Like ASID allocator, we copy the active_vmids into the
reserved_vmids on a rollover. But it's unlikely that
every CPU will have a vCPU as current task and we may
end up unnecessarily reserving the VMID space.
Hence, set active_vmids to an invalid one when scheduling
out a vCPU.
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
---
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/kvm/arm.c | 1 +
arch/arm64/kvm/vmid.c | 25 ++++++++++++++++++++++---
3 files changed, 24 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 752d4408e3d0..22f952effd03 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -692,6 +692,7 @@ extern unsigned int kvm_arm_vmid_bits;
int kvm_arm_vmid_alloc_init(void);
void kvm_arm_vmid_alloc_free(void);
void kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid);
+void kvm_arm_vmid_clear_active(void);
static inline void kvm_arm_pvtime_vcpu_init(struct kvm_vcpu_arch *vcpu_arch)
{
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 0544011b0fc6..bfe926805240 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -431,6 +431,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
kvm_timer_vcpu_put(vcpu);
kvm_vgic_put(vcpu);
kvm_vcpu_pmu_restore_host(vcpu);
+ kvm_arm_vmid_clear_active();
vcpu->cpu = -1;
}
diff --git a/arch/arm64/kvm/vmid.c b/arch/arm64/kvm/vmid.c
index 9aff692b6b7d..966ebb2d12e5 100644
--- a/arch/arm64/kvm/vmid.c
+++ b/arch/arm64/kvm/vmid.c
@@ -32,6 +32,13 @@ static DEFINE_PER_CPU(u64, reserved_vmids);
#define vmid2idx(vmid) ((vmid) & ~VMID_MASK)
#define idx2vmid(idx) vmid2idx(idx)
+/*
+ * As vmid #0 is always reserved, we will never allocate one
+ * as below and can be treated as invalid. This is used to
+ * set the active_vmids on vCPU schedule out.
+ */
+#define VMID_ACTIVE_INVALID VMID_FIRST_VERSION
+
#define vmid_gen_match(vmid) \
(!(((vmid) ^ atomic64_read(&vmid_generation)) >> kvm_arm_vmid_bits))
@@ -122,6 +129,12 @@ static u64 new_vmid(struct kvm_vmid *kvm_vmid)
return vmid;
}
+/* Called from vCPU sched out with preemption disabled */
+void kvm_arm_vmid_clear_active(void)
+{
+ atomic64_set(this_cpu_ptr(&active_vmids), VMID_ACTIVE_INVALID);
+}
+
void kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
{
unsigned long flags;
@@ -132,11 +145,17 @@ void kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
/*
* Please refer comments in check_and_switch_context() in
* arch/arm64/mm/context.c.
+ *
+ * Unlike ASID allocator, we set the active_vmids to
+ * VMID_ACTIVE_INVALID on vCPU schedule out to avoid
+ * reserving the VMID space needlessly on rollover.
+ * Hence explicitly check here for a "!= 0" to
+ * handle the sync with a concurrent rollover.
*/
old_active_vmid = atomic64_read(this_cpu_ptr(&active_vmids));
- if (old_active_vmid && vmid_gen_match(vmid) &&
- atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_vmids),
- old_active_vmid, vmid))
+ if (old_active_vmid != 0 && vmid_gen_match(vmid) &&
+ 0 != atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_vmids),
+ old_active_vmid, vmid))
return;
raw_spin_lock_irqsave(&cpu_vmid_lock, flags);
--
2.17.1
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