[PATCH v11 12/12] xen/pvh: Support ParaVirtualized Hardware extensions.

[Konrad Rzeszutek Wilk]

From: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>

PVH allows PV linux guest to utilize hardware extended capabilities,
such as running MMU updates in a HVM container.

The Xen side defines PVH as (from docs/misc/pvh-readme.txt,
with modifications):

"* the guest uses auto translate:
 - p2m is managed by Xen
 - pagetables are owned by the guest
 - mmu_update hypercall not available
* it uses event callback and not vlapic emulation,
* IDT is native, so set_trap_table hcall is also N/A for a PVH guest.

For a full list of hcalls supported for PVH, see pvh_hypercall64_table
in arch/x86/hvm/hvm.c in xen.  From the ABI prespective, it's mostly a
PV guest with auto translate, although it does use hvm_op for setting
callback vector."

Use .ascii and .asciz to define xen feature string. Note, the PVH
string must be in a single line (not multiple lines with \) to keep the
assembler from putting null char after each string before \.
This patch allows it to be configured and enabled.

Lastly remove some of the scaffolding.

Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/Kconfig    | 8 ++++++++
 arch/x86/xen/xen-head.S | 8 +++++++-
 include/xen/xen.h       | 3 +--
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index 1a3c765..161cc34 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -51,3 +51,11 @@ config XEN_DEBUG_FS
 	  Enable statistics output and various tuning options in debugfs.
 	  Enabling this option may incur a significant performance overhead.
 
+config XEN_PVH
+	bool "Support for running as a PVH guest"
+	depends on X86_64 && XEN && XEN_PVHVM
+	default n
+	help
+	   This option enables support for running as a PVH guest (PV guest
+	   using hardware extensions) under a suitably capable hypervisor.
+	   If unsure, say N.
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 7faed58..56f42c0 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -13,6 +13,12 @@
 #include <xen/interface/elfnote.h>
 #include <asm/xen/interface.h>
 
+#ifdef CONFIG_XEN_PVH
+#define PVH_FEATURES_STR  "|writable_descriptor_tables|auto_translated_physmap|supervisor_mode_kernel|hvm_callback_vector"
+#else
+#define PVH_FEATURES_STR  ""
+#endif
+
 	__INIT
 ENTRY(startup_xen)
 	cld
@@ -95,7 +101,7 @@ NEXT_HYPERCALL(arch_6)
 #endif
 	ELFNOTE(Xen, XEN_ELFNOTE_ENTRY,          _ASM_PTR startup_xen)
 	ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, _ASM_PTR hypercall_page)
-	ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .asciz "!writable_page_tables|pae_pgdir_above_4gb")
+	ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .ascii "!writable_page_tables|pae_pgdir_above_4gb"; .asciz PVH_FEATURES_STR)
 	ELFNOTE(Xen, XEN_ELFNOTE_PAE_MODE,       .asciz "yes")
 	ELFNOTE(Xen, XEN_ELFNOTE_LOADER,         .asciz "generic")
 	ELFNOTE(Xen, XEN_ELFNOTE_L1_MFN_VALID,
diff --git a/include/xen/xen.h b/include/xen/xen.h
index 1d6a237..a248002 100644
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -29,8 +29,7 @@ extern enum xen_domain_type xen_domain_type;
 #define xen_initial_domain()	(0)
 #endif	/* CONFIG_XEN_DOM0 */
 
-#ifdef CONFIG_XEN_PVHVM
-/* Temporarily under XEN_PVHVM, but will be under CONFIG_XEN_PVH */
+#ifdef CONFIG_XEN_PVH
 #include <xen/features.h>
 #define xen_pvh_domain() (xen_pv_domain() && \
 			  xen_feature(XENFEAT_auto_translated_physmap) && \
-- 
1.8.3.1

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