[U-Boot] [PATCH v5 7/8] ARM: extend non-secure switch to also go into HYP mode

Andre Przywara
2013-09-19T16:06:45Z

For the KVM and XEN hypervisors to be usable, we need to enter the
kernel in HYP mode. Now that we already are in non-secure state,
HYP mode switching is within short reach.

While doing the non-secure switch, we have to enable the HVC
instruction and setup the HYP mode HVBAR (while still secure).

The actual switch is done by dropping back from a HYP mode handler
without actually leaving HYP mode, so we introduce a new handler
routine in our new secure exception vector table.

In the assembly switching routine we save and restore the banked LR
and SP registers around the hypercall to do the actual HYP mode
switch.

The C routine first checks whether we are in HYP mode already and
also whether the virtualization extensions are available. It also
checks whether the HYP mode switch was finally successful.
The bootm command part only calls the new function after the
non-secure switch.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
---
arch/arm/cpu/armv7/Makefile | 2 +-
arch/arm/cpu/armv7/nonsec_virt.S | 43 +++++++++++++++++++++++++++++++++++-----
arch/arm/cpu/armv7/virt-v7.c | 37 ++++++++++++++++++++++++++++++++++
arch/arm/include/asm/armv7.h | 6 ++++--
arch/arm/lib/bootm.c | 7 ++++++-
5 files changed, 86 insertions(+), 9 deletions(-)

Changes:
v3..v4: w/s fixes, embed error output
v4..v5: none

diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile
index 024c28b..ee4b021 100644
--- a/arch/arm/cpu/armv7/Makefile
+++ b/arch/arm/cpu/armv7/Makefile
@@ -20,7 +20,7 @@ ifneq ($(CONFIG_AM43XX)$(CONFIG_AM33XX)$(CONFIG_OMAP44XX)$(CONFIG_OMAP54XX)$(CON
SOBJS += lowlevel_init.o
endif

-ifneq ($(CONFIG_ARMV7_NONSEC),)
+ifneq ($(CONFIG_ARMV7_NONSEC)$(CONFIG_ARMV7_VIRT),)
SOBJS += nonsec_virt.o
COBJS += virt-v7.o
endif
diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
index cbee8f7..358348f 100644
--- a/arch/arm/cpu/armv7/nonsec_virt.S
+++ b/arch/arm/cpu/armv7/nonsec_virt.S
@@ -1,5 +1,5 @@
/*
- * code for switching cores into non-secure state
+ * code for switching cores into non-secure state and into HYP mode
*
* Copyright (c) 2013 Andre Przywara <andre.przywara@linaro.org>
*
@@ -28,15 +28,16 @@
#include <asm/armv7.h>

.arch_extension sec
+.arch_extension virt

-/* the vector table for secure state */
+/* the vector table for secure state and HYP mode */
_monitor_vectors:
.word 0 /* reset */
.word 0 /* undef */
adr pc, _secure_monitor
.word 0
.word 0
- .word 0
+ adr pc, _hyp_trap
.word 0
.word 0

@@ -53,10 +54,27 @@ _secure_monitor:
bic r1, r1, #0x4e @ clear IRQ, FIQ, EA, nET bits
orr r1, r1, #0x31 @ enable NS, AW, FW bits

+#ifdef CONFIG_ARMV7_VIRT
+ mrc p15, 0, r0, c0, c1, 1 @ read ID_PFR1
+ and r0, r0, #CPUID_ARM_VIRT_MASK @ mask virtualization bits
+ cmp r0, #(1 << CPUID_ARM_VIRT_SHIFT)
+ orreq r1, r1, #0x100 @ allow HVC instruction
+#endif
+
mcr p15, 0, r1, c1, c1, 0 @ write SCR (with NS bit set)

+#ifdef CONFIG_ARMV7_VIRT
+ mrceq p15, 0, r0, c12, c0, 1 @ get MVBAR value
+ mcreq p15, 4, r0, c12, c0, 0 @ write HVBAR
+#endif
+
movs pc, lr @ return to non-secure SVC

+_hyp_trap:
+ mrs lr, elr_hyp @ for older asm: .byte 0x00, 0xe3, 0x0e, 0xe1
+ mov pc, lr @ do no switch modes, but
+ @ return to caller
+
/*
* Secondary CPUs start here and call the code for the core specific parts
* of the non-secure and HYP mode transition. The GIC distributor specific
@@ -71,9 +89,13 @@ ENTRY(_smp_pen)
mcr p15, 0, r1, c12, c0, 0 @ set VBAR

bl _nonsec_init
+ mov r12, r0 @ save GICC address
+#ifdef CONFIG_ARMV7_VIRT
+ bl _switch_to_hyp
+#endif

