[U-Boot] [PATCH v2 6/7] ARM: extend non-secure switch to also go into HYP mode

Andre Przywara
2013-06-13T11:01:12Z

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 adds and adjusts some error reporting.

Signed-off-by: Andre Przywara <andre.przywara@linaro.org>
---
arch/arm/cpu/armv7/nonsec_virt.S | 31 ++++++++++++++++++++++++++++---
arch/arm/include/asm/armv7.h | 7 +++++--
arch/arm/lib/bootm.c | 14 ++++++++++----
arch/arm/lib/virt-v7.c | 27 ++++++++++++++++++++++-----
4 files changed, 65 insertions(+), 14 deletions(-)

diff --git a/arch/arm/cpu/armv7/nonsec_virt.S b/arch/arm/cpu/armv7/nonsec_virt.S
index 919f6e9..950da6f 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>
*
@@ -26,14 +26,14 @@
#include <asm/gic.h>
#include <asm/armv7.h>

-/* the vector table for secure state */
+/* the vector table for secure state and HYP mode */
_secure_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
.word 0 /* pad */
@@ -50,10 +50,23 @@ _secure_monitor:
bic r1, r1, #0x4e @ clear IRQ, FIQ, EA, nET bits
orr r1, r1, #0x31 @ enable NS, AW, FW bits

+ 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
+
mcr p15, 0, r1, c1, c1, 0 @ write SCR (with NS bit set)

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

+_hyp_trap:
+ .byte 0x00, 0xe3, 0x0e, 0xe1 @ mrs lr, elr_hyp
+ 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
@@ -69,6 +82,7 @@ _smp_pen:
mcr p15, 0, r1, c12, c0, 0 @ set VBAR

bl _nonsec_init
+ bl _hyp_init

ldr r1, [r3, #0x0c] @ read GICD acknowledge
str r1, [r3, #0x10] @ write GICD EOI
@@ -145,3 +159,14 @@ _nonsec_init:
str r1, [r2] @ allow private interrupts

bx lr
+
+.globl _hyp_init
+_hyp_init:
+ mov r2, lr
+ mov r3, sp @ save SVC copy of LR and SP
+ isb
+ .byte 0x70, 0x00, 0x40, 0xe1 @ hvc #0
+ mov sp, r3
+ mov lr, r2 @ fix HYP mode banked LR and SP
+
+ bx lr
diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
index 04545b9..8c3a85e 100644
--- a/arch/arm/include/asm/armv7.h
+++ b/arch/arm/include/asm/armv7.h
@@ -89,15 +89,18 @@ void v7_outer_cache_inval_range(u32 start, u32 end);

#ifdef CONFIG_ARMV7_VIRT

-#define HYP_ERR_NO_SEC_EXT 2
+#define HYP_ERR_ALREADY_HYP_MODE 1
+#define HYP_ERR_NO_VIRT_EXT 2
#define HYP_ERR_NO_GIC_ADDRESS 3
#define HYP_ERR_GIC_ADDRESS_ABOVE_4GB 4
+#define HYP_ERR_NOT_HYP_MODE 5

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

/* defined in cpu/armv7/nonsec_virt.S */
void _nonsec_init(void);
void _smp_pen(void);
+void _hyp_init(void);
#endif /* CONFIG_ARMV7_VIRT */

#endif /* ! __ASSEMBLY__ */
diff --git a/arch/arm/lib/bootm.c b/arch/arm/lib/bootm.c
index 8251a89..7edd84d 100644
--- a/arch/arm/lib/bootm.c
+++ b/arch/arm/lib/bootm.c
@@ -227,12 +227,15 @@ static void boot_prep_linux(bootm_headers_t *images)
hang();
}
#ifdef CONFIG_ARMV7_VIRT
- switch (armv7_switch_nonsec()) {
+ switch (armv7_switch_hyp()) {
case 0:
- debug("entered non-secure state\n");
+ debug("entered HYP mode\n");
break;
- case HYP_ERR_NO_SEC_EXT:
- printf("HYP mode: Security extensions not implemented.\n");
+ case HYP_ERR_ALREADY_HYP_MODE:
+ debug("CPU already in HYP mode\n");
+ break;
+ case HYP_ERR_NO_VIRT_EXT:
+ printf("HYP mode: Virtualization extensions not implemented.\n");
break;
case HYP_ERR_NO_GIC_ADDRESS:
printf("HYP mode: could not determine GIC address.\n");
@@ -240,6 +243,9 @@ static void boot_prep_linux(bootm_headers_t *images)
case HYP_ERR_GIC_ADDRESS_ABOVE_4GB:
printf("HYP mode: PERIPHBASE is above 4 GB, cannot access this.\n");
break;
+ case HYP_ERR_NOT_HYP_MODE:
+ printf("HYP mode: switch not successful.\n");
+ break;
}
#endif
}
diff --git a/arch/arm/lib/virt-v7.c b/arch/arm/lib/virt-v7.c
index 6946e4d..1e206b9 100644
--- a/arch/arm/lib/virt-v7.c
+++ b/arch/arm/lib/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
@@ -29,6 +30,14 @@
#include <asm/gic.h>
#include <asm/io.h>

+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;
@@ -110,16 +119,20 @@ static void kick_secondary_cpus(char *gicdptr)
writel(1U << 24, &gicdptr[GICD_SGIR]);
}

-int armv7_switch_nonsec(void)
+int armv7_switch_hyp(void)
{
unsigned int reg, ret;
char *gicdptr;
unsigned itlinesnr, i;

- /* check whether the CPU supports the security extensions */
+ /* check whether we are in HYP mode already */
+ if ((read_cpsr() & 0x1f) == 0x1a)
+ return HYP_ERR_ALREADY_HYP_MODE;
+
+ /* check whether the CPU supports the virtualization extensions */
reg = read_id_pfr1();
- if ((reg & 0xF0) == 0)
- return HYP_ERR_NO_SEC_EXT;
+ if ((reg & CPUID_ARM_VIRT_MASK) != 1 << CPUID_ARM_VIRT_SHIFT)
+ return HYP_ERR_NO_VIRT_EXT;

set_generic_timer_frequency();

@@ -147,8 +160,12 @@ int armv7_switch_nonsec(void)

kick_secondary_cpus(gicdptr);

- /* call the non-sec switching code on this CPU also */
+ /* call the HYP switching code on this CPU also */
_nonsec_init();
+ _hyp_init();
+
+ if ((read_cpsr() & 0x1F) != 0x1a)
+ return HYP_ERR_NOT_HYP_MODE;

return 0;
}
--
1.7.12.1