KVM: x86: Move TSC offset writes to common code

Also, ensure that the storing of the offset and the reading of the TSC
are never preempted by taking a spinlock.  While the lock is overkill
now, it is useful later in this patch series.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6056a23dc4cf1f16639d5162c07e7038844db887..a215153f1ff637b1fe9e7af222d7bcceba7a26f1 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -395,6 +395,7 @@ struct kvm_arch {
 
        unsigned long irq_sources_bitmap;
        s64 kvmclock_offset;
+       spinlock_t tsc_write_lock;
 
        struct kvm_xen_hvm_config xen_hvm_config;
 
@@ -521,6 +522,8 @@ struct kvm_x86_ops {
 
        bool (*has_wbinvd_exit)(void);
 
+       void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
+
        const struct trace_print_flags *exit_reasons_str;
 };
 

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index e06f00d1f15c53262d1d1b1c831576561a998c04..ea41c551fa447b7ccc58b11bd5e1f7d7417b74f5 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -915,7 +915,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
        svm->vmcb_pa = page_to_pfn(page) << PAGE_SHIFT;
        svm->asid_generation = 0;
        init_vmcb(svm);
-       svm_write_tsc_offset(&svm->vcpu, 0-native_read_tsc());
+       kvm_write_tsc(&svm->vcpu, 0);
 
        err = fx_init(&svm->vcpu);
        if (err)
@@ -2581,7 +2581,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
 
        switch (ecx) {
        case MSR_IA32_TSC:
-               svm_write_tsc_offset(vcpu, data - native_read_tsc());
+               kvm_write_tsc(vcpu, data);
                break;
        case MSR_STAR:
                svm->vmcb->save.star = data;
@@ -3551,6 +3551,8 @@ static struct kvm_x86_ops svm_x86_ops = {
        .set_supported_cpuid = svm_set_supported_cpuid,
 
        .has_wbinvd_exit = svm_has_wbinvd_exit,
+
+       .write_tsc_offset = svm_write_tsc_offset,
 };
 
 static int __init svm_init(void)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index d9bec5ee38b871e4cebde3a7737f03933b7129e6..138746d3afe98395c627bd671ef00ebdf78a3dda 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1146,10 +1146,9 @@ 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
+ * writes 'offset' into guest's timestamp counter offset register
  */
-static void vmx_write_tsc_offset(u64 offset)
+static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
 {
        vmcs_write64(TSC_OFFSET, offset);
 }
@@ -1224,7 +1223,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
 {
        struct vcpu_vmx *vmx = to_vmx(vcpu);
        struct shared_msr_entry *msr;
-       u64 host_tsc;
        int ret = 0;
 
        switch (msr_index) {
@@ -1254,8 +1252,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
                vmcs_writel(GUEST_SYSENTER_ESP, data);
                break;
        case MSR_IA32_TSC:
-               rdtscll(host_tsc);
-               vmx_write_tsc_offset(data - host_tsc);
+               kvm_write_tsc(vcpu, data);
                break;
        case MSR_IA32_CR_PAT:
                if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
@@ -2653,7 +2650,7 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
                vmx->vcpu.arch.cr4_guest_owned_bits |= X86_CR4_PGE;
        vmcs_writel(CR4_GUEST_HOST_MASK, ~vmx->vcpu.arch.cr4_guest_owned_bits);
 
-       vmx_write_tsc_offset(0-native_read_tsc());
+       kvm_write_tsc(&vmx->vcpu, 0);
 
        return 0;
 }
@@ -4348,6 +4345,8 @@ static struct kvm_x86_ops vmx_x86_ops = {
        .set_supported_cpuid = vmx_set_supported_cpuid,
 
        .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
+
+       .write_tsc_offset = vmx_write_tsc_offset,
 };
 
 static int __init vmx_init(void)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 8b0c51a1adaa690912935956c84a8db076a83b0f..886132b6ef14064e901f02a0f74d533aed24c684 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -895,6 +895,22 @@ static void kvm_set_time_scale(uint32_t tsc_khz, struct pvclock_vcpu_time_info *
 
 static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz);
 
+void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data)
+{
+       struct kvm *kvm = vcpu->kvm;
+       u64 offset;
+       unsigned long flags;
+
+       spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags);
+       offset = data - native_read_tsc();
+       kvm_x86_ops->write_tsc_offset(vcpu, offset);
+       spin_unlock_irqrestore(&kvm->arch.tsc_write_lock, flags);
+
+       /* Reset of TSC must disable overshoot protection below */
+       vcpu->arch.hv_clock.tsc_timestamp = 0;
+}
+EXPORT_SYMBOL_GPL(kvm_write_tsc);
+
 static void kvm_write_guest_time(struct kvm_vcpu *v)
 {
        struct timespec ts;
@@ -5495,6 +5511,8 @@ 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);
 
+       spin_lock_init(&kvm->arch.tsc_write_lock);
+
        return kvm;
 }
 

diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index b7a404722d2b791efa2a9ae12d636ec2e5fd0a83..2d6385e44ccfe5608cae1f8e418ec6e06b01f867 100644 (file)
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -68,4 +68,6 @@ static inline int is_paging(struct kvm_vcpu *vcpu)
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
 
+void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);
+
 #endif