linux-kernel - [PATCH v3 4/4] KVM: arm64: Clear active

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Message-ID: <20210729104009.382-5-shameerali.kolothum.thodi@huawei.com>
Date:   Thu, 29 Jul 2021 11:40:09 +0100
From:   Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
To:     <linux-arm-kernel@...ts.infradead.org>,
        <kvmarm@...ts.cs.columbia.edu>, <linux-kernel@...r.kernel.org>
CC:     <maz@...nel.org>, <will@...nel.org>, <catalin.marinas@....com>,
        <james.morse@....com>, <julien.thierry.kdev@...il.com>,
        <suzuki.poulose@....com>, <jean-philippe@...aro.org>,
        <Alexandru.Elisei@....com>, <qperret@...gle.com>,
        <linuxarm@...wei.com>
Subject: [PATCH v3 4/4] KVM: arm64: Clear active_vmids 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, clear active_vmids when scheduling out a vCPU.

Suggested-by: Will Deacon <will@...nel.org>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
---
 arch/arm64/include/asm/kvm_host.h | 1 +
 arch/arm64/kvm/arm.c              | 1 +
 arch/arm64/kvm/vmid.c             | 6 ++++++
 3 files changed, 8 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index bb993bce1363..d93141cb8d16 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -687,6 +687,7 @@ 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 077e55a511a9..b134a1b89c84 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -435,6 +435,7 @@ 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 5584e84aed95..5fd51f5445c1 100644
--- a/arch/arm64/kvm/vmid.c
+++ b/arch/arm64/kvm/vmid.c
@@ -116,6 +116,12 @@ static u64 new_vmid(struct kvm_vmid *kvm_vmid)
 	return idx2vmid(vmid) | generation;
 }
 
+/* Call with preemption disabled */
+void kvm_arm_vmid_clear_active(void)
+{
+	atomic64_set(this_cpu_ptr(&active_vmids), 0);
+}
+
 void kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
 {
 	unsigned long flags;
-- 
2.17.1