Re: [PATCH v2 29/30] KVM: PPC: add KVM_SET_ONE_REG/KVM_GET_ONE_REG to async ioctl

Hi Paul,
On Tue, May 15, 2018 at 04:15:26PM +1000, Paul Mackerras wrote:

On Wed, Feb 28, 2018 at 01:52:37AM +0800, wei.guo.simon@gmail.com wrote:

quoted

From: Simon Guo <redacted>

In both HV/PR KVM, the KVM_SET_ONE_REG/KVM_GET_ONE_REG ioctl should
be able to perform without load vcpu. This patch adds
KVM_SET_ONE_REG/KVM_GET_ONE_REG implementation to async ioctl
function.

Signed-off-by: Simon Guo <redacted>
---
 arch/powerpc/kvm/powerpc.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 7987fa3..6afd004 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c

@@ -1619,6 +1619,19 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp,
 			return -EFAULT;
 		return kvm_vcpu_ioctl_interrupt(vcpu, &irq);
 	}
+
+	if ((ioctl == KVM_SET_ONE_REG) || (ioctl == KVM_GET_ONE_REG)) {
+		struct kvm_one_reg reg;
+
+		if (copy_from_user(&reg, argp, sizeof(reg)))
+			return -EFAULT;
+
+		if (ioctl == KVM_SET_ONE_REG)
+			return kvm_vcpu_ioctl_set_one_reg(vcpu, &reg);
+		else
+			return kvm_vcpu_ioctl_get_one_reg(vcpu, &reg);
+	}
+
 	return -ENOIOCTLCMD;
 }

This seems dangerous to me, since now we can have set/get one_reg
running in parallel with vcpu execution.  Is there a really compelling
reason to do this?  If not I'd rather not make this change.

I will remove this patch.
Thanks,
- Simon