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Re: [Xen-devel] [PATCH 02/10] VMX: New parameter to control PML enabling





On 03/28/2015 04:42 AM, Andrew Cooper wrote:
On 27/03/15 02:35, Kai Huang wrote:
A top level EPT parameter "ept=<options>" and a sub boolean "pml_enable" are
added to control PML. Other booleans can be further added for any other EPT
related features.

Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
Please patch docs/misc/xen-command-line.markdown as well.  See the
existing "psr" option as a similar example.

Also, as indicated in patch 1, I think patches 1 and 2 need swapping in
the series.

---
  xen/arch/x86/hvm/vmx/vmcs.c | 32 ++++++++++++++++++++++++++++++++
  1 file changed, 32 insertions(+)

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 2f645fe..9b20a4b 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -50,6 +50,16 @@ boolean_param("unrestricted_guest", 
opt_unrestricted_guest_enabled);
  static bool_t __read_mostly opt_apicv_enabled = 1;
  boolean_param("apicv", opt_apicv_enabled);
+static void parse_ept_param(char *s);
+/*
+ * The 'ept' parameter controls functionalities that depend on, or impact the
+ * EPT mechanism. Optional comma separated value may contain:
+ *
+ *  pml                 Enable PML
+ */
+custom_param("ept", parse_ept_param);
It is common to put the custom_param() call below parse_ept_param() so
you don't need to forward-declare the function.  The comment can happily
live at the top of parse_ept_param().
Hi Andrew,

Looks it's better to keep parse_ept_param() below custom_param(), as simply moving parse_ept_param() above custom_param() results in below error (I also changed pml_enable to opt_pml_enabled), as it references opt_pml_enabled variable, which is defined below custom_param(). Actually for "iommu=<options>" parameter, parse_iommu_param() was also placed below custom_param().

What do you think?

vmcs.c: In function ‘parse_ept_param’:
vmcs.c:74:13: error: ‘opt_pml_enabled’ undeclared (first use in this function)
             opt_pml_enabled = val;
             ^
vmcs.c:74:13: note: each undeclared identifier is reported only once for each function it appears in
vmcs.c: At top level:
vmcs.c:81:29: error: ‘opt_pml_enabled’ defined but not used [-Werror=unused-variable]
 static bool_t __read_mostly opt_pml_enabled = 0;

Thanks,
-Kai


+static bool_t __read_mostly pml_enable = 0;
+
  /*
   * These two parameters are used to config the controls for Pause-Loop 
Exiting:
   * ple_gap:    upper bound on the amount of time between two successive
@@ -92,6 +102,28 @@ DEFINE_PER_CPU(bool_t, vmxon);
  static u32 vmcs_revision_id __read_mostly;
  u64 __read_mostly vmx_basic_msr;
+/* Copied from parse_iommu_param */
Not a useful comment, as it is likely to diverge in the future.

+static void parse_ept_param(char *s)
__init

~Andrew

+{
+    char *ss;
+    int val;
+
+    do {
+        val = !!strncmp(s, "no-", 3);
+        if ( !val )
+            s += 3;
+
+        ss = strchr(s, ',');
+        if ( ss )
+            *ss = '\0';
+
+        if ( !strcmp(s, "pml") )
+            pml_enable = val;
+
+        s = ss + 1;
+    } while ( ss );
+}
+
  static void __init vmx_display_features(void)
  {
      int printed = 0;

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