linux-kernel - [PATCH v6 7/9] KVM: arm/arm64: vgic-its: Free caches when GITS

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Date:   Thu, 26 Oct 2017 17:23:09 +0200
From:   Eric Auger <eric.auger@...hat.com>
To:     eric.auger.pro@...il.com, eric.auger@...hat.com,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        kvmarm@...ts.cs.columbia.edu, marc.zyngier@....com,
        cdall@...aro.org, peter.maydell@...aro.org, andre.przywara@....com,
        wanghaibin.wang@...wei.com
Cc:     wu.wubin@...wei.com, drjones@...hat.com, wei@...hat.com
Subject: [PATCH v6 7/9] KVM: arm/arm64: vgic-its: Free caches when GITS_BASER Valid bit is cleared

When the GITS_BASER<n>.Valid gets cleared, the data structures in
guest RAM are not valid anymore. The device, collection
and LPI lists stored in the in-kernel ITS represent the same
information in some form of cache. So let's void the cache.

Signed-off-by: Eric Auger <eric.auger@...hat.com>

---
v5 -> v6:
- rename type into device_type and revert tthe u64 -> int change
- remove the default clause
- take the its mutex lock around vgic_its_free_device/collection_list

v4 -> v5:
- add comment about locking

v2 -> v3:
- add a comment and clear cache in if block
---
 virt/kvm/arm/vgic/vgic-its.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index 5b7be85..2a92d4d 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -1428,7 +1428,7 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
 				      unsigned long val)
 {
 	const struct vgic_its_abi *abi = vgic_its_get_abi(its);
-	u64 entry_size, device_type;
+	u64 entry_size, table_type;
 	u64 reg, *regptr, clearbits = 0;
 
 	/* When GITS_CTLR.Enable is 1, we ignore write accesses. */
@@ -1439,12 +1439,12 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
 	case 0:
 		regptr = &its->baser_device_table;
 		entry_size = abi->dte_esz;
-		device_type = GITS_BASER_TYPE_DEVICE;
+		table_type = GITS_BASER_TYPE_DEVICE;
 		break;
 	case 1:
 		regptr = &its->baser_coll_table;
 		entry_size = abi->cte_esz;
-		device_type = GITS_BASER_TYPE_COLLECTION;
+		table_type = GITS_BASER_TYPE_COLLECTION;
 		clearbits = GITS_BASER_INDIRECT;
 		break;
 	default:
@@ -1456,10 +1456,28 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
 	reg &= ~clearbits;
 
 	reg |= (entry_size - 1) << GITS_BASER_ENTRY_SIZE_SHIFT;
-	reg |= device_type << GITS_BASER_TYPE_SHIFT;
+	reg |= table_type << GITS_BASER_TYPE_SHIFT;
 	reg = vgic_sanitise_its_baser(reg);
 
 	*regptr = reg;
+
+	/*
+	 * If the table is no longer valid, we clear the associated cached data.
+	 * Note: there cannot be any race with save/restore code which locks
+	 * all vcpus.
+	 */
+	if (!(reg & GITS_BASER_VALID)) {
+		mutex_lock(&its->its_lock);
+		switch (table_type) {
+		case GITS_BASER_TYPE_DEVICE:
+			vgic_its_free_device_list(kvm, its);
+			break;
+		case GITS_BASER_TYPE_COLLECTION:
+			vgic_its_free_collection_list(kvm, its);
+			break;
+		}
+		mutex_unlock(&its->its_lock);
+	}
 }
 
 static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,
-- 
2.5.5