[Xen-changelog] [xen master] tools/libxc: Fix the reported max_leaf values for PV guests

[patchbot@xxxxxxx]

commit 0d045d65c19ac48b31344b566cbf82a0270e6e44
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Mon Jan 9 13:17:01 2017 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Jan 11 15:56:13 2017 +0000

    tools/libxc: Fix the reported max_leaf values for PV guests
    
    When iterating through CPUID leaves to generating a policy, libxc will clip
    itself at the hardcoded maxima, meaning that no data outside of the 
hardcoded
    maxima are provided to Xen (in turn, causing Xen to return zeros if these
    leaves are requested.)
    
    The HVM code also clips the max_leaf data reported to the guest, but the PV
    side didn't.
    
    This results in a PV guest using the emulated CPUID, or via Xen using CPUID
    faulting, to observe a max_leaf higher than the toolstack wants, although 
with
    zeros being returned in the intervening leaves.
    
    Fix the PV side to behave like the HVM side, and clip the max_leaf values in
    leaf 0 and 0x80000000.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxc/xc_cpuid_x86.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tools/libxc/xc_cpuid_x86.c b/tools/libxc/xc_cpuid_x86.c
index e9e3691..b32001b3 100644
--- a/tools/libxc/xc_cpuid_x86.c
+++ b/tools/libxc/xc_cpuid_x86.c
@@ -615,6 +615,11 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
 {
     switch ( input[0] )
     {
+    case 0x00000000:
+        if ( regs[0] > DEF_MAX_BASE )
+            regs[0] = DEF_MAX_BASE;
+        break;
+
     case 0x00000001:
     {
         /* Host topology exposed to PV guest.  Provide host value. */
@@ -655,6 +660,16 @@ static void xc_cpuid_pv_policy(xc_interface *xch,
         xc_cpuid_config_xsave(xch, info, input, regs);
         break;
 
+    case 0x80000000:
+    {
+        unsigned int max = info->vendor == VENDOR_AMD
+            ? DEF_MAX_AMDEXT : DEF_MAX_INTELEXT;
+
+        if ( regs[0] > max )
+            regs[0] = max;
+        break;
+    }
+
     case 0x80000001:
     {
         /* Host topology exposed to PV guest.  Provide host CMP_LEGACY value. 
*/
--
generated by git-patchbot for /home/xen/git/xen.git#master

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