Re: [Xen-devel] [PATCH v2 04/10] x86/cpuid: Handle leaf 0x4 in guest_cpuid()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 13/03/17 13:05, Jan Beulich wrote:
>>>> On 13.03.17 at 13:51, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 13/03/17 12:03, Jan Beulich wrote:
>>>>>> On 10.03.17 at 17:27, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>> @@ -242,6 +243,25 @@ static void __init calculate_raw_policy(void)
>>>>          cpuid_leaf(i, &p->basic.raw[i]);
>>>>      }
>>>>  
>>>> +    if ( p->basic.max_leaf >= 4 )
>>>> +    {
>>>> +        for ( i = 0; i < ARRAY_SIZE(p->cache.raw); ++i )
>>>> +        {
>>>> +            cpuid_count_leaf(4, i, &p->cache.raw[i]);
>>>> +
>>>> +            if ( p->cache.subleaf[i].type == 0 )
>>>> +                break;
>>>> +        }
>>>> +
>>>> +        /*
>>>> +         * The choice of CPUID_GUEST_NR_CACHE is arbitrary.  It is 
>>>> expected
>>>> +         * that it will eventually need increasing for future hardware.
>>>> +         */
>>>> +        if ( i == ARRAY_SIZE(p->cache.raw) )
>>>> +            printk(XENLOG_WARNING
>>>> +                   "CPUID: Insufficient Leaf 4 space for this 
>>>> hardware\n");
>>>> +    }
>>> As expressed before (perhaps in the context of another patch),
>>> the warning may be logged prematurely, which I'd prefer to be
>>> avoided.
>> How would you like it then?  You previously indicated that it probably
>> want a problem leaving it like this, which is why I did.
> And I continue to be of that opinion: It's probably not a problem to
> leave it as is (hence the R-b), but I'd prefer if the warning was only
> issued when we actually can't fit at least one sub-leaf.

Is this delta ok?

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index b70fc0b..7caf6af 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -251,10 +251,17 @@ static void __init calculate_raw_policy(void)
     {
         for ( i = 0; i < ARRAY_SIZE(p->cache.raw); ++i )
         {
-            cpuid_count_leaf(4, i, &p->cache.raw[i]);
+            union {
+                struct cpuid_leaf l;
+                struct cpuid_cache_leaf c;
+            } u;
 
-            if ( p->cache.subleaf[i].type == 0 )
+            cpuid_count_leaf(4, i, &u.l);
+
+            if ( u.c.type == 0 )
                 break;
+
+            p->cache.subleaf[i] = u.c;
         }
 
         /*
diff --git a/xen/include/asm-x86/cpuid.h b/xen/include/asm-x86/cpuid.h
index 816f06d..ac25908 100644
--- a/xen/include/asm-x86/cpuid.h
+++ b/xen/include/asm-x86/cpuid.h
@@ -118,7 +118,7 @@ struct cpuid_policy
     /* Structured cache leaf: 0x00000004[xx] */
     union {
         struct cpuid_leaf raw[CPUID_GUEST_NR_CACHE];
-        struct {
+        struct cpuid_cache_leaf {
             uint32_t type:5,
                 :27, :32, :32, :32;
         } subleaf[CPUID_GUEST_NR_CACHE];


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