KVM: x86: Fix potential preemption when get the current kvmclock timestamp

[karo-tx-linux.git] / arch / x86 / kvm / x86.c

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 464da936c53dd96b2f9e89f1f0ef715bac3eafe2..3b5fc7e35f6ef5e99cdf0e82d8c1f342cfad28ae 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1763,6 +1763,7 @@ u64 get_kvmclock_ns(struct kvm *kvm)
 {
        struct kvm_arch *ka = &kvm->arch;
        struct pvclock_vcpu_time_info hv_clock;
+       u64 ret;
 
        spin_lock(&ka->pvclock_gtod_sync_lock);
        if (!ka->use_master_clock) {
@@ -1774,10 +1775,17 @@ u64 get_kvmclock_ns(struct kvm *kvm)
        hv_clock.system_time = ka->master_kernel_ns + ka->kvmclock_offset;
        spin_unlock(&ka->pvclock_gtod_sync_lock);
 
+       /* both __this_cpu_read() and rdtsc() should be on the same cpu */
+       get_cpu();
+
        kvm_get_time_scale(NSEC_PER_SEC, __this_cpu_read(cpu_tsc_khz) * 1000LL,
                           &hv_clock.tsc_shift,
                           &hv_clock.tsc_to_system_mul);
-       return __pvclock_read_cycles(&hv_clock, rdtsc());
+       ret = __pvclock_read_cycles(&hv_clock, rdtsc());
+
+       put_cpu();
+
+       return ret;
 }
 
 static void kvm_setup_pvclock_page(struct kvm_vcpu *v)
@@ -3288,11 +3296,14 @@ static void kvm_vcpu_ioctl_x86_get_xsave(struct kvm_vcpu *vcpu,
        }
 }
 
+#define XSAVE_MXCSR_OFFSET 24
+
 static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
                                        struct kvm_xsave *guest_xsave)
 {
        u64 xstate_bv =
                *(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)];
+       u32 mxcsr = *(u32 *)&guest_xsave->region[XSAVE_MXCSR_OFFSET / sizeof(u32)];
 
        if (boot_cpu_has(X86_FEATURE_XSAVE)) {
                /*
@@ -3300,11 +3311,13 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
                 * CPUID leaf 0xD, index 0, EDX:EAX.  This is for compatibility
                 * with old userspace.
                 */
-               if (xstate_bv & ~kvm_supported_xcr0())
+               if (xstate_bv & ~kvm_supported_xcr0() ||
+                       mxcsr & ~mxcsr_feature_mask)
                        return -EINVAL;
                load_xsave(vcpu, (u8 *)guest_xsave->region);
        } else {
-               if (xstate_bv & ~XFEATURE_MASK_FPSSE)
+               if (xstate_bv & ~XFEATURE_MASK_FPSSE ||
+                       mxcsr & ~mxcsr_feature_mask)
                        return -EINVAL;
                memcpy(&vcpu->arch.guest_fpu.state.fxsave,
                        guest_xsave->region, sizeof(struct fxregs_state));