On Wed, Jul 10, 2013 at 01:54:18AM +0200, Andre Przywara wrote:
> 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.przyw...@linaro.org>
> ---
> arch/arm/cpu/armv7/Makefile | 2 +-
> arch/arm/cpu/armv7/nonsec_virt.S | 43
> +++++++++++++++++++++++++++++++++++-----
> arch/arm/cpu/armv7/virt-v7.c | 31 +++++++++++++++++++++++++++++
> arch/arm/include/asm/armv7.h | 9 +++++++--
> arch/arm/lib/bootm.c | 19 +++++++++++++++---
> 5 files changed, 93 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile
> index b59f59e..e5eaa56 100644
> --- a/arch/arm/cpu/armv7/Makefile
> +++ b/arch/arm/cpu/armv7/Makefile
> @@ -36,7 +36,7 @@ ifneq
> ($(CONFIG_AM33XX)$(CONFIG_OMAP44XX)$(CONFIG_OMAP54XX)$(CONFIG_TEGRA)$(CONF
> SOBJS += lowlevel_init.o
> endif
>
> -ifneq ($(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 f9b6b39..895c3b0 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.przyw...@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
> .word 0 /* pad */
> @@ -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
this comment just confuses: either make it intelligent to support an
older compiler or just get rid of these byte encodings. You can always
disassemble the file and lookup the byte code with a modern compiler to
get back to the byte encoding.
> + 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 r1, _smp_pen
> waitloop:
> wfi
> @@ -164,3 +186,14 @@ ENTRY(_nonsec_init)
>
> bx lr
> ENDPROC(_nonsec_init)
> +
> +ENTRY(_switch_to_hyp)
> + mov r0, lr
> + mov r1, sp @ save SVC copy of LR and SP
> + isb
did you find out that this isb is indeed needed? if so, why?
> + hvc #0 @ for older asm: .byte 0x70, 0x00, 0x40, 0xe1
same comment as above?
> + 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 a0d0b34..3645572 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
> @@ -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;
> @@ -92,6 +101,28 @@ static void kick_secondary_cpus(unsigned int gicdaddr)
> writel(1U << 24, gicdaddr + GICD_SGIR);
> }
>
> +enum nonsec_virt_errors armv7_switch_hyp(void)
> +{
> + unsigned int reg;
> +
> + /* check whether we are in HYP mode already */
> + if ((read_cpsr() & 0x1f) == 0x1a)
> + return VIRT_ALREADY_HYP_MODE;
> +
> + /* check whether the CPU supports the virtualization extensions */
> + reg = read_id_pfr1();
> + if ((reg & CPUID_ARM_VIRT_MASK) != 1 << CPUID_ARM_VIRT_SHIFT)
> + return VIRT_ERR_NO_VIRT_EXT;
> +
> + /* call the HYP switching code on this CPU also */
> + _switch_to_hyp();
> +
> + if ((read_cpsr() & 0x1F) != 0x1a)
> + return VIRT_ERR_NOT_HYP_MODE;
> +
> + return NONSEC_VIRT_SUCCESS;
> +}
> +
> enum nonsec_virt_errors armv7_switch_nonsec(void)
> {
> unsigned int reg, ret;
> diff --git a/arch/arm/include/asm/armv7.h b/arch/arm/include/asm/armv7.h
> index f6582a1..baa22fe 100644
> --- a/arch/arm/include/asm/armv7.h
> +++ b/arch/arm/include/asm/armv7.h
> @@ -89,21 +89,26 @@ 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)
>
> enum nonsec_virt_errors {
> NONSEC_VIRT_SUCCESS,
> NONSEC_ERR_NO_SEC_EXT,
> NONSEC_ERR_NO_GIC_ADDRESS,
> NONSEC_ERR_GIC_ADDRESS_ABOVE_4GB,
> + VIRT_ALREADY_HYP_MODE,
> + VIRT_ERR_NO_VIRT_EXT,
> + VIRT_ERR_NOT_HYP_MODE
> };
>
> enum nonsec_virt_errors armv7_switch_nonsec(void);
> +enum nonsec_virt_errors 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 7b0619e..90875b3 100644
> --- a/arch/arm/lib/bootm.c
> +++ b/arch/arm/lib/bootm.c
> @@ -34,7 +34,7 @@
> #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
>
> @@ -192,13 +192,17 @@ __weak void setup_board_tags(struct tag **in_params) {}
>
> static void do_nonsec_virt_switch(void)
> {
> -#ifdef CONFIG_ARMV7_NONSEC
> +#if defined(CONFIG_ARMV7_NONSEC) || defined(CONFIG_ARMV7_VIRT)
> int ret;
>
> ret = armv7_switch_nonsec();
> +#ifdef CONFIG_ARMV7_VIRT
> + if (ret == NONSEC_VIRT_SUCCESS)
> + ret = armv7_switch_hyp();
> +#endif
> switch (ret) {
> case NONSEC_VIRT_SUCCESS:
> - debug("entered non-secure state\n");
> + debug("entered non-secure state or HYP mode\n");
> break;
> case NONSEC_ERR_NO_SEC_EXT:
> printf("nonsec: Security extensions not implemented.\n");
> @@ -209,6 +213,15 @@ static void do_nonsec_virt_switch(void)
> case NONSEC_ERR_GIC_ADDRESS_ABOVE_4GB:
> printf("nonsec: PERIPHBASE is above 4 GB, no access.\n");
> break;
> + case VIRT_ERR_NO_VIRT_EXT:
> + printf("HYP mode: Virtualization extensions not
> implemented.\n");
> + break;
> + case VIRT_ALREADY_HYP_MODE:
> + debug("CPU already in HYP mode\n");
> + break;
> + case VIRT_ERR_NOT_HYP_MODE:
> + printf("HYP mode: switch not successful.\n");
> + break;
> }
> #endif
> }
> --
> 1.7.12.1
>
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