[U-Boot] [PATCH v4 1/1] efi_loader: PSCI reset and shutdown

Heinrich Schuchardt xypron.glpk at gmx.de
Wed Oct 17 18:06:32 UTC 2018


On 10/17/2018 07:37 PM, Alexander Graf wrote:
> 
> 
> On 17.10.18 19:05, Heinrich Schuchardt wrote:
>> When an operating system started via bootefi tries to reset or power off
>> this is done by calling the EFI runtime ResetSystem(). On most ARMv8 system
>> the actual reset relies on PSCI. Depending on whether the PSCI firmware
>> resides the hypervisor (EL2) or in the secure monitor (EL3) either an HVC
>> or an SMC command has to be issued.
>>
>> The current implementation always uses SMC. This results in crashes on
>> systems where the PSCI firmware is implemented in the hypervisor, e.g.
>> qemu-arm64_defconfig.
>>
>> The logic to decide which call is needed based on the device tree is
>> already implemented in the PSCI firmware driver. During the EFI runtime
>> the device driver model is not available. But we can minimize code
>> duplication by merging the EFI runtime reset and poweroff code with
>> the PSCI firmware driver.
>>
>> As the same HVC/SMC problem is also evident for the ARMv8 do_poweroff
>> and reset_misc routines let's move them into the same code module.
>>
>> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
>> Reviewed-by: Sumit Garg <sumit.garg at linaro.org>
>> Tested-by: Sumit Garg <sumit.garg at linaro.org>
>> ---
>> Travis reporteded no errors in
>> https://travis-ci.org/xypron2/u-boot/builds/442613876
>>
>> v4:
>> 	fix reset_misc() too
>> 	avoid switch statement
>> v3:
>> 	update commit message
>> v2:
>> 	Use PSCI firmware driver to detect call method.
>> 	Thanks to Sumit for pointing me at dtb parsing as part of
>> 	"psci_probe()
>> ---
>>  arch/arm/cpu/armv7/smccc-call.S |   2 +
>>  arch/arm/cpu/armv8/Kconfig      |   1 +
>>  arch/arm/cpu/armv8/fwcall.c     |  52 ++---------------
>>  arch/arm/cpu/armv8/smccc-call.S |   2 +
>>  drivers/firmware/psci.c         | 100 +++++++++++++++++++++++++++-----
>>  include/linux/psci.h            |   6 +-
>>  6 files changed, 96 insertions(+), 67 deletions(-)
>>
>> diff --git a/arch/arm/cpu/armv7/smccc-call.S b/arch/arm/cpu/armv7/smccc-call.S
>> index 0d8b59eb6b..eae69e36c3 100644
>> --- a/arch/arm/cpu/armv7/smccc-call.S
>> +++ b/arch/arm/cpu/armv7/smccc-call.S
>> @@ -7,6 +7,8 @@
>>  #include <asm/opcodes-sec.h>
>>  #include <asm/opcodes-virt.h>
>>  
>> +	.section	.text.efi_runtime
>> +
>>  #define UNWIND(x...)
>>  	/*
>>  	 * Wrap c macros in asm macros to delay expansion until after the
>> diff --git a/arch/arm/cpu/armv8/Kconfig b/arch/arm/cpu/armv8/Kconfig
>> index c8bebabdf6..d643981b73 100644
>> --- a/arch/arm/cpu/armv8/Kconfig
>> +++ b/arch/arm/cpu/armv8/Kconfig
>> @@ -96,6 +96,7 @@ endmenu
>>  config PSCI_RESET
>>  	bool "Use PSCI for reset and shutdown"
>>  	default y
>> +	select ARM_SMCCC if OF_CONTROL
>>  	depends on !ARCH_EXYNOS7 && !ARCH_BCM283X && \
>>  		   !TARGET_LS2080A_SIMU && !TARGET_LS2080AQDS && \
>>  		   !TARGET_LS2080ARDB && !TARGET_LS2080A_EMU && \
>> diff --git a/arch/arm/cpu/armv8/fwcall.c b/arch/arm/cpu/armv8/fwcall.c
>> index 0ba3dad8cc..9957c2974b 100644
