x86/KVM/VMX: Add find_msr() helper function

.. to help find the MSR on either the guest or host MSR list.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
CVE-2018-3620
CVE-2018-3646

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 9274197475851a6853a3e46362aaf9428688c3cb..71f97819bb7e67c002ae9bda651f5e94533f3ce5 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2027,9 +2027,20 @@ static void clear_atomic_switch_msr_special(struct vcpu_vmx *vmx,
        vm_exit_controls_clearbit(vmx, exit);
 }
 
+static int find_msr(struct vmx_msrs *m, unsigned int msr)
+{
+       unsigned int i;
+
+       for (i = 0; i < m->nr; ++i) {
+               if (m->val[i].index == msr)
+                       return i;
+       }
+       return -ENOENT;
+}
+
 static void clear_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr)
 {
-       unsigned i;
+       int i;
        struct msr_autoload *m = &vmx->msr_autoload;
 
        switch (msr) {
@@ -2050,11 +2061,8 @@ static void clear_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr)
                }
                break;
        }
-       for (i = 0; i < m->guest.nr; ++i)
-               if (m->guest.val[i].index == msr)
-                       break;
-
-       if (i == m->guest.nr)
+       i = find_msr(&m->guest, msr);
+       if (i < 0)
                return;
        --m->guest.nr;
        --m->host.nr;
@@ -2078,7 +2086,7 @@ static void add_atomic_switch_msr_special(struct vcpu_vmx *vmx,
 static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
                                  u64 guest_val, u64 host_val)
 {
-       unsigned i;
+       int i;
        struct msr_autoload *m = &vmx->msr_autoload;
 
        switch (msr) {
@@ -2113,16 +2121,13 @@ static void add_atomic_switch_msr(struct vcpu_vmx *vmx, unsigned msr,
                wrmsrl(MSR_IA32_PEBS_ENABLE, 0);
        }
 
-       for (i = 0; i < m->guest.nr; ++i)
-               if (m->guest.val[i].index == msr)
-                       break;
-
+       i = find_msr(&m->guest, msr);
        if (i == NR_AUTOLOAD_MSRS) {
                printk_once(KERN_WARNING "Not enough msr switch entries. "
                                "Can't add msr %x\n", msr);
                return;
-       } else if (i == m->guest.nr) {
-               ++m->guest.nr;
+       } else if (i < 0) {
+               i = m->guest.nr++;
                ++m->host.nr;
                vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, m->guest.nr);
                vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, m->host.nr);