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Commit ea26e4ec authored by Paolo Bonzini's avatar Paolo Bonzini
Browse files

KVM: x86: drop TSC offsetting kvm_x86_ops to fix KVM_GET/SET_CLOCK 



Since commit a545ab6a ("kvm: x86: add tsc_offset field to struct
kvm_vcpu_arch", 2016-09-07) the offset between host and L1 TSC is
cached and need not be fished out of the VMCS or VMCB.  This means
that we can implement adjust_tsc_offset_guest and read_l1_tsc
entirely in generic code.  The simplification is particularly
significant for VMX code, where vmx->nested.vmcs01_tsc_offset
was duplicating what is now in vcpu->arch.tsc_offset.  Therefore
the vmcs01_tsc_offset can be dropped completely.

More importantly, this fixes KVM_GET_CLOCK/KVM_SET_CLOCK
which, after commit 108b249c ("KVM: x86: introduce get_kvmclock_ns",
2016-09-01) called read_l1_tsc while the VMCS was not loaded.
It thus returned bogus values on Intel CPUs.

Fixes: 108b249c
Reported-by: default avatarRoman Kagan <rkagan@virtuozzo.com>
Reviewed-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent bd768e14

arch/x86/include/asm/kvm_host.h

+0 −3
Original line number Diff line number Diff line
@@ -948,7 +948,6 @@ struct kvm_x86_ops { 
	int (*get_lpage_level)(void);

	bool (*rdtscp_supported)(void);

	bool (*invpcid_supported)(void);

	void (*adjust_tsc_offset_guest)(struct kvm_vcpu *vcpu, s64 adjustment);



	void (*set_tdp_cr3)(struct kvm_vcpu *vcpu, unsigned long cr3);
@@ -958,8 +957,6 @@ struct kvm_x86_ops { 


	void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);



	u64 (*read_l1_tsc)(struct kvm_vcpu *vcpu, u64 host_tsc);



	void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2);



	int (*check_intercept)(struct kvm_vcpu *vcpu,

arch/x86/kvm/svm.c

+0 −23
Original line number Diff line number Diff line
@@ -1138,21 +1138,6 @@ static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) 
	mark_dirty(svm->vmcb, VMCB_INTERCEPTS);

}



static void svm_adjust_tsc_offset_guest(struct kvm_vcpu *vcpu, s64 adjustment)

{

	struct vcpu_svm *svm = to_svm(vcpu);



	svm->vmcb->control.tsc_offset += adjustment;

	if (is_guest_mode(vcpu))

		svm->nested.hsave->control.tsc_offset += adjustment;

	else

		trace_kvm_write_tsc_offset(vcpu->vcpu_id,

				     svm->vmcb->control.tsc_offset - adjustment,

				     svm->vmcb->control.tsc_offset);



	mark_dirty(svm->vmcb, VMCB_INTERCEPTS);

}



static void avic_init_vmcb(struct vcpu_svm *svm)

{

	struct vmcb *vmcb = svm->vmcb;
@@ -3449,12 +3434,6 @@ static int cr8_write_interception(struct vcpu_svm *svm) 
	return 0;

}



static u64 svm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)

{

	struct vmcb *vmcb = get_host_vmcb(to_svm(vcpu));

	return vmcb->control.tsc_offset + host_tsc;

}



static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)

{

	struct vcpu_svm *svm = to_svm(vcpu);
@@ -5422,8 +5401,6 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = { 
	.has_wbinvd_exit = svm_has_wbinvd_exit,



	.write_tsc_offset = svm_write_tsc_offset,

	.adjust_tsc_offset_guest = svm_adjust_tsc_offset_guest,

	.read_l1_tsc = svm_read_l1_tsc,



	.set_tdp_cr3 = set_tdp_cr3,

arch/x86/kvm/vmx.c

+3 −36
Original line number Diff line number Diff line
@@ -421,7 +421,6 @@ struct nested_vmx { 
	/* vmcs02_list cache of VMCSs recently used to run L2 guests */

	struct list_head vmcs02_pool;

	int vmcs02_num;

	u64 vmcs01_tsc_offset;

	bool change_vmcs01_virtual_x2apic_mode;

	/* L2 must run next, and mustn't decide to exit to L1. */

	bool nested_run_pending;
@@ -2604,20 +2603,6 @@ static u64 guest_read_tsc(struct kvm_vcpu *vcpu) 
	return kvm_scale_tsc(vcpu, host_tsc) + tsc_offset;

}



/*

 * Like guest_read_tsc, but always returns L1's notion of the timestamp

 * counter, even if a nested guest (L2) is currently running.