- ldr r1, [r0, #GICC_IAR] @ acknowledge IPI
- str r1, [r0, #GICC_EOIR] @ signal end of interrupt
+ ldr r1, [r12, #GICC_IAR] @ acknowledge IPI
+ str r1, [r12, #GICC_EOIR] @ signal end of interrupt

adr r0, _smp_pen @ do not use this address again
b smp_waitloop @ wait for IPIs, board specific
@@ -173,3 +195,14 @@ ENTRY(smp_waitloop)
ENDPROC(smp_waitloop)
.weak smp_waitloop
#endif
+
+ENTRY(_switch_to_hyp)
+ mov r0, lr
+ mov r1, sp @ save SVC copy of LR and SP
+ isb
+ hvc #0 @ for older asm: .byte 0x70, 0x00, 0x40, 0xe1
+ mov sp, r1
+ mov lr, r0 @ restore SVC copy of LR and SP
+
+ bx lr
+ENDPROC(_switch_to_hyp)
diff --git a/arch/arm/cpu/armv7/virt-v7.c b/arch/arm/cpu/armv7/virt-v7.c
index a0b8742..6de7fe7 100644
--- a/arch/arm/cpu/armv7/virt-v7.c
+++ b/arch/arm/cpu/armv7/virt-v7.c
@@ -3,6 +3,7 @@
* Andre Przywara, Linaro
*
* Routines to transition ARMv7 processors from secure into non-secure state
+ * and from non-secure SVC into HYP mode
* needed to enable ARMv7 virtualization for current hypervisors
*
* See file CREDITS for list of people who contributed to this
@@ -31,6 +32,14 @@

unsigned long gic_dist_addr;

+static unsigned int read_cpsr(void)
+{
+ unsigned int reg;
+
+ asm volatile ("mrs %0, cpsr\n" : "=r" (reg));
+ return reg;
+}
+
static unsigned int read_id_pfr1(void)
{
unsigned int reg;
@@ -90,6 +99,34 @@ void __weak smp_kick_all_cpus(void)
kick_secondary_cpus_gic(gic_dist_addr);
}

+int armv7_switch_hyp(void)
+{
+ unsigned int reg;
+
+ /* check whether we are in HYP mode already */
+ if ((read_cpsr() & 0x1f) == 0x1a) {
+ debug("CPU already in HYP mode\n");
+ return 0;
+ }
+
+ /* check whether the CPU supports the virtualization extensions */
+ reg = read_id_pfr1();
+ if ((reg & CPUID_ARM_VIRT_MASK) != 1 << CPUID_ARM_VIRT_SHIFT) {
+ printf("HYP mode: Virtualization extensions not implemented.\n");
+ return -1;
+ }
+
+ /* call the HYP switching code on this CPU also */
+ _switch_to_hyp();
+
+ if ((read_cpsr() & 0x1F) != 0x1a) {
+ printf("HYP mode: switch not successful.\n");
+ return -1;
+ }
+
+ return 0;
+}
+
int armv7_switch_nonsec(void)
{
unsigned int reg;
diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
index 2efd4bc..395444e 100644
--- a/arch/arm/include/asm/armv7.h
+++ b/arch/arm/include/asm/armv7.h
@@ -76,14 +76,16 @@ void v7_outer_cache_inval_all(void);
void v7_outer_cache_flush_range(u32 start, u32 end);
void v7_outer_cache_inval_range(u32 start, u32 end);

-#ifdef CONFIG_ARMV7_NONSEC
+#if defined(CONFIG_ARMV7_NONSEC) || defined(CONFIG_ARMV7_VIRT)

int armv7_switch_nonsec(void);
+int armv7_switch_hyp(void);

/* defined in assembly file */
unsigned int _nonsec_init(void);
void _smp_pen(void);
-#endif /* CONFIG_ARMV7_NONSEC */
+void _switch_to_hyp(void);
+#endif /* CONFIG_ARMV7_NONSEC || CONFIG_ARMV7_VIRT */

#endif /* ! __ASSEMBLY__ */

diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
index b3a961a..f476a89 100644
--- a/arch/arm/lib/bootm.c
+++ b/arch/arm/lib/bootm.c
@@ -22,7 +22,7 @@
#include <asm/bootm.h>
#include <linux/compiler.h>

-#ifdef CONFIG_ARMV7_NONSEC
+#if defined(CONFIG_ARMV7_NONSEC) || defined(CONFIG_ARMV7_VIRT)
#include <asm/armv7.h>
#endif

@@ -189,8 +189,13 @@ static void do_nonsec_virt_switch(void)
{
#if defined(CONFIG_ARMV7_NONSEC) || defined(CONFIG_ARMV7_VIRT)
if (armv7_switch_nonsec() == 0)
+#ifdef CONFIG_ARMV7_VIRT
+ if (armv7_switch_hyp() == 0)
+ debug("entered HYP mode\n");
+#else
debug("entered non-secure state\n");
#endif
+#endif
}

/* Subcommand: PREP */
--
1.7.12.1