From: Leonid Shatz <leonid.shatz@xxxxxxxxxx>
Since commit e79f245ddec1 ("X86/KVM: Properly update 'tsc_offset' to
represent the running guest"), vcpu->arch.tsc_offset meaning was
changed to always reflect the tsc_offset value set on active VMCS.
Regardless if vCPU is currently running L1 or L2.
However, above mentioned commit failed to also change
kvm_vcpu_write_tsc_offset() to set vcpu->arch.tsc_offset correctly.
This is because vmx_write_tsc_offset() could set the tsc_offset value
in active VMCS to given offset parameter *plus vmcs12->tsc_offset*.
However, kvm_vcpu_write_tsc_offset() just sets vcpu->arch.tsc_offset
to given offset parameter. Without taking into account the possible
addition of vmcs12->tsc_offset. (Same is true for SVM case).
Fix this issue by changing kvm_x86_ops->write_tsc_offset() to return
actually set tsc_offset in active VMCS and modify
kvm_vcpu_write_tsc_offset() to set returned value in
vcpu->arch.tsc_offset.
In addition, rename write_tsc_offset() argument to clearly indicate
it specifies a L1 TSC offset.
Fixes: e79f245ddec1 ("X86/KVM: Properly update 'tsc_offset' to represent the running guest")
Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx>
Reviewed-by: Mihai Carabas <mihai.carabas@xxxxxxxxxx>
Reviewed-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Signed-off-by: Leonid Shatz <leonid.shatz@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 6 +++++-
arch/x86/kvm/svm.c | 9 +++++----
arch/x86/kvm/vmx.c | 21 +++++++++------------
arch/x86/kvm/x86.c | 8 ++++----
4 files changed, 23 insertions(+), 21 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 55e51ff7e421..cc9df79b1016 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1094,7 +1094,11 @@ struct kvm_x86_ops {
bool (*has_wbinvd_exit)(void);
u64 (*read_l1_tsc_offset)(struct kvm_vcpu *vcpu);
- void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
+ /*
+ * Updates active guest TSC offset based on given L1 TSC offset
+ * and returns actual TSC offset set for the active guest
+ */
+ u64 (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 l1_offset);
void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 0e21ccc46792..842d4bb053d1 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1446,7 +1446,7 @@ static u64 svm_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
return vcpu->arch.tsc_offset;
}
-static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
+static u64 svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 l1_offset)
{
struct vcpu_svm *svm = to_svm(vcpu);
u64 g_tsc_offset = 0;
@@ -1455,15 +1455,16 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
/* Write L1's TSC offset. */
g_tsc_offset = svm->vmcb->control.tsc_offset -
svm->nested.hsave->control.tsc_offset;
- svm->nested.hsave->control.tsc_offset = offset;
+ svm->nested.hsave->control.tsc_offset = l1_offset;
} else
trace_kvm_write_tsc_offset(vcpu->vcpu_id,
svm->vmcb->control.tsc_offset,
- offset);
+ l1_offset);
- svm->vmcb->control.tsc_offset = offset + g_tsc_offset;
+ svm->vmcb->control.tsc_offset = l1_offset + g_tsc_offset;
mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
+ return svm->vmcb->control.tsc_offset;
}
static void avic_init_vmcb(struct vcpu_svm *svm)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4555077d69ce..20d90ebd6cc8 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3452,11 +3452,9 @@ static u64 vmx_read_l1_tsc_offset(struct kvm_vcpu *vcpu)
return vcpu->arch.tsc_offset;
}
-/*
- * writes 'offset' into guest's timestamp counter offset register
- */
-static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
+static u64 vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 l1_offset)
{
+ u64 active_offset = l1_offset;
if (is_guest_mode(vcpu)) {
/*
* We're here if L1 chose not to trap WRMSR to TSC. According
@@ -3464,17 +3462,16 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
* set for L2 remains unchanged, and still needs to be added
* to the newly set TSC to get L2's TSC.
*/
- struct vmcs12 *vmcs12;
- /* recalculate vmcs02.TSC_OFFSET: */
- vmcs12 = get_vmcs12(vcpu);
- vmcs_write64(TSC_OFFSET, offset +
- (nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETING) ?
- vmcs12->tsc_offset : 0));
+ struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+ if (nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETING))
+ active_offset += vmcs12->tsc_offset;
} else {
trace_kvm_write_tsc_offset(vcpu->vcpu_id,
- vmcs_read64(TSC_OFFSET), offset);
- vmcs_write64(TSC_OFFSET, offset);
+ vmcs_read64(TSC_OFFSET), l1_offset);
}
+
+ vmcs_write64(TSC_OFFSET, active_offset);
+ return active_offset;
}
/*
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8525dc75a79a..c4e80af1a54e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1766,10 +1766,9 @@ u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
}
EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
-static void kvm_vcpu_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
+static void kvm_vcpu_write_tsc_offset(struct kvm_vcpu *vcpu, u64 l1_offset)
{
- kvm_x86_ops->write_tsc_offset(vcpu, offset);
- vcpu->arch.tsc_offset = offset;
+ vcpu->arch.tsc_offset = kvm_x86_ops->write_tsc_offset(vcpu, l1_offset);
}
static inline bool kvm_check_tsc_unstable(void)
@@ -1897,7 +1896,8 @@ EXPORT_SYMBOL_GPL(kvm_write_tsc);
static inline void adjust_tsc_offset_guest(struct kvm_vcpu *vcpu,
s64 adjustment)
{
- kvm_vcpu_write_tsc_offset(vcpu, vcpu->arch.tsc_offset + adjustment);
+ u64 l1_tsc_offset = kvm_x86_ops->read_l1_tsc_offset(vcpu);
+ kvm_vcpu_write_tsc_offset(vcpu, l1_tsc_offset + adjustment);
}
static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
--
2.16.1