>> --- a/arch/arm/cpu/armv8/fwcall.c
>> +++ b/arch/arm/cpu/armv8/fwcall.c
>> @@ -7,7 +7,6 @@
>>  
>>  #include <asm-offsets.h>
>>  #include <config.h>
>> -#include <efi_loader.h>
>>  #include <version.h>
>>  #include <asm/macro.h>
>>  #include <asm/psci.h>
>> @@ -19,7 +18,7 @@
>>   * x0~x7: input arguments
>>   * x0~x3: output arguments
>>   */
>> -static void __efi_runtime hvc_call(struct pt_regs *args)
>> +static void hvc_call(struct pt_regs *args)
>>  {
>>  	asm volatile(
>>  		"ldr x0, %0\n"
>> @@ -53,7 +52,7 @@ static void __efi_runtime hvc_call(struct pt_regs *args)
>>   * x0~x3: output arguments
>>   */
>>  
>> -void __efi_runtime smc_call(struct pt_regs *args)
>> +void smc_call(struct pt_regs *args)
>>  {
>>  	asm volatile(
>>  		"ldr x0, %0\n"
>> @@ -83,9 +82,9 @@ void __efi_runtime smc_call(struct pt_regs *args)
>>   * use PSCI on U-Boot running below a hypervisor, please detect
>>   * this and set the flag accordingly.
>>   */
>> -static const __efi_runtime_data bool use_smc_for_psci = true;
>> +static const bool use_smc_for_psci = true;
>>  
>> -void __noreturn __efi_runtime psci_system_reset(void)
>> +void __noreturn psci_system_reset(void)
>>  {
>>  	struct pt_regs regs;
>>  
>> @@ -100,7 +99,7 @@ void __noreturn __efi_runtime psci_system_reset(void)
>>  		;
>>  }
>>  
>> -void __noreturn __efi_runtime psci_system_off(void)
>> +void __noreturn psci_system_off(void)
>>  {
>>  	struct pt_regs regs;
>>  
>> @@ -114,44 +113,3 @@ void __noreturn __efi_runtime psci_system_off(void)
>>  	while (1)
>>  		;
>>  }
>> -
>> -#ifdef CONFIG_CMD_POWEROFF
>> -int do_poweroff(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
>> -{
>> -	puts("poweroff ...\n");
>> -
>> -	udelay(50000); /* wait 50 ms */
>> -
>> -	disable_interrupts();
>> -
>> -	psci_system_off();
>> -
>> -	/*NOTREACHED*/
>> -	return 0;
>> -}
>> -#endif
>> -
>> -#ifdef CONFIG_PSCI_RESET
>> -void reset_misc(void)
>> -{
>> -	psci_system_reset();
>> -}
>> -
>> -#ifdef CONFIG_EFI_LOADER
>> -void __efi_runtime EFIAPI efi_reset_system(
>> -			enum efi_reset_type reset_type,
>> -			efi_status_t reset_status,
>> -			unsigned long data_size, void *reset_data)
>> -{
>> -	if (reset_type == EFI_RESET_COLD ||
>> -	    reset_type == EFI_RESET_WARM ||
>> -	    reset_type == EFI_RESET_PLATFORM_SPECIFIC) {
>> -		psci_system_reset();
>> -	} else if (reset_type == EFI_RESET_SHUTDOWN) {
>> -		psci_system_off();
>> -	}
>> -
>> -	while (1) { }
>> -}
>> -#endif /* CONFIG_EFI_LOADER */
>> -#endif /* CONFIG_PSCI_RESET */
>> diff --git a/arch/arm/cpu/armv8/smccc-call.S b/arch/arm/cpu/armv8/smccc-call.S
>> index 16c9e298b4..86de4b4089 100644
>> --- a/arch/arm/cpu/armv8/smccc-call.S
>> +++ b/arch/arm/cpu/armv8/smccc-call.S
>> @@ -6,6 +6,8 @@
>>  #include <linux/arm-smccc.h>
>>  #include <generated/asm-offsets.h>
>>  
>> +	.section	.text.efi_runtime
>> +
>>  	.macro SMCCC instr
>>  	.cfi_startproc
>>  	\instr	#0
>> diff --git a/drivers/firmware/psci.c b/drivers/firmware/psci.c
>> index 2cb35f356f..7ec5eb094b 100644
>> --- a/drivers/firmware/psci.c
>> +++ b/drivers/firmware/psci.c
>> @@ -9,31 +9,38 @@
>>  #include <common.h>
>>  #include <dm.h>
