diff mbox series

[v3,3/9] powerpc: Introduce FW_FEATURE_ULTRAVISOR

Message ID 20190606173614.32090-4-cclaudio@linux.ibm.com
State Superseded
Headers show
Series kvmppc: Paravirtualize KVM to support ultravisor | expand

Commit Message

Claudio Carvalho June 6, 2019, 5:36 p.m. UTC 
This feature tells if the ultravisor firmware is available to handle
ucalls.

Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
[Device node name to "ibm,ultravisor"]
Signed-off-by: Michael Anderson <andmike@linux.ibm.com>
---
 arch/powerpc/include/asm/firmware.h   |  5 +++--
 arch/powerpc/include/asm/ultravisor.h | 15 +++++++++++++++
 arch/powerpc/kernel/Makefile          |  1 +
 arch/powerpc/kernel/prom.c            |  6 ++++++
 arch/powerpc/kernel/ultravisor.c      | 24 ++++++++++++++++++++++++
 5 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 arch/powerpc/include/asm/ultravisor.h
 create mode 100644 arch/powerpc/kernel/ultravisor.c

Comments

Paul Mackerras June 15, 2019, 7:36 a.m. UTC | #1 
On Thu, Jun 06, 2019 at 02:36:08PM -0300, Claudio Carvalho wrote:
> This feature tells if the ultravisor firmware is available to handle
> ucalls.

Everything in this patch that depends on CONFIG_PPC_UV should just
depend on CONFIG_PPC_POWERNV instead.  The reason is that every host
kernel needs to be able to do the ultracall to set partition table
entry 0, in case it ends up being run on a machine with an ultravisor.
Otherwise we will have the situation where a host kernel may crash
early in boot just because the machine it's booted on happens to have
an ultravisor running.  The crash will be a particularly nasty one
because it will happen before we have probed the machine type and
initialized the console; therefore it will just look like the machine
hangs for no discernable reason.

We also need to think about how to provide a way for petitboot to know
whether the kernel it is booting knows how to do a ucall to set its
partition table entry.  One suggestion would be to modify
vmlinux.lds.S to add a new PT_NOTE entry in the program header of the
binary with (say) a 64-bit doubleword which is a bitmap indicating
capabilities of the binary.  We would define the first bit as
indicating that the kernel knows how to run under an ultravisor.
When running under an ultravisor, petitboot could then look for the
PT_NOTE and the ultravisor-capable bit in it, and if the PT_NOTE is
not there or the bit is zero, put up a dialog warning the user that
the kernel will probably crash early in boot, and asking for explicit
confirmation that the user wants to proceed.

Paul.
Claudio Carvalho July 1, 2019, 2:12 p.m. UTC | #2 
On 6/15/19 4:36 AM, Paul Mackerras wrote:
> On Thu, Jun 06, 2019 at 02:36:08PM -0300, Claudio Carvalho wrote:
>> This feature tells if the ultravisor firmware is available to handle
>> ucalls.
> Everything in this patch that depends on CONFIG_PPC_UV should just
> depend on CONFIG_PPC_POWERNV instead.  The reason is that every host
> kernel needs to be able to do the ultracall to set partition table
> entry 0, in case it ends up being run on a machine with an ultravisor.
> Otherwise we will have the situation where a host kernel may crash
> early in boot just because the machine it's booted on happens to have
> an ultravisor running.  The crash will be a particularly nasty one
> because it will happen before we have probed the machine type and
> initialized the console; therefore it will just look like the machine
> hangs for no discernable reason.

> We also need to think about how to provide a way for petitboot to know
> whether the kernel it is booting knows how to do a ucall to set its
> partition table entry.  One suggestion would be to modify
> vmlinux.lds.S to add a new PT_NOTE entry in the program header of the
> binary with (say) a 64-bit doubleword which is a bitmap indicating
> capabilities of the binary.  We would define the first bit as
> indicating that the kernel knows how to run under an ultravisor.
> When running under an ultravisor, petitboot could then look for the
> PT_NOTE and the ultravisor-capable bit in it, and if the PT_NOTE is
> not there or the bit is zero, put up a dialog warning the user that
> the kernel will probably crash early in boot, and asking for explicit
> confirmation that the user wants to proceed.


I just posted a separated RFC patch for the ELF note.

Thanks, Claudio.


