Commit 100b4f09 authored by Shameer Kolothum's avatar Shameer Kolothum Committed by Marc Zyngier
Browse files

KVM: arm64: Make active_vmids invalid on vCPU schedule out 



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: default avatarShameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211122121844.867-5-shameerali.kolothum.thodi@huawei.com
parent 3248136b

arch/arm64/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -694,6 +694,7 @@ 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)

{

arch/arm64/kvm/arm.c

+1 −0
Original line number Diff line number Diff line
@@ -417,6 +417,7 @@ 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;

}

arch/arm64/kvm/vmid.c

+22 −3
Original line number Diff line number Diff line
@@ -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;
@@ -132,10 +145,16 @@ 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),

	if (old_active_vmid != 0 && vmid_gen_match(vmid) &&

	    0 != atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_vmids),

					  old_active_vmid, vmid))

		return;