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authorMarcelo Tosatti <mtosatti@redhat.com>2008-12-11 20:45:05 +0100
committerAvi Kivity <avi@redhat.com>2009-03-24 11:02:53 +0200
commit53f658b3c33616a4997ee254311b335e59063289 (patch)
treefbef1e51bfa096dd28a00b2449d567f2c3ab6fb9 /arch/x86/kvm
parente8c4a4e8a7cc047dfb3c26b2cbc8599ad3460364 (diff)
KVM: VMX: initialize TSC offset relative to vm creation time
VMX initializes the TSC offset for each vcpu at different times, and also reinitializes it for vcpus other than 0 on APIC SIPI message. This bug causes the TSC's to appear unsynchronized in the guest, even if the host is good. Older Linux kernels don't handle the situation very well, so gettimeofday is likely to go backwards in time: http://www.mail-archive.com/kvm@vger.kernel.org/msg02955.html http://sourceforge.net/tracker/index.php?func=detail&aid=2025534&group_id=180599&atid=893831 Fix it by initializating the offset of each vcpu relative to vm creation time, and moving it from vmx_vcpu_reset to vmx_vcpu_setup, out of the APIC MP init path. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
-rw-r--r--arch/x86/kvm/vmx.c19
-rw-r--r--arch/x86/kvm/x86.c2
2 files changed, 13 insertions, 8 deletions
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index cee81c9a665..3312047664a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -865,11 +865,8 @@ static u64 guest_read_tsc(void)
* writes 'guest_tsc' into guest's timestamp counter "register"
* guest_tsc = host_tsc + tsc_offset ==> tsc_offset = guest_tsc - host_tsc
*/
-static void guest_write_tsc(u64 guest_tsc)
+static void guest_write_tsc(u64 guest_tsc, u64 host_tsc)
{
- u64 host_tsc;
-
- rdtscll(host_tsc);
vmcs_write64(TSC_OFFSET, guest_tsc - host_tsc);
}
@@ -934,6 +931,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
struct kvm_msr_entry *msr;
+ u64 host_tsc;
int ret = 0;
switch (msr_index) {
@@ -959,7 +957,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
vmcs_writel(GUEST_SYSENTER_ESP, data);
break;
case MSR_IA32_TIME_STAMP_COUNTER:
- guest_write_tsc(data);
+ rdtscll(host_tsc);
+ guest_write_tsc(data, host_tsc);
break;
case MSR_P6_PERFCTR0:
case MSR_P6_PERFCTR1:
@@ -2109,7 +2108,7 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
{
u32 host_sysenter_cs, msr_low, msr_high;
u32 junk;
- u64 host_pat;
+ u64 host_pat, tsc_this, tsc_base;
unsigned long a;
struct descriptor_table dt;
int i;
@@ -2237,6 +2236,12 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
vmcs_writel(CR0_GUEST_HOST_MASK, ~0UL);
vmcs_writel(CR4_GUEST_HOST_MASK, KVM_GUEST_CR4_MASK);
+ tsc_base = vmx->vcpu.kvm->arch.vm_init_tsc;
+ rdtscll(tsc_this);
+ if (tsc_this < vmx->vcpu.kvm->arch.vm_init_tsc)
+ tsc_base = tsc_this;
+
+ guest_write_tsc(0, tsc_base);
return 0;
}
@@ -2328,8 +2333,6 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
vmcs_write32(GUEST_INTERRUPTIBILITY_INFO, 0);
vmcs_write32(GUEST_PENDING_DBG_EXCEPTIONS, 0);
- guest_write_tsc(0);
-
/* Special registers */
vmcs_write64(GUEST_IA32_DEBUGCTL, 0);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 873602b5edf..3b2acfd72d7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4170,6 +4170,8 @@ struct kvm *kvm_arch_create_vm(void)
/* Reserve bit 0 of irq_sources_bitmap for userspace irq source */
set_bit(KVM_USERSPACE_IRQ_SOURCE_ID, &kvm->arch.irq_sources_bitmap);
+ rdtscll(kvm->arch.vm_init_tsc);
+
return kvm;
}