[Xen-devel] [PATCH v4 04/15] x86/HVM: Hardware alternate p2m support detection.

[Ed White <edmund.h.white@xxxxxxxxx>]

As implemented here, only supported on platforms with VMX HAP.

By default this functionality is force-disabled, it can be enabled
by specifying altp2m=1 on the Xen command line.

Signed-off-by: Ed White <edmund.h.white@xxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 docs/misc/xen-command-line.markdown | 7 +++++++
 xen/arch/x86/hvm/hvm.c              | 7 +++++++
 xen/arch/x86/hvm/vmx/vmx.c          | 1 +
 xen/include/asm-x86/hvm/hvm.h       | 9 +++++++++
 4 files changed, 24 insertions(+)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index aa684c0..3391c66 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -139,6 +139,13 @@ mode during S3 resume.
 > Default: `true`
 
 Permit Xen to use superpages when performing memory management.
+ 
+### altp2m (Intel)
+> `= <boolean>`
+
++> Default: `false`
+
+Permit multiple copies of host p2m.
 
 ### apic
 > `= bigsmp | default`
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 535d622..4019658 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -94,6 +94,10 @@ bool_t opt_hvm_fep;
 boolean_param("hvm_fep", opt_hvm_fep);
 #endif
 
+/* Xen command-line option to enable altp2m */
+static bool_t __initdata opt_altp2m_enabled = 0;
+boolean_param("altp2m", opt_altp2m_enabled);
+
 static int cpu_callback(
     struct notifier_block *nfb, unsigned long action, void *hcpu)
 {
@@ -160,6 +164,9 @@ static int __init hvm_enable(void)
     if ( !fns->pvh_supported )
         printk(XENLOG_INFO "HVM: PVH mode not supported on this platform\n");
 
+    if ( !opt_altp2m_enabled )
+        hvm_funcs.altp2m_supported = 0;
+
     /*
      * Allow direct access to the PC debug ports 0x80 and 0xed (they are
      * often used for I/O delays, but the vmexits simply slow things down).
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index fc29b89..07527dd 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1841,6 +1841,7 @@ const struct hvm_function_table * __init start_vmx(void)
     if ( cpu_has_vmx_ept && (cpu_has_vmx_pat || opt_force_ept) )
     {
         vmx_function_table.hap_supported = 1;
+        vmx_function_table.altp2m_supported = 1;
 
         vmx_function_table.hap_capabilities = 0;
 
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 57f9605..c61cfe7 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -94,6 +94,9 @@ struct hvm_function_table {
     /* Necessary hardware support for PVH mode? */
     int pvh_supported;
 
+    /* Necessary hardware support for alternate p2m's? */
+    bool_t altp2m_supported;
+
     /* Indicate HAP capabilities. */
     int hap_capabilities;
 
@@ -509,6 +512,12 @@ bool_t nhvm_vmcx_hap_enabled(struct vcpu *v);
 /* interrupt */
 enum hvm_intblk nhvm_interrupt_blocked(struct vcpu *v);
 
+/* returns true if hardware supports alternate p2m's */
+static inline bool_t hvm_altp2m_supported(void)
+{
+    return hvm_funcs.altp2m_supported;
+}
+
 #ifndef NDEBUG
 /* Permit use of the Forced Emulation Prefix in HVM guests */
 extern bool_t opt_hvm_fep;
-- 
1.9.1


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