 */

static u64 vmx_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)

{

	u64 tsc_offset;



	tsc_offset = is_guest_mode(vcpu) ?

		to_vmx(vcpu)->nested.vmcs01_tsc_offset :

		vmcs_read64(TSC_OFFSET);

	return host_tsc + tsc_offset;

}



/*

 * writes 'offset' into guest's timestamp counter offset register

 */
@@ -2631,7 +2616,6 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) 
		 * to the newly set TSC to get L2's TSC.

		 */

		struct vmcs12 *vmcs12;

		to_vmx(vcpu)->nested.vmcs01_tsc_offset = offset;

		/* recalculate vmcs02.TSC_OFFSET: */

		vmcs12 = get_vmcs12(vcpu);

		vmcs_write64(TSC_OFFSET, offset +
@@ -2644,19 +2628,6 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset) 
	}

}



static void vmx_adjust_tsc_offset_guest(struct kvm_vcpu *vcpu, s64 adjustment)

{

	u64 offset = vmcs_read64(TSC_OFFSET);



	vmcs_write64(TSC_OFFSET, offset + adjustment);

	if (is_guest_mode(vcpu)) {

		/* Even when running L2, the adjustment needs to apply to L1 */

		to_vmx(vcpu)->nested.vmcs01_tsc_offset += adjustment;

	} else

		trace_kvm_write_tsc_offset(vcpu->vcpu_id, offset,

					   offset + adjustment);

}



static bool guest_cpuid_has_vmx(struct kvm_vcpu *vcpu)

{

	struct kvm_cpuid_entry2 *best = kvm_find_cpuid_entry(vcpu, 1, 0);
@@ -10061,9 +10032,9 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12) 


	if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETING)

		vmcs_write64(TSC_OFFSET,

			vmx->nested.vmcs01_tsc_offset + vmcs12->tsc_offset);

			vcpu->arch.tsc_offset + vmcs12->tsc_offset);

	else

		vmcs_write64(TSC_OFFSET, vmx->nested.vmcs01_tsc_offset);

		vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);

	if (kvm_has_tsc_control)

		decache_tsc_multiplier(vmx);
@@ -10293,8 +10264,6 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch) 


	enter_guest_mode(vcpu);



	vmx->nested.vmcs01_tsc_offset = vmcs_read64(TSC_OFFSET);



	if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))

		vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
@@ -10818,7 +10787,7 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason, 
	load_vmcs12_host_state(vcpu, vmcs12);



	/* Update any VMCS fields that might have changed while L2 ran */

	vmcs_write64(TSC_OFFSET, vmx->nested.vmcs01_tsc_offset);

	vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);

	if (vmx->hv_deadline_tsc == -1)

		vmcs_clear_bits(PIN_BASED_VM_EXEC_CONTROL,

				PIN_BASED_VMX_PREEMPTION_TIMER);
@@ -11339,8 +11308,6 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = { 
	.has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,



	.write_tsc_offset = vmx_write_tsc_offset,

	.adjust_tsc_offset_guest = vmx_adjust_tsc_offset_guest,

	.read_l1_tsc = vmx_read_l1_tsc,



	.set_tdp_cr3 = vmx_set_cr3,

arch/x86/kvm/x86.c

+3 −3
Original line number Diff line number Diff line
@@ -1409,7 +1409,7 @@ static u64 kvm_compute_tsc_offset(struct kvm_vcpu *vcpu, u64 target_tsc) 


u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)

{

	return kvm_x86_ops->read_l1_tsc(vcpu, kvm_scale_tsc(vcpu, host_tsc));

	return vcpu->arch.tsc_offset + kvm_scale_tsc(vcpu, host_tsc);

}

EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
@@ -1547,7 +1547,7 @@ EXPORT_SYMBOL_GPL(kvm_write_tsc); 
static inline void adjust_tsc_offset_guest(struct kvm_vcpu *vcpu,

					   s64 adjustment)

{

	kvm_x86_ops->adjust_tsc_offset_guest(vcpu, adjustment);

	kvm_vcpu_write_tsc_offset(vcpu, vcpu->arch.tsc_offset + adjustment);

}



static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
@@ -1555,7 +1555,7 @@ static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment) 
	if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio)

		WARN_ON(adjustment < 0);

	adjustment = kvm_scale_tsc(vcpu, (u64) adjustment);

	kvm_x86_ops->adjust_tsc_offset_guest(vcpu, adjustment);

	adjust_tsc_offset_guest(vcpu, adjustment);

}



#ifdef CONFIG_X86_64