KVM: SVM: Introduce direct access msr list

This patch introduces a list with all msrs a guest might
have direct access to and changes the svm_vcpu_init_msrpm
function to use this list.
It also adds a check to set_msr_interception which triggers
a warning if a developer changes a msr intercept that is not
in the list.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 429a24435c6d29231e4628d284032e30195db7ff..a079550d3886fbe54cc010858024752a815f50d0 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -119,6 +119,27 @@ struct vcpu_svm {
 
 #define MSR_INVALID                    0xffffffffU
 
+static struct svm_direct_access_msrs {
+       u32 index;   /* Index of the MSR */
+       bool always; /* True if intercept is always on */
+} direct_access_msrs[] = {
+       { .index = MSR_K6_STAR,                         .always = true  },
+       { .index = MSR_IA32_SYSENTER_CS,                .always = true  },
+#ifdef CONFIG_X86_64
+       { .index = MSR_GS_BASE,                         .always = true  },
+       { .index = MSR_FS_BASE,                         .always = true  },
+       { .index = MSR_KERNEL_GS_BASE,                  .always = true  },
+       { .index = MSR_LSTAR,                           .always = true  },
+       { .index = MSR_CSTAR,                           .always = true  },
+       { .index = MSR_SYSCALL_MASK,                    .always = true  },
+#endif
+       { .index = MSR_IA32_LASTBRANCHFROMIP,           .always = false },
+       { .index = MSR_IA32_LASTBRANCHTOIP,             .always = false },
+       { .index = MSR_IA32_LASTINTFROMIP,              .always = false },
+       { .index = MSR_IA32_LASTINTTOIP,                .always = false },
+       { .index = MSR_INVALID,                         .always = false },
+};
+
 /* enable NPT for AMD64 and X86 with PAE */
 #if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
 static bool npt_enabled = true;
@@ -438,6 +459,17 @@ err_1:
 
 }
 
+static bool valid_msr_intercept(u32 index)
+{
+       int i;
+
+       for (i = 0; direct_access_msrs[i].index != MSR_INVALID; i++)
+               if (direct_access_msrs[i].index == index)
+                       return true;
+
+       return false;
+}
+
 static void set_msr_interception(u32 *msrpm, unsigned msr,
                                 int read, int write)
 {
@@ -445,6 +477,12 @@ static void set_msr_interception(u32 *msrpm, unsigned msr,
        unsigned long tmp;
        u32 offset;
 
+       /*
+        * If this warning triggers extend the direct_access_msrs list at the
+        * beginning of the file
+        */
+       WARN_ON(!valid_msr_intercept(msr));
+
        offset    = svm_msrpm_offset(msr);
        bit_read  = 2 * (msr & 0x0f);
        bit_write = 2 * (msr & 0x0f) + 1;
@@ -460,18 +498,16 @@ static void set_msr_interception(u32 *msrpm, unsigned msr,
 
 static void svm_vcpu_init_msrpm(u32 *msrpm)
 {
+       int i;
+
        memset(msrpm, 0xff, PAGE_SIZE * (1 << MSRPM_ALLOC_ORDER));
 
-#ifdef CONFIG_X86_64
-       set_msr_interception(msrpm, MSR_GS_BASE, 1, 1);
-       set_msr_interception(msrpm, MSR_FS_BASE, 1, 1);
-       set_msr_interception(msrpm, MSR_KERNEL_GS_BASE, 1, 1);
-       set_msr_interception(msrpm, MSR_LSTAR, 1, 1);
-       set_msr_interception(msrpm, MSR_CSTAR, 1, 1);
-       set_msr_interception(msrpm, MSR_SYSCALL_MASK, 1, 1);
-#endif
-       set_msr_interception(msrpm, MSR_K6_STAR, 1, 1);
-       set_msr_interception(msrpm, MSR_IA32_SYSENTER_CS, 1, 1);
+       for (i = 0; direct_access_msrs[i].index != MSR_INVALID; i++) {
+               if (!direct_access_msrs[i].always)
+                       continue;
+
+               set_msr_interception(msrpm, direct_access_msrs[i].index, 1, 1);
+       }
 }
 
 static void svm_enable_lbrv(struct vcpu_svm *svm)