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[RFC,1/6] x86/hyper-v: check for required priviliges in hyperv_init()

Message ID 20171201131321.918-2-vkuznets@redhat.com (mailing list archive)
State New, archived
Headers show

Commit Message

Vitaly Kuznetsov Dec. 1, 2017, 1:13 p.m. UTC 
In hyperv_init() we presume we always have access to VP index and hypercall
MSRs while according to the specification we should check if we're allowed
to access the corresponding MSRs before accessing them.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 arch/x86/hyperv/hv_init.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)
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Patch

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 189a398290db..3ebc7f95e6ca 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -110,12 +110,19 @@  static int hv_cpu_init(unsigned int cpu)
  */
 void hyperv_init(void)
 {
-	u64 guest_id;
+	u64 guest_id, requied_msrs;
 	union hv_x64_msr_hypercall_contents hypercall_msr;
 
 	if (x86_hyper_type != X86_HYPER_MS_HYPERV)
 		return;
 
+	/* Absolutely required MSRs */
+	requied_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE |
+		HV_X64_MSR_VP_INDEX_AVAILABLE;
+
+	if ((ms_hyperv.features & requied_msrs) != requied_msrs)
+		return;
+
 	/* Allocate percpu VP index */
 	hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
 				    GFP_KERNEL);