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authorAndre Przywara <andre.przywara@arm.com>2015-12-01 22:36:37 +0000
committerChristoffer Dall <christoffer.dall@linaro.org>2016-05-20 15:40:03 +0200
commit7d450e2821710718fd6703e9c486249cee913bab (patch)
tree02dc0e9f84440e3d77ee72f32e27d53bcedda758 /virt
parentc3199f28e09496aa9fec9313b4f6e90e7dc913f0 (diff)
downloadlinux-7d450e2821710718fd6703e9c486249cee913bab.tar.gz
linux-7d450e2821710718fd6703e9c486249cee913bab.tar.xz
KVM: arm/arm64: vgic-new: Add userland access to VGIC dist registers
Userland may want to save and restore the state of the in-kernel VGIC, so we provide the code which takes a userland request and translate that into calls to our MMIO framework. From Christoffer: When accessing the VGIC state from userspace we really don't want a VCPU to be messing with the state at the same time, and the API specifies that we should return -EBUSY if any VCPUs are running. Check and prevent VCPUs from running by grabbing their mutexes, one by one, and error out if we fail. (Note: This could potentially be simplified to just do a simple check and see if any VCPUs are running, and return -EBUSY then, without enforcing the locking throughout the duration of the uaccess, if we think that taking/releasing all these mutexes for every single GIC register access is too heavyweight.) Signed-off-by: Andre Przywara <andre.przywara@arm.com> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Diffstat (limited to 'virt')
-rw-r--r--virt/kvm/arm/vgic/vgic-kvm-device.c55
1 files changed, 54 insertions, 1 deletions
diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
index 7862128..9ee27cb 100644
--- a/virt/kvm/arm/vgic/vgic-kvm-device.c
+++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
@@ -238,7 +238,60 @@ static int vgic_attr_regs_access(struct kvm_device *dev,
struct kvm_device_attr *attr,
u32 *reg, bool is_write)
{
- return -ENXIO;
+ gpa_t addr;
+ int cpuid, ret, c;
+ struct kvm_vcpu *vcpu, *tmp_vcpu;
+ int vcpu_lock_idx = -1;
+
+ cpuid = (attr->attr & KVM_DEV_ARM_VGIC_CPUID_MASK) >>
+ KVM_DEV_ARM_VGIC_CPUID_SHIFT;
+ vcpu = kvm_get_vcpu(dev->kvm, cpuid);
+ addr = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK;
+
+ mutex_lock(&dev->kvm->lock);
+
+ ret = vgic_init(dev->kvm);
+ if (ret)
+ goto out;
+
+ if (cpuid >= atomic_read(&dev->kvm->online_vcpus)) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /*
+ * Any time a vcpu is run, vcpu_load is called which tries to grab the
+ * vcpu->mutex. By grabbing the vcpu->mutex of all VCPUs we ensure
+ * that no other VCPUs are run and fiddle with the vgic state while we
+ * access it.
+ */
+ ret = -EBUSY;
+ kvm_for_each_vcpu(c, tmp_vcpu, dev->kvm) {
+ if (!mutex_trylock(&tmp_vcpu->mutex))
+ goto out;
+ vcpu_lock_idx = c;
+ }
+
+ switch (attr->group) {
+ case KVM_DEV_ARM_VGIC_GRP_CPU_REGS:
+ ret = -EINVAL;
+ break;
+ case KVM_DEV_ARM_VGIC_GRP_DIST_REGS:
+ ret = vgic_v2_dist_uaccess(vcpu, is_write, addr, reg);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+out:
+ for (; vcpu_lock_idx >= 0; vcpu_lock_idx--) {
+ tmp_vcpu = kvm_get_vcpu(dev->kvm, vcpu_lock_idx);
+ mutex_unlock(&tmp_vcpu->mutex);
+ }
+
+ mutex_unlock(&dev->kvm->lock);
+ return ret;
}
/* V2 ops */