[Xen-devel] [PATCH v4 1/5] x86: allow reading MSR_IA32_TSC with XENPF_resource_op

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

Memory bandwidth monitoring requires timestamp returned along with the
monitoring counter to verify the correctness of the counter value.
Allow MSR_IA32_TSC to be read and increase RESOURCE_ACCESS_MAX_ENTRIES
to 3.

Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
---
 xen/arch/x86/platform_hypercall.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/platform_hypercall.c 
b/xen/arch/x86/platform_hypercall.c
index 32f39b2..e80b857 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -61,14 +61,14 @@ long cpu_down_helper(void *data);
 long core_parking_helper(void *data);
 uint32_t get_cur_idle_nums(void);
 
-#define RESOURCE_ACCESS_MAX_ENTRIES 2
+#define RESOURCE_ACCESS_MAX_ENTRIES 3
 struct xen_resource_access {
     unsigned int nr_done;
     unsigned int nr_entries;
     xenpf_resource_entry_t *entries;
 };
 
-static bool_t allow_access_msr(unsigned int msr)
+static bool_t allow_access_msr(unsigned int msr, unsigned int cmd)
 {
     switch ( msr )
     {
@@ -76,6 +76,8 @@ static bool_t allow_access_msr(unsigned int msr)
     case MSR_IA32_CMT_EVTSEL:
     case MSR_IA32_CMT_CTR:
         return 1;
+    case MSR_IA32_TSC:
+        return cmd == XEN_RESOURCE_OP_MSR_READ;
     }
 
     return 0;
@@ -102,7 +104,7 @@ static void check_resource_access(struct 
xen_resource_access *ra)
         case XEN_RESOURCE_OP_MSR_WRITE:
             if ( entry->idx >> 32 )
                 ret = -EINVAL;
-            else if ( !allow_access_msr(entry->idx) )
+            else if ( !allow_access_msr(entry->idx, entry->u.cmd) )
                 ret = -EACCES;
             break;
         default:
-- 
1.9.1


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