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author | Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> | 2021-11-22 12:18:44 +0000 |
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committer | Marc Zyngier <maz@kernel.org> | 2022-02-08 14:57:04 +0000 |
commit | 100b4f092f878dc379f1fcef9ce567c25dee3473 (patch) | |
tree | 94812b659483a3d9daf59f9bc0d0e70d3784ccab /arch/arm64/kvm/vmid.c | |
parent | 3248136b3637e1671e4fa46e32e2122f9ec4bc3d (diff) | |
download | linux-stable-100b4f092f878dc379f1fcef9ce567c25dee3473.tar.gz linux-stable-100b4f092f878dc379f1fcef9ce567c25dee3473.tar.bz2 linux-stable-100b4f092f878dc379f1fcef9ce567c25dee3473.zip |
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: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211122121844.867-5-shameerali.kolothum.thodi@huawei.com
Diffstat (limited to 'arch/arm64/kvm/vmid.c')
-rw-r--r-- | arch/arm64/kvm/vmid.c | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/arch/arm64/kvm/vmid.c b/arch/arm64/kvm/vmid.c index 9aff692b6b7d..8d5f0506fd87 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 @@ set_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); |