Commit 4e903a20 authored by Mukesh Rathor's avatar Mukesh Rathor Committed by Konrad Rzeszutek Wilk
Browse files

xen/pvh: Support ParaVirtualized Hardware extensions (v3). 



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.

We also use introduce the 'XEN_ELFNOTE_SUPPORTED_FEATURES' ELF note to
tell the hypervisor that 'hvm_callback_vector' is what the kernel
needs. We can not put it in 'XEN_ELFNOTE_FEATURES' as older hypervisor
parse fields they don't understand as errors and refuse to load
the kernel. This work-around fixes the problem.

Signed-off-by: default avatarMukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
parent be3e9cf3

arch/x86/xen/Kconfig

+1 −1
Original line number Diff line number Diff line
@@ -53,6 +53,6 @@ config XEN_DEBUG_FS 


config XEN_PVH

	bool "Support for running as a PVH guest"

	depends on X86_64 && XEN && BROKEN

	depends on X86_64 && XEN

	select XEN_PVHVM

	def_bool n

arch/x86/xen/xen-head.S

+24 −1
Original line number Diff line number Diff line
@@ -11,8 +11,28 @@ 
#include <asm/page_types.h>



#include <xen/interface/elfnote.h>

#include <xen/interface/features.h>

#include <asm/xen/interface.h>



#ifdef CONFIG_XEN_PVH

#define PVH_FEATURES_STR  "|writable_descriptor_tables|auto_translated_physmap|supervisor_mode_kernel"

/* Note the lack of 'hvm_callback_vector'. Older hypervisor will

 * balk at this being part of XEN_ELFNOTE_FEATURES, so we put it in

 * XEN_ELFNOTE_SUPPORTED_FEATURES which older hypervisors will ignore.

 */

#define PVH_FEATURES ((1 << XENFEAT_writable_page_tables) | \

		      (1 << XENFEAT_auto_translated_physmap) | \

		      (1 << XENFEAT_supervisor_mode_kernel) | \

		      (1 << XENFEAT_hvm_callback_vector))

/* The XENFEAT_writable_page_tables is not stricly neccessary as we set that

 * up regardless whether this CONFIG option is enabled or not, but it

 * clarifies what the right flags need to be.

 */

#else

#define PVH_FEATURES_STR  ""

#define PVH_FEATURES (0)

#endif



	__INIT

ENTRY(startup_xen)

	cld
@@ -95,7 +115,10 @@ 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_SUPPORTED_FEATURES, .long (PVH_FEATURES) |

						(1 << XENFEAT_writable_page_tables) |

						(1 << XENFEAT_dom0))

	ELFNOTE(Xen, XEN_ELFNOTE_PAE_MODE,       .asciz "yes")

	ELFNOTE(Xen, XEN_ELFNOTE_LOADER,         .asciz "generic")

	ELFNOTE(Xen, XEN_ELFNOTE_L1_MFN_VALID,

include/xen/interface/elfnote.h

+13 −0
Original line number Diff line number Diff line
@@ -140,6 +140,19 @@ 
 */

#define XEN_ELFNOTE_SUSPEND_CANCEL 14



/*

 * The features supported by this kernel (numeric).

 *

 * Other than XEN_ELFNOTE_FEATURES on pre-4.2 Xen, this note allows a

 * kernel to specify support for features that older hypervisors don't

 * know about. The set of features 4.2 and newer hypervisors will

 * consider supported by the kernel is the combination of the sets

 * specified through this and the string note.

 *

 * LEGACY: FEATURES

 */

#define XEN_ELFNOTE_SUPPORTED_FEATURES 17



#endif /* __XEN_PUBLIC_ELFNOTE_H__ */



/*

CRA Git | Maintained and supported by SUSTech CRA and CCSE