arm/arm64: KVM: Clarify KVM_ARM_VCPU_INIT ABI

It is not clear that this ioctl can be called multiple times for a given
vcpu.  Userspace already does this, so clarify the ABI.

Also specify that userspace is expected to always make secondary and
subsequent calls to the ioctl with the same parameters for the VCPU as
the initial call (which userspace also already does).

Add code to check that userspace doesn't violate that ABI in the future,
and move the kvm_vcpu_set_target() function which is currently
duplicated between the 32-bit and 64-bit versions in guest.c to a common
static function in arm.c, shared between both architectures.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index bb82a906e51e73fe6fcfa7cb0c066475930c06a6..81f1b974c06a5c8d18e2f3a22ed91862ffff154b 100644 (file)
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -2453,6 +2453,11 @@ return ENOEXEC for that vcpu.
 Note that because some registers reflect machine topology, all vcpus
 should be created before this ioctl is invoked.
 
+Userspace can call this function multiple times for a given vcpu, including
+after the vcpu has been run. This will reset the vcpu to its initial
+state. All calls to this function after the initial call must use the same
+target and same set of feature flags, otherwise EINVAL will be returned.
+
 Possible features:
        - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state.
          Depends on KVM_CAP_ARM_PSCI.  If not set, the CPU will be powered on

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 53036e21756b6b1efaef6e9c34e64ae3117f30d2..254e0650e48bbc1d07a81d091c8e33570f983851 100644 (file)
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -150,8 +150,6 @@ struct kvm_vcpu_stat {
        u32 halt_wakeup;
 };
 
-int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
-                       const struct kvm_vcpu_init *init);
 int kvm_vcpu_preferred_target(struct kvm_vcpu_init *init);
 unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
 int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 24c9ca4076b242ffe01447e8e153307b793da96a..4043769583e7fc4e4a68311ff7703b984b1e4d83 100644 (file)
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -263,6 +263,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 {
        /* Force users to call KVM_ARM_VCPU_INIT */
        vcpu->arch.target = -1;
+       bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES);
 
        /* Set up the timer */
        kvm_timer_vcpu_init(vcpu);
@@ -649,6 +650,48 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level,
        return -EINVAL;
 }
 
+static int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
+                              const struct kvm_vcpu_init *init)
+{
+       unsigned int i;
+       int phys_target = kvm_target_cpu();
+
+       if (init->target != phys_target)
+               return -EINVAL;
+
+       /*
+        * Secondary and subsequent calls to KVM_ARM_VCPU_INIT must
+        * use the same target.
+        */
+       if (vcpu->arch.target != -1 && vcpu->arch.target != init->target)
+               return -EINVAL;
+
+       /* -ENOENT for unknown features, -EINVAL for invalid combinations. */
+       for (i = 0; i < sizeof(init->features) * 8; i++) {
+               bool set = (init->features[i / 32] & (1 << (i % 32)));
+
+               if (set && i >= KVM_VCPU_MAX_FEATURES)
+                       return -ENOENT;
+
+               /*
+                * Secondary and subsequent calls to KVM_ARM_VCPU_INIT must
+                * use the same feature set.
+                */
+               if (vcpu->arch.target != -1 && i < KVM_VCPU_MAX_FEATURES &&
+                   test_bit(i, vcpu->arch.features) != set)
+                       return -EINVAL;
+
+               if (set)
+                       set_bit(i, vcpu->arch.features);
+       }
+
+       vcpu->arch.target = phys_target;
+
+       /* Now we know what it is, we can reset it. */
+       return kvm_reset_vcpu(vcpu);
+}
+
+
 static int kvm_arch_vcpu_ioctl_vcpu_init(struct kvm_vcpu *vcpu,
                                         struct kvm_vcpu_init *init)
 {

diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c
index 8c97208b9b970c4d799e76ee7096d58dfb8c33ae..384bab67c4629a9bece251d5577c9bf908f8348f 100644 (file)
--- a/arch/arm/kvm/guest.c
+++ b/arch/arm/kvm/guest.c
@@ -273,31 +273,6 @@ int __attribute_const__ kvm_target_cpu(void)
        }
 }
 
-int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
-                       const struct kvm_vcpu_init *init)
-{
-       unsigned int i;
-
-       /* We can only cope with guest==host and only on A15/A7 (for now). */
-       if (init->target != kvm_target_cpu())
-               return -EINVAL;
-
-       vcpu->arch.target = init->target;
-       bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES);
-
-       /* -ENOENT for unknown features, -EINVAL for invalid combinations. */
-       for (i = 0; i < sizeof(init->features) * 8; i++) {
-               if (test_bit(i, (void *)init->features)) {
-                       if (i >= KVM_VCPU_MAX_FEATURES)
-                               return -ENOENT;
-                       set_bit(i, vcpu->arch.features);
-               }
-       }
-
-       /* Now we know what it is, we can reset it. */
-       return kvm_reset_vcpu(vcpu);
-}
-
 int kvm_vcpu_preferred_target(struct kvm_vcpu_init *init)
 {
        int target = kvm_target_cpu();

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2012c4ba8d67bf15c484048b4a0fe5b68f8e1b94..65c615294589f242a2d62694695002882d5cc1a8 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -165,8 +165,6 @@ struct kvm_vcpu_stat {
        u32 halt_wakeup;
 };
 
-int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
-                       const struct kvm_vcpu_init *init);
 int kvm_vcpu_preferred_target(struct kvm_vcpu_init *init);
 unsigned long kvm_arm_num_regs(struct kvm_vcpu *vcpu);
 int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices);

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 84d5959ff8742b64d37af40046a1c4fc8bd6e641..9535bd555d1d47cf190f78306eb879484d70a261 100644 (file)
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -296,31 +296,6 @@ int __attribute_const__ kvm_target_cpu(void)
        return -EINVAL;
 }
 
-int kvm_vcpu_set_target(struct kvm_vcpu *vcpu,
-                       const struct kvm_vcpu_init *init)
-{
-       unsigned int i;
-       int phys_target = kvm_target_cpu();
-
-       if (init->target != phys_target)
-               return -EINVAL;
-
-       vcpu->arch.target = phys_target;
-       bitmap_zero(vcpu->arch.features, KVM_VCPU_MAX_FEATURES);
-
-       /* -ENOENT for unknown features, -EINVAL for invalid combinations. */
-       for (i = 0; i < sizeof(init->features) * 8; i++) {
-               if (init->features[i / 32] & (1 << (i % 32))) {
-                       if (i >= KVM_VCPU_MAX_FEATURES)
-                               return -ENOENT;
-                       set_bit(i, vcpu->arch.features);
-               }
-       }
-
-       /* Now we know what it is, we can reset it. */
-       return kvm_reset_vcpu(vcpu);
-}
-
 int kvm_vcpu_preferred_target(struct kvm_vcpu_init *init)
 {
        int target = kvm_target_cpu();