KVM: nVMX: Check GUEST_DR7 on vmentry of nested guests

According to section "Checks on Guest Control Registers, Debug Registers, and
and MSRs" in Intel SDM vol 3C, the following checks are performed on vmentry
of nested guests:

    If the "load debug controls" VM-entry control is 1, bits 63:32 in the DR7
    field must be 0.

In KVM, GUEST_DR7 is set prior to the vmcs02 VM-entry by kvm_set_dr() and the
latter synthesizes a #GP if any bit in the high dword in the former is set.
Hence this field needs to be checked in software.

Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 53ea65070b5a4a33dfd903baf56f12a4f2ab7437..95b3f4306ac2a62ae6e9435fe67e9e0266984ff7 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2887,6 +2887,10 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
            CC(!nested_guest_cr4_valid(vcpu, vmcs12->guest_cr4)))
                return -EINVAL;
 
+       if ((vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS) &&
+           CC(!kvm_dr7_valid(vmcs12->guest_dr7)))
+               return -EINVAL;
+
        if ((vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PAT) &&
            CC(!kvm_pat_valid(vmcs12->guest_ia32_pat)))
                return -EINVAL;

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 48cd4e191b9c549b85bab5a85aee5198ab514225..baf89d4bc653f9894faf9e7dc6aa6ab7ac8f39a9 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1082,7 +1082,7 @@ static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)
        case 5:
                /* fall through */
        default: /* 7 */
-               if (val & 0xffffffff00000000ULL)
+               if (!kvm_dr7_valid(val))
                        return -1; /* #GP */
                vcpu->arch.dr7 = (val & DR7_VOLATILE) | DR7_FIXED_1;
                kvm_update_dr7(vcpu);

diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index e007b61b932a947640206acd6dff249736c6fcab..2d2ff855773b2b4b0b9de7b95504d27e271db6e4 100644 (file)
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -357,6 +357,12 @@ static inline bool kvm_pat_valid(u64 data)
        return (data | ((data & 0x0202020202020202ull) << 1)) == data;
 }
 
+static inline bool kvm_dr7_valid(unsigned long data)
+{
+       /* Bits [63:32] are reserved */
+       return !(data >> 32);
+}
+
 void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu);
 void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu);
 u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu);