arm64: KVM: Fix system register enumeration

commit 5d8d4af24460d079ecdb190254b14b528add1228 upstream.

The introduction of the SVE registers to userspace started with a
refactoring of the way we expose any register via the ONE_REG
interface.

Unfortunately, this change doesn't exactly behave as expected
if the number of registers is non-zero and consider everything
to be an error. The visible result is that QEMU barfs very early
when creating vcpus.

Make sure we only exit early in case there is an actual error, rather
than a positive number of registers...

Fixes: be25bbb392fa ("KVM: arm64: Factor out core register ID enumeration")
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Takahiro Itazuri <itazur@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 563a9f31b83d35f4f9c5f98329e48db6c90cd158..b509afa0547014dd0b41131551a452119105ddb1 100644 (file)
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -333,17 +333,17 @@ int kvm_arm_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
        int ret;
 
        ret = kvm_arm_copy_core_reg_indices(uindices);
-       if (ret)
+       if (ret < 0)
                return ret;
        uindices += ret;
 
        ret = kvm_arm_copy_fw_reg_indices(vcpu, uindices);
-       if (ret)
+       if (ret < 0)
                return ret;
        uindices += kvm_arm_get_fw_num_regs(vcpu);
 
        ret = copy_timer_indices(vcpu, uindices);
-       if (ret)
+       if (ret < 0)
                return ret;
        uindices += NUM_TIMER_REGS;