commit f5c43bd4218c0d7bd65b010fd080cd6edeaeb4c8
author James Hogan <james.hogan@imgtec.com> Wed Jun 15 19:29:49 2016 +0100
committer Paolo Bonzini <pbonzini@redhat.com> Wed Jun 15 23:58:24 2016 +0200
tree 8b8311296fef7adc91a2f48b97a0dc99f11fb746
parent cc68d22f9727d02c1d981d27c11389fd9413e419

MIPS: KVM: Make KVM_GET_REG_LIST dynamic

Make the implementation of KVM_GET_REG_LIST more dynamic so that only
the subset of registers actually available can be exposed to user mode.
This is important for VZ where some of the guest register state may not
be possible to prevent the guest from accessing, therefore the user
process may need to be aware of the state even if it doesn't understand
what the state is for.

This also allows different MIPS KVM implementations to provide different
registers to one another, by way of new num_regs(vcpu) and
copy_reg_indices(vcpu, indices) callback functions, currently just
stubbed for trap & emulate.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/kvm/mips.c

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index fe82f33..2c4709a 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -538,6 +538,26 @@
 	KVM_REG_MIPS_COUNT_HZ,
 };
 
+static unsigned long kvm_mips_num_regs(struct kvm_vcpu *vcpu)
+{
+	unsigned long ret;
+
+	ret = ARRAY_SIZE(kvm_mips_get_one_regs);
+	ret += kvm_mips_callbacks->num_regs(vcpu);
+
+	return ret;
+}
+
+static int kvm_mips_copy_reg_indices(struct kvm_vcpu *vcpu, u64 __user *indices)
+{
+	if (copy_to_user(indices, kvm_mips_get_one_regs,
+			 sizeof(kvm_mips_get_one_regs)))
+		return -EFAULT;
+	indices += ARRAY_SIZE(kvm_mips_get_one_regs);
+
+	return kvm_mips_callbacks->copy_reg_indices(vcpu, indices);
+}
+
 static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
 			    const struct kvm_one_reg *reg)
 {
@@ -908,23 +928,18 @@
 	}
 	case KVM_GET_REG_LIST: {
 		struct kvm_reg_list __user *user_list = argp;
-		u64 __user *reg_dest;
 		struct kvm_reg_list reg_list;
 		unsigned n;
 
 		if (copy_from_user(&reg_list, user_list, sizeof(reg_list)))
 			return -EFAULT;
 		n = reg_list.n;
-		reg_list.n = ARRAY_SIZE(kvm_mips_get_one_regs);
+		reg_list.n = kvm_mips_num_regs(vcpu);
 		if (copy_to_user(user_list, &reg_list, sizeof(reg_list)))
 			return -EFAULT;
 		if (n < reg_list.n)
 			return -E2BIG;
-		reg_dest = user_list->reg;
-		if (copy_to_user(reg_dest, kvm_mips_get_one_regs,
-				 sizeof(kvm_mips_get_one_regs)))
-			return -EFAULT;
-		return 0;
+		return kvm_mips_copy_reg_indices(vcpu, user_list->reg);
 	}
 	case KVM_NMI:
 		/* Treat the NMI as a CPU reset */