[PATCH 3/4] kvm/host: fix paravirt clocksource to be compatible with xen.

Gerd Hoffmann
2008-04-24T08:37:07Z

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
arch/x86/kvm/x86.c | 63 +++++++++++++++++++++++++++++++++++++++++++--------
1 files changed, 53 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0ce5563..45b71c6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -493,7 +493,7 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
{
static int version;
struct kvm_wall_clock wc;
- struct timespec wc_ts;
+ struct timespec now,sys,boot;

if (!wall_clock)
return;
@@ -502,9 +502,16 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)

kvm_write_guest(kvm, wall_clock, &version, sizeof(version));

- wc_ts = current_kernel_time();
- wc.wc_sec = wc_ts.tv_sec;
- wc.wc_nsec = wc_ts.tv_nsec;
+#if 0
+ /* Hmm, getboottime() isn't exported to modules ... */
+ getboottime(&boot);
+#else
+ now = current_kernel_time();
+ ktime_get_ts(&sys);
+ boot = ns_to_timespec(timespec_to_ns(&now) - timespec_to_ns(&sys));
+#endif
+ wc.wc_sec = boot.tv_sec;
+ wc.wc_nsec = boot.tv_nsec;
wc.wc_version = version;

kvm_write_guest(kvm, wall_clock, &wc, sizeof(wc));
@@ -537,20 +544,58 @@ static void kvm_write_guest_time(struct kvm_vcpu *v)
/*
* The interface expects us to write an even number signaling that the
* update is finished. Since the guest won't see the intermediate
- * state, we just write "2" at the end
+ * state, we just increase by 2 at the end.
*/
- vcpu->hv_clock.version = 2;
+ vcpu->hv_clock.version += 2;

shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);

memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
- sizeof(vcpu->hv_clock));
+ sizeof(vcpu->hv_clock));

kunmap_atomic(shared_kaddr, KM_USER0);

mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);
}

+static uint32_t div_frac(uint32_t dividend, uint32_t divisor)
+{
+ uint32_t quotient, remainder;
+
+ __asm__ ( "divl %4"
+ : "=a" (quotient), "=d" (remainder)
+ : "0" (0), "1" (dividend), "r" (divisor) );
+ return quotient;
+}
+
+static void kvm_set_time_scale(uint32_t tsc_khz, struct kvm_vcpu_time_info *hv_clock)
+{
+ uint64_t nsecs = 1000000000LL;
+ int32_t shift = 0;
+ uint64_t tps64;
+ uint32_t tps32;
+
+ tps64 = tsc_khz * 1000LL;
+ while (tps64 > nsecs*2) {
+ tps64 >>= 1;
+ shift--;
+ }
+
+ tps32 = (uint32_t)tps64;
+ while (tps32 <= (uint32_t)nsecs) {
+ tps32 <<= 1;
+ shift++;
+ }
+
+ hv_clock->tsc_shift = shift;
+ hv_clock->tsc_to_system_mul = div_frac(nsecs, tps32);
+
+#if 0
+ printk(KERN_DEBUG "%s: tsc_khz %u, tsc_shift %d, tsc_mul %u\n",
+ __FUNCTION__, tsc_khz, hv_clock->tsc_shift,
+ hv_clock->tsc_to_system_mul);
+#endif
+}

int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
@@ -599,9 +644,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
/* ...but clean it before doing the actual write */
vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);

- vcpu->arch.hv_clock.tsc_to_system_mul =
- clocksource_khz2mult(tsc_khz, 22);
- vcpu->arch.hv_clock.tsc_shift = 22;
+ kvm_set_time_scale(tsc_khz, &vcpu->arch.hv_clock);

down_read(&current->mm->mmap_sem);
vcpu->arch.time_page =
--
1.5.4.1