tile: support new Tilera hypervisor

The Tilera hypervisor shipped in releases up through MDE 4.1 launches
the client operating system (i.e. Linux) at privilege level 1 (PL1).
Starting with MDE 4.2, as part of the work to enable KVM, the
Tilera hypervisor launches Linux at PL2 instead.

This commit makes the KERNEL_PL option default to 2 for tilegx, while
still saying at 1 for tilepro, which doesn't have an updated hypervisor.
It also explains how and when you might want to choose another value.
In addition, we change a small buglet in the on-chip Ethernet driver,
where we were failing to use the KERNEL_PL constant in an API call.

To make the transition cleaner, this change also provides the updated
hv_init() API for the new hypervisor that supports announcing Linux's
compiled-in PL, so the hypervisor can generate a suitable error in the
case of a mismatched hypervisor and Linux binary.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: stable@vger.linux.org

4 files changed, 44 insertions, 11 deletions

diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 25877aebc685..41a2a0becc18 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -368,11 +368,17 @@ config HARDWALL
 config KERNEL_PL
 	int "Processor protection level for kernel"
 	range 1 2
-	default "1"
+	default 2 if TILEGX
+	default 1 if !TILEGX
 	---help---
-	  This setting determines the processor protection level the
-	  kernel will be built to run at.  Generally you should use
-	  the default value here.
+	  Since MDE 4.2, the Tilera hypervisor runs the kernel
+	  at PL2 by default.  If running under an older hypervisor,
+	  or as a KVM guest, you must run at PL1.  (The current
+	  hypervisor may also be recompiled with "make HV_PL=2" to
+	  allow it to run a kernel at PL1, but clients running at PL1
+	  are not expected to be supported indefinitely.)
+
+	  If you're not sure, don't change the default.
 
 source "arch/tile/gxio/Kconfig"
 
diff --git a/arch/tile/include/hv/hypervisor.h b/arch/tile/include/hv/hypervisor.h
index ccd847e2347f..837dca5328c2 100644
--- a/arch/tile/include/hv/hypervisor.h
+++ b/arch/tile/include/hv/hypervisor.h
@@ -107,7 +107,22 @@
 #define HV_DISPATCH_ENTRY_SIZE 32
 
 /** Version of the hypervisor interface defined by this file */
-#define _HV_VERSION 11
+#define _HV_VERSION 13
+
+/** Last version of the hypervisor interface with old hv_init() ABI.
+ *
+ * The change from version 12 to version 13 corresponds to launching
+ * the client by default at PL2 instead of PL1 (corresponding to the
+ * hv itself running at PL3 instead of PL2).  To make this explicit,
+ * the hv_init() API was also extended so the client can report its
+ * desired PL, resulting in a more helpful failure diagnostic.  If you
+ * call hv_init() with _HV_VERSION_OLD_HV_INIT and omit the client_pl
+ * argument, the hypervisor will assume client_pl = 1.
+ *
+ * Note that this is a deprecated solution and we do not expect to
+ * support clients of the Tilera hypervisor running at PL1 indefinitely.
+ */
+#define _HV_VERSION_OLD_HV_INIT 12
 
 /* Index into hypervisor interface dispatch code blocks.
  *
@@ -377,7 +392,11 @@ typedef int HV_Errno;
 #ifndef __ASSEMBLER__
 
 /** Pass HV_VERSION to hv_init to request this version of the interface. */
-typedef enum { HV_VERSION = _HV_VERSION } HV_VersionNumber;
+typedef enum {
+  HV_VERSION = _HV_VERSION,
+  HV_VERSION_OLD_HV_INIT = _HV_VERSION_OLD_HV_INIT,
+
+} HV_VersionNumber;
 
 /** Initializes the hypervisor.
  *
@@ -385,9 +404,11 @@ typedef enum { HV_VERSION = _HV_VERSION } HV_VersionNumber;
  * that this program expects, typically HV_VERSION.
  * @param chip_num Architecture number of the chip the client was built for.
  * @param chip_rev_num Revision number of the chip the client was built for.
+ * @param client_pl Privilege level the client is built for
+ *   (not required if interface_version_number == HV_VERSION_OLD_HV_INIT).
  */
 void hv_init(HV_VersionNumber interface_version_number,
-             int chip_num, int chip_rev_num);
+             int chip_num, int chip_rev_num, int client_pl);
 
 
 /** Queries we can make for hv_sysconf().
diff --git a/arch/tile/kernel/head_32.S b/arch/tile/kernel/head_32.S
index f71bfeeaf1a9..ac115307e5e4 100644
--- a/arch/tile/kernel/head_32.S
+++ b/arch/tile/kernel/head_32.S
@@ -38,7 +38,7 @@ ENTRY(_start)
 	  movei r2, TILE_CHIP_REV
 	}
 	{
-	  moveli r0, _HV_VERSION
+	  moveli r0, _HV_VERSION_OLD_HV_INIT
 	  jal hv_init
 	}
 	/* Get a reasonable default ASID in r0 */
diff --git a/arch/tile/kernel/head_64.S b/arch/tile/kernel/head_64.S
index f9a2734f7b82..6093964fa5c7 100644
--- a/arch/tile/kernel/head_64.S
+++ b/arch/tile/kernel/head_64.S
@@ -34,13 +34,19 @@
 ENTRY(_start)
 	/* Notify the hypervisor of what version of the API we want */
 	{
+#if KERNEL_PL == 1 && _HV_VERSION == 13
+	  /* Support older hypervisors by asking for API version 12. */
+	  movei r0, _HV_VERSION_OLD_HV_INIT
+#else
+	  movei r0, _HV_VERSION
+#endif
 	  movei r1, TILE_CHIP
-	  movei r2, TILE_CHIP_REV
 	}
 	{
-	  moveli r0, _HV_VERSION
-	  jal hv_init
+	  movei r2, TILE_CHIP_REV
+	  movei r3, KERNEL_PL
 	}
+	jal hv_init
 	/* Get a reasonable default ASID in r0 */
 	{
 	  move r0, zero