Re: [Xen-devel] [PATCH v3 02/17] xen/arm: vsmc: Implement SMCCC 1.1

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Thu, 15 Feb 2018, Julien Grall wrote:
> The new SMC Calling Convention (v1.1) allows for a reduced overhead when
> calling into the firmware, and provides a new feature discovery
> mechanism. See "Firmware interfaces for mitigating CVE-2017-5715"
> ARM DEN 00070A.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>     Changes in v3:
>         - Use ARM_SMCCC_NOT_SUPPORTED rather than hardcoded return
> 
>     Changes in v2:
>         - Add a humand readable name for the specification
> ---
>  xen/arch/arm/vpsci.c        |  1 +
>  xen/arch/arm/vsmc.c         | 23 +++++++++++++++++++++++
>  xen/include/asm-arm/smccc.h | 18 +++++++++++++++++-
>  3 files changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/xen/arch/arm/vpsci.c b/xen/arch/arm/vpsci.c
> index e82b62db1a..19ee7caeb4 100644
> --- a/xen/arch/arm/vpsci.c
> +++ b/xen/arch/arm/vpsci.c
> @@ -212,6 +212,7 @@ static int32_t do_psci_1_0_features(uint32_t psci_func_id)
>      case PSCI_0_2_FN32_SYSTEM_OFF:
>      case PSCI_0_2_FN32_SYSTEM_RESET:
>      case PSCI_1_0_FN32_PSCI_FEATURES:
> +    case ARM_SMCCC_VERSION_FID:
>          return 0;
>      default:
>          return PSCI_NOT_SUPPORTED;
> diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
> index 3d3bd95fee..7ec492741b 100644
> --- a/xen/arch/arm/vsmc.c
> +++ b/xen/arch/arm/vsmc.c
> @@ -81,6 +81,26 @@ static bool fill_function_call_count(struct cpu_user_regs 
> *regs, uint32_t cnt)
>      return true;
>  }
>  
> +/* SMCCC interface for ARM Architecture */
> +static bool handle_arch(struct cpu_user_regs *regs)
> +{
> +    uint32_t fid = (uint32_t)get_user_reg(regs, 0);
> +
> +    switch ( fid )
> +    {
> +    case ARM_SMCCC_VERSION_FID:
> +        set_user_reg(regs, 0, ARM_SMCCC_VERSION_1_1);
> +        return true;
> +
> +    case ARM_SMCCC_ARCH_FEATURES_FID:
> +        /* Nothing supported yet */
> +        set_user_reg(regs, 0, ARM_SMCCC_NOT_SUPPORTED);
> +        return true;
> +    }
> +
> +    return false;
> +}
> +
>  /* SMCCC interface for hypervisor. Tell about itself. */
>  static bool handle_hypervisor(struct cpu_user_regs *regs)
>  {
> @@ -188,6 +208,9 @@ static bool vsmccc_handle_call(struct cpu_user_regs *regs)
>      {
>          switch ( smccc_get_owner(funcid) )
>          {
> +        case ARM_SMCCC_OWNER_ARCH:
> +            handled = handle_arch(regs);
> +            break;
>          case ARM_SMCCC_OWNER_HYPERVISOR:
>              handled = handle_hypervisor(regs);
>              break;
> diff --git a/xen/include/asm-arm/smccc.h b/xen/include/asm-arm/smccc.h
> index 62b3a8cdf5..629cc5150b 100644
> --- a/xen/include/asm-arm/smccc.h
> +++ b/xen/include/asm-arm/smccc.h
> @@ -16,6 +16,9 @@
>  #ifndef __ASM_ARM_SMCCC_H__
>  #define __ASM_ARM_SMCCC_H__
>  
> +#define ARM_SMCCC_VERSION_1_0   0x10000
> +#define ARM_SMCCC_VERSION_1_1   0x10001
> +
>  /*
>   * This file provides common defines for ARM SMC Calling Convention as
>   * specified in
> @@ -100,8 +103,21 @@ static inline uint32_t smccc_get_owner(register_t funcid)
>                         ARM_SMCCC_OWNER_##owner,     \
>                         0xFF03)
>  
> -/* Only one error code defined in SMCCC */
> +#define ARM_SMCCC_VERSION_FID                       \
> +    ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,         \
> +                       ARM_SMCCC_CONV_32,           \
> +                       ARM_SMCCC_OWNER_ARCH,        \
> +                       0x0)                         \
> +
> +#define ARM_SMCCC_ARCH_FEATURES_FID                 \
> +    ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,         \
> +                       ARM_SMCCC_CONV_32,           \
> +                       ARM_SMCCC_OWNER_ARCH,        \
> +                       0x1)
> +
> +/* SMCCC error codes */
>  #define ARM_SMCCC_ERR_UNKNOWN_FUNCTION  (-1)
> +#define ARM_SMCCC_NOT_SUPPORTED         (-1)
>  
>  /* SMCCC function identifier range which is reserved for existing APIs */
>  #define ARM_SMCCC_RESERVED_RANGE_START  0x0
> -- 
> 2.11.0
> 

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