>
> Paul.
>
diff mbox series

Patch

diff --git a/arch/powerpc/include/asm/firmware.h b/arch/powerpc/include/asm/firmware.h
index 00bc42d95679..43b48c4d3ca9 100644
--- a/arch/powerpc/include/asm/firmware.h
+++ b/arch/powerpc/include/asm/firmware.h
@@ -54,6 +54,7 @@ 
 #define FW_FEATURE_DRC_INFO	ASM_CONST(0x0000000800000000)
 #define FW_FEATURE_BLOCK_REMOVE ASM_CONST(0x0000001000000000)
 #define FW_FEATURE_PAPR_SCM 	ASM_CONST(0x0000002000000000)
+#define FW_FEATURE_ULTRAVISOR	ASM_CONST(0x0000004000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -72,9 +73,9 @@  enum {
 		FW_FEATURE_TYPE1_AFFINITY | FW_FEATURE_PRRN |
 		FW_FEATURE_HPT_RESIZE | FW_FEATURE_DRMEM_V2 |
 		FW_FEATURE_DRC_INFO | FW_FEATURE_BLOCK_REMOVE |
-		FW_FEATURE_PAPR_SCM,
+		FW_FEATURE_PAPR_SCM | FW_FEATURE_ULTRAVISOR,
 	FW_FEATURE_PSERIES_ALWAYS = 0,
-	FW_FEATURE_POWERNV_POSSIBLE = FW_FEATURE_OPAL,
+	FW_FEATURE_POWERNV_POSSIBLE = FW_FEATURE_OPAL | FW_FEATURE_ULTRAVISOR,
 	FW_FEATURE_POWERNV_ALWAYS = 0,
 	FW_FEATURE_PS3_POSSIBLE = FW_FEATURE_LPAR | FW_FEATURE_PS3_LV1,
 	FW_FEATURE_PS3_ALWAYS = FW_FEATURE_LPAR | FW_FEATURE_PS3_LV1,
diff --git a/arch/powerpc/include/asm/ultravisor.h b/arch/powerpc/include/asm/ultravisor.h
new file mode 100644
index 000000000000..e5009b0d84ea
--- /dev/null
+++ b/arch/powerpc/include/asm/ultravisor.h
@@ -0,0 +1,15 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Ultravisor definitions
+ *
+ * Copyright 2019, IBM Corporation.
+ *
+ */
+#ifndef _ASM_POWERPC_ULTRAVISOR_H
+#define _ASM_POWERPC_ULTRAVISOR_H
+
+/* Internal functions */
+extern int early_init_dt_scan_ultravisor(unsigned long node, const char *uname,
+					 int depth, void *data);
+
+#endif	/* _ASM_POWERPC_ULTRAVISOR_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 0ea6c4aa3a20..c8ca219e54bf 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -154,6 +154,7 @@  endif
 
 obj-$(CONFIG_EPAPR_PARAVIRT)	+= epapr_paravirt.o epapr_hcalls.o
 obj-$(CONFIG_KVM_GUEST)		+= kvm.o kvm_emul.o
+obj-$(CONFIG_PPC_UV)		+= ultravisor.o
 
 # Disable GCOV, KCOV & sanitizers in odd or sensitive code
 GCOV_PROFILE_prom_init.o := n
diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
index 4221527b082f..8a9a8a319959 100644
--- a/arch/powerpc/kernel/prom.c
+++ b/arch/powerpc/kernel/prom.c
@@ -59,6 +59,7 @@ 
 #include <asm/firmware.h>
 #include <asm/dt_cpu_ftrs.h>
 #include <asm/drmem.h>
+#include <asm/ultravisor.h>
 
 #include <mm/mmu_decl.h>
 
@@ -713,6 +714,11 @@  void __init early_init_devtree(void *params)
 	of_scan_flat_dt(early_init_dt_scan_fw_dump, NULL);
 #endif
 
+#if defined(CONFIG_PPC_UV)
+	/* Scan tree for ultravisor feature */
+	of_scan_flat_dt(early_init_dt_scan_ultravisor, NULL);
+#endif
+
 	/* Retrieve various informations from the /chosen node of the
 	 * device-tree, including the platform type, initrd location and
 	 * size, TCE reserve, and more ...
diff --git a/arch/powerpc/kernel/ultravisor.c b/arch/powerpc/kernel/ultravisor.c
new file mode 100644
index 000000000000..dc6021f63c97
--- /dev/null
+++ b/arch/powerpc/kernel/ultravisor.c
@@ -0,0 +1,24 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Ultravisor high level interfaces
+ *
+ * Copyright 2019, IBM Corporation.
+ *
+ */
+#include <linux/init.h>
+#include <linux/printk.h>
+#include <linux/string.h>
+
+#include <asm/ultravisor.h>
+#include <asm/firmware.h>
+
+int __init early_init_dt_scan_ultravisor(unsigned long node, const char *uname,
+					 int depth, void *data)
+{
+	if (depth != 1 || strcmp(uname, "ibm,ultravisor") != 0)
+		return 0;
+
+	powerpc_firmware_features |= FW_FEATURE_ULTRAVISOR;
+	pr_debug("Ultravisor detected!\n");
+	return 1;
+}