Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull KVM updates from Paolo Bonzini:
 "First batch of KVM changes for 4.1

  The most interesting bit here is irqfd/ioeventfd support for ARM and
  ARM64.

  Summary:

  ARM/ARM64:
     fixes for live migration, irqfd and ioeventfd support (enabling
     vhost, too), page aging

  s390:
     interrupt handling rework, allowing to inject all local interrupts
     via new ioctl and to get/set the full local irq state for migration
     and introspection.  New ioctls to access memory by virtual address,
     and to get/set the guest storage keys.  SIMD support.

  MIPS:
     FPU and MIPS SIMD Architecture (MSA) support.  Includes some
     patches from Ralf Baechle's MIPS tree.

  x86:
     bugfixes (notably for pvclock, the others are small) and cleanups.
     Another small latency improvement for the TSC deadline timer"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (146 commits)
  KVM: use slowpath for cross page cached accesses
  kvm: mmu: lazy collapse small sptes into large sptes
  KVM: x86: Clear CR2 on VCPU reset
  KVM: x86: DR0-DR3 are not clear on reset
  KVM: x86: BSP in MSR_IA32_APICBASE is writable
  KVM: x86: simplify kvm_apic_map
  KVM: x86: avoid logical_map when it is invalid
  KVM: x86: fix mixed APIC mode broadcast
  KVM: x86: use MDA for interrupt matching
  kvm/ppc/mpic: drop unused IRQ_testbit
  KVM: nVMX: remove unnecessary double caching of MAXPHYADDR
  KVM: nVMX: checks for address bits beyond MAXPHYADDR on VM-entry
  KVM: x86: cache maxphyaddr CPUID leaf in struct kvm_vcpu
  KVM: vmx: pass error code with internal error #2
  x86: vdso: fix pvclock races with task migration
  KVM: remove kvm_read_hva and kvm_read_hva_atomic
  KVM: x86: optimize delivery of TSC deadline timer interrupt
  KVM: x86: extract blocking logic from __vcpu_run
  kvm: x86: fix x86 eflags fixed bit
  KVM: s390: migrate vcpu interrupt state
  ...

1 files changed, 19 insertions, 15 deletions

diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index 9793322751e0..40d2473836c9 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -82,18 +82,15 @@ static notrace cycle_t vread_pvclock(int *mode)
         cycle_t ret;
         u64 last;
         u32 version;
+        u32 migrate_count;
         u8 flags;
         unsigned cpu, cpu1;
 
 
         /*
-         * Note: hypervisor must guarantee that:
-         * 1. cpu ID number maps 1:1 to per-CPU pvclock time info.
-         * 2. that per-CPU pvclock time info is updated if the
-         *    underlying CPU changes.
-         * 3. that version is increased whenever underlying CPU
-         *    changes.
-         *
+         * When looping to get a consistent (time-info, tsc) pair, we
+         * also need to deal with the possibility we can switch vcpus,
+         * so make sure we always re-fetch time-info for the current vcpu.
          */
         do {
                 cpu = __getcpu() & VGETCPU_CPU_MASK;
@@ -102,20 +99,27 @@ static notrace cycle_t vread_pvclock(int *mode)
                  * __getcpu() calls (Gleb).
                  */
 
-                pvti = get_pvti(cpu);
+                /* Make sure migrate_count will change if we leave the VCPU. */
+                do {
+                        pvti = get_pvti(cpu);
+                        migrate_count = pvti->migrate_count;
+
+                        cpu1 = cpu;
+                        cpu = __getcpu() & VGETCPU_CPU_MASK;
+                } while (unlikely(cpu != cpu1));
 
                 version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags);
 
                 /*
                  * Test we're still on the cpu as well as the version.
-                 * We could have been migrated just after the first
-                 * vgetcpu but before fetching the version, so we
-                 * wouldn't notice a version change.
+                 * - We must read TSC of pvti's VCPU.
+                 * - KVM doesn't follow the versioning protocol, so data could
+                 *   change before version if we left the VCPU.
                  */
-                cpu1 = __getcpu() & VGETCPU_CPU_MASK;
-        } while (unlikely(cpu != cpu1 ||
-                          (pvti->pvti.version & 1) ||
-                          pvti->pvti.version != version));
+                smp_rmb();
+        } while (unlikely((pvti->pvti.version & 1) ||
+                          pvti->pvti.version != version ||
+                          pvti->migrate_count != migrate_count));
 
         if (unlikely(!(flags & PVCLOCK_TSC_STABLE_BIT)))
                 *mode = VCLOCK_NONE;