linux-kernel - [PATCH] KVM: arm64: vgic-v3: Clear pending bit in guest memory after synchronization

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Date:   Tue, 31 Mar 2020 11:12:45 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     <kvmarm@...ts.cs.columbia.edu>
CC:     <maz@...nel.org>, <eric.auger@...hat.com>,
        <andre.przywara@....com>, <james.morse@....com>,
        <julien.thierry.kdev@...il.com>, <suzuki.poulose@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <wanghaibin.wang@...wei.com>,
        Zenghui Yu <yuzenghui@...wei.com>
Subject: [PATCH] KVM: arm64: vgic-v3: Clear pending bit in guest memory after synchronization

When LPI support is enabled at redistributor level, VGIC will potentially
load the correspond LPI penging table and sync it into the pending_latch.
To avoid keeping the 'consumed' pending bits lying around in guest memory
(though they're not used), let's clear them after synchronization.

The similar work had been done in vgic_v3_lpi_sync_pending_status().

Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
---
 virt/kvm/arm/vgic/vgic-its.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index d53d34a33e35..905760bfa404 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -435,6 +435,7 @@ static int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu)
 
 	for (i = 0; i < nr_irqs; i++) {
 		int byte_offset, bit_nr;
+		bool status;
 
 		byte_offset = intids[i] / BITS_PER_BYTE;
 		bit_nr = intids[i] % BITS_PER_BYTE;
@@ -447,22 +448,32 @@ static int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu)
 			ret = kvm_read_guest_lock(vcpu->kvm,
 						  pendbase + byte_offset,
 						  &pendmask, 1);
-			if (ret) {
-				kfree(intids);
-				return ret;
-			}
+			if (ret)
+				goto out;
 			last_byte_offset = byte_offset;
 		}
 
+		status = pendmask & (1 << bit_nr);
+
 		irq = vgic_get_irq(vcpu->kvm, NULL, intids[i]);
 		raw_spin_lock_irqsave(&irq->irq_lock, flags);
-		irq->pending_latch = pendmask & (1U << bit_nr);
+		irq->pending_latch = status;
 		vgic_queue_irq_unlock(vcpu->kvm, irq, flags);
 		vgic_put_irq(vcpu->kvm, irq);
+
+		if (status) {
+			/* clear consumed data */
+			pendmask &= ~(1 << bit_nr);
+			ret = kvm_write_guest_lock(vcpu->kvm,
+						   pendbase + byte_offset,
+						   &pendmask, 1);
+			if (ret)
+				goto out;
+		}
 	}
 
+out:
 	kfree(intids);
-
 	return ret;
 }
 
-- 
2.19.1