1346,10 +1348,34 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_emulate_halt);
+static int kvm_hypercall_update_time(struct kvm_vcpu *vcpu)
+{
+ struct kvm_vmca *vmca;
+ struct timespec now;
+
+ if (unlikely(!vcpu->para_state_page))
+ return -KVM_EINVAL;
+
+ ktime_get_ts(&now);
+
+ vmca = kmap(vcpu->para_state_page);
+
+ vmca->real_nsecs = now.tv_nsec + now.tv_sec * (cycles_t)1e9;
+
+ mark_page_dirty(vcpu->kvm, vcpu->para_state_gpa >> PAGE_SHIFT);
+ kunmap(vcpu->para_state_page);
+
+ return 0;
+}
+
static int dispatch_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
unsigned long p1, unsigned long p2,
unsigned long p3, unsigned long p4)
{
+ switch (nr) {
+ case KVM_HYPERCALL_UPDATE_TIME:
+ return kvm_hypercall_update_time(vcpu);
+ }
return -KVM_ENOSYS;
}
diff --git a/include/linux/kvm_para.h b/include/linux/kvm_para.h
index 11ebad8..4f27fb1 100644
--- a/include/linux/kvm_para.h
+++ b/include/linux/kvm_para.h
@@ -15,10 +15,12 @@
#define KVM_FEATURE_VMCA (1UL << 0)
#define KVM_FEATURE_NOP_IO_DELAY (1UL << 1)
+#define KVM_FEATURE_PARAVIRT_CLOCK (1UL << 2)
struct kvm_vmca
{
u64 hypercall_gpa;
+ u64 real_nsecs;
};
/*
@@ -33,5 +35,8 @@ struct kvm_vmca
*/
#define KVM_ENOSYS ENOSYS
+#define KVM_EINVAL EINVAL
+
+#define KVM_HYPERCALL_UPDATE_TIME 0
#endif
-------------------------------------------------------------------------
This SF.net email is sponsored by DB2 Express
Download DB2 Express C - the FREE version of DB2 express and take
control of your XML. No limits. Just data. Click to get it now.
http://sourceforge.net/powerbar/db2/
_______________________________________________
kvm-devel mailing list
kvm-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/kvm-devel