>>  #include <dm/lists.h>
>> +#include <efi_loader.h>
>>  #include <linux/libfdt.h>
>>  #include <linux/arm-smccc.h>
>>  #include <linux/errno.h>
>>  #include <linux/printk.h>
>>  #include <linux/psci.h>
>>  
>> -psci_fn *invoke_psci_fn;
>> +#define DRIVER_NAME "psci"
>>  
>> -static unsigned long __invoke_psci_fn_hvc(unsigned long function_id,
>> -			unsigned long arg0, unsigned long arg1,
>> -			unsigned long arg2)
>> -{
>> -	struct arm_smccc_res res;
>> +#define PSCI_METHOD_HVC 1
>> +#define PSCI_METHOD_SMC 2
>>  
>> -	arm_smccc_hvc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
>> -	return res.a0;
>> -}
>> +int __efi_runtime_data psci_method;
>>  
>> -static unsigned long __invoke_psci_fn_smc(unsigned long function_id,
>> -			unsigned long arg0, unsigned long arg1,
>> -			unsigned long arg2)
>> +unsigned long __efi_runtime invoke_psci_fn
>> +		(unsigned long function_id, unsigned long arg0,
>> +		 unsigned long arg1, unsigned long arg2)
>>  {
>>  	struct arm_smccc_res res;
>>  
>> -	arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
>> +	/*
>> +	 * In the __efi_runtime we need to avoid the switch statement. In some
>> +	 * cases the compiler creates lookup tables to implement switch. These
>> +	 * tables are not correctly relocated when SetVirtualAddressMap is
>> +	 * called.
>> +	 */
>> +	if (psci_method == PSCI_METHOD_SMC)
>> +		arm_smccc_smc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
>> +	else if (psci_method == PSCI_METHOD_HVC)
>> +		arm_smccc_hvc(function_id, arg0, arg1, arg2, 0, 0, 0, 0, &res);
>> +	else
>> +		res.a0 = PSCI_RET_DISABLED;
>>  	return res.a0;
>>  }
>>  
>> @@ -67,9 +74,9 @@ static int psci_probe(struct udevice *dev)
>>  	}
>>  
>>  	if (!strcmp("hvc", method)) {
>> -		invoke_psci_fn = __invoke_psci_fn_hvc;
>> +		psci_method = PSCI_METHOD_HVC;
>>  	} else if (!strcmp("smc", method)) {
>> -		invoke_psci_fn = __invoke_psci_fn_smc;
>> +		psci_method = PSCI_METHOD_SMC;
>>  	} else {
>>  		pr_warn("invalid \"method\" property: %s\n", method);
>>  		return -EINVAL;
>> @@ -78,6 +85,67 @@ static int psci_probe(struct udevice *dev)
>>  	return 0;
>>  }
>>  
>> +/**
>> + * void do_psci_probe() - probe PSCI firmware driver
>> + *
>> + * Ensure that psci_method is initialized.
>> + */
>> +static void __maybe_unused do_psci_probe(void)
>> +{
>> +	struct udevice *dev;
>> +
>> +	uclass_get_device_by_name(UCLASS_FIRMWARE, DRIVER_NAME, &dev);
>> +}
>> +
>> +#ifdef CONFIG_EFI_LOADER
> 
> I think this should be #if IS_ENABLED(CONFIG_EFI_LOADER) &&
> IS_ENABLED(CONFIG_PSCI_RESET), as otherwise we may trigger unexpected
> PSCI resets from efi land that wouldn't happen with normal cmds.
> 
> 
> Alex

U-Boot is the little servant that helps the rider on the horse and
neither horse nor rider.

Hence U-Boot should not unnecessarily interfere with the communication
between the operating system and the PSCI firmware.

I cannot imagine any use case where the authorized user in the operating
system executes a reboot or shutdown command and expects the system
simply not to do it.

Best regards

Heinrich


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