Fwd: [KVM TSC emulation 6/9] Allow adjust_tsc_offset to be in host or guest cycles

Fwd: [KVM TSC emulation 6/9] Allow adjust_tsc_offset to be in host or guest cycles

[Zachary Amsden]

-------- Original Message --------
Subject: 	[KVM TSC emulation 6/9] Allow adjust_tsc_offset to be in host 
or guest cycles
Date: 	Mon, 20 Jun 2011 16:59:34 -0700
From: 	Zachary Amsden <zamsden@redhat.com>
To: 	Avi Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, 
Glauber Costa <glommer@redhat.com>, Frank Arnold <farnold@redhat.com>, 
Joerg Roedel <joerg.roedel@amd.com>, Jan Kiszka 
<jan.kiszka@siemens.com>, linux-kvm@vger.kernel.org, 
linux-kernel@vger.kernel.org, Zachary Amsden <zamsden@gmail.com>, Avi 
Kivity <avi@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, Glauber 
Costa <glommer@redhat.com>, Frank Arnold <farnold@redhat.com>, Joerg 
Roedel <joerg.roedel@amd.com>, Jan Kiszka <jan.kiszka@siemens.com>, 
linux-kvm@vger.kernel.org
CC: 	Zachary Amsden <zamsden@redhat.com>, Zachary Amsden 
<zamsden@gmail.com>



Redefine the API to take a parameter indicating whether an
adjustment is in host or guest cycles.

Signed-off-by: Zachary Amsden<zamsden@redhat.com>
---
  arch/x86/include/asm/kvm_host.h |   13 ++++++++++++-
  arch/x86/kvm/svm.c              |    6 +++++-
  arch/x86/kvm/vmx.c              |    2 +-
  arch/x86/kvm/x86.c              |    2 +-
  4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 3b9fdb5..c2854da 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -599,7 +599,7 @@ struct kvm_x86_ops {
  	u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
  	int (*get_lpage_level)(void);
  	bool (*rdtscp_supported)(void);
-	void (*adjust_tsc_offset)(struct kvm_vcpu *vcpu, s64 adjustment);
+	void (*adjust_tsc_offset)(struct kvm_vcpu *vcpu, s64 adjustment, bool host);

  	void (*set_tdp_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);

@@ -630,6 +630,17 @@ struct kvm_arch_async_pf {

  extern struct kvm_x86_ops *kvm_x86_ops;

+static inline void adjust_tsc_offset_guest(struct kvm_vcpu *vcpu,
+					   s64 adjustment)
+{
+	kvm_x86_ops->adjust_tsc_offset(vcpu, adjustment, false);
+}
+
+static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
+{
+	kvm_x86_ops->adjust_tsc_offset(vcpu, adjustment, true);
+}
+
  int kvm_mmu_module_init(void);
  void kvm_mmu_module_exit(void);

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 47f557e..dcab00e 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -957,10 +957,14 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
  	mark_dirty(svm->vmcb, VMCB_INTERCEPTS);
  }

-static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
+static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool host)
  {
  	struct vcpu_svm *svm = to_svm(vcpu);

+	WARN_ON(adjustment<  0);
+	if (host)
+		adjustment = svm_scale_tsc(vcpu, adjustment);
+
  	svm->vmcb->control.tsc_offset += adjustment;
  	if (is_guest_mode(vcpu))
  		svm->nested.hsave->control.tsc_offset += adjustment;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index bc3ecfd..780fe12 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1782,7 +1782,7 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
  			to_vmx(vcpu)->nested.vmcs01_tsc_offset;
  }

-static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
+static void vmx_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool host)
  {
  	u64 offset = vmcs_read64(TSC_OFFSET);
  	vmcs_write64(TSC_OFFSET, offset + adjustment);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8fe988a..10950f7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1125,7 +1125,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
  	if (vcpu->tsc_catchup) {
  		u64 tsc = compute_guest_tsc(v, kernel_ns);
  		if (tsc>  tsc_timestamp) {
-			kvm_x86_ops->adjust_tsc_offset(v, tsc - tsc_timestamp);
+			adjust_tsc_offset_guest(v, tsc - tsc_timestamp);
  			tsc_timestamp = tsc;
  		}
  	}
-- 
1.7.1

Re: Fwd: [KVM TSC emulation 6/9] Allow adjust_tsc_offset to be in host or guest cycles

[Joerg Roedel]

On Tue, Jun 21, 2011 at 05:22:29AM -0700, Zachary Amsden wrote:
> -static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment)
> +static void svm_adjust_tsc_offset(struct kvm_vcpu *vcpu, s64 adjustment, bool host)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>
> +	WARN_ON(adjustment<  0);
> +	if (host)
> +		adjustment = svm_scale_tsc(vcpu, adjustment);
> +

This is not going to work out with tsc-scaling. The tsc-offset is
applied _after_ the hardware-tsc. Just scaling the offset with the same
factor will not give you the hardware tsc-value you expect.

	Joerg