[Xen-devel] [v3 01/10] vmx: add new boot parameter to control PML enabling

[Kai Huang <kai.huang@xxxxxxxxxxxxxxx>]

A top level EPT parameter "ept=<options>" and a sub boolean "opt_pml_enabled"
are added to control PML. Other booleans can be further added for any other EPT
related features.

The document description for the new parameter is also added.

Signed-off-by: Kai Huang <kai.huang@xxxxxxxxxxxxxxx>
---
 docs/misc/xen-command-line.markdown | 15 +++++++++++++++
 xen/arch/x86/hvm/vmx/vmcs.c         | 30 ++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index 1dda1f0..4889e27 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -685,6 +685,21 @@ requirement can be relaxed.  This option is particularly 
useful for nested
 virtualization, to allow the L1 hypervisor to use EPT even if the L0 hypervisor
 does not provide VM\_ENTRY\_LOAD\_GUEST\_PAT.
 
+### ept (Intel)
+> `= List of ( pml<boolean> )`
+
+> Default: `false`
+
+Controls EPT related features. Currently only Page Modification Logging (PML) 
is
+the controllable feature as boolean type.
+
+PML is a new hardware feature in Intel's Broadwell Server and further platforms
+which reduces hypervisor overhead of log-dirty mechanism by automatically
+recording GPAs (guest physical addresses) when guest memory gets dirty, and
+therefore significantly reducing number of EPT violation caused by write
+protection of guest memory, which is a necessity to implement log-dirty
+mechanism before PML.
+
 ### gdb
 > `= <baud>[/<clock_hz>][,DPS[,<io-base>[,<irq>[,<port-bdf>[,<bridge-bdf>]]]] 
 > | pci | amt ] `
 
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 63007a9..79efa42 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -64,6 +64,36 @@ integer_param("ple_gap", ple_gap);
 static unsigned int __read_mostly ple_window = 4096;
 integer_param("ple_window", ple_window);
 
+static bool_t __read_mostly opt_pml_enabled = 0;
+
+/*
+ * The 'ept' parameter controls functionalities that depend on, or impact the
+ * EPT mechanism. Optional comma separated value may contain:
+ *
+ *  pml                 Enable PML
+ */
+static void __init parse_ept_param(char *s)
+{
+    char *ss;
+
+    do {
+        bool_t val = !!strncmp(s, "no-", 3);
+        if ( !val )
+            s += 3;
+
+        ss = strchr(s, ',');
+        if ( ss )
+            *ss = '\0';
+
+        if ( !strcmp(s, "pml") )
+            opt_pml_enabled = val;
+
+        s = ss + 1;
+    } while ( ss );
+}
+
+custom_param("ept", parse_ept_param);
+
 /* Dynamic (run-time adjusted) execution control flags. */
 u32 vmx_pin_based_exec_control __read_mostly;
 u32 vmx_cpu_based_exec_control __read_mostly;
-- 
2.1.0


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