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authorLinus Torvalds <torvalds@linux-foundation.org>2015-04-13 09:47:01 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-13 09:47:01 -0700
commit900360131066f192c82311a098d03d6ac6429e20 (patch)
treee9681537a2d1f75fa5be21d8f1116f9f0ba8a391 /arch/x86/vdso
parent4541fec3104bef0c60633f9e180be94ea5ccc2b7 (diff)
parentca3f0874723fad81d0c701b63ae3a17a408d5f25 (diff)
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 ...
Diffstat (limited to 'arch/x86/vdso')
-rw-r--r--arch/x86/vdso/vclock_gettime.c34
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;