Re: [XEN PATCH v10 04/24] xen/arm: tee: add a primitive FF-A mediator

[Bertrand Marquis <Bertrand.Marquis@xxxxxxx>]

Hi Jens,

> On 17 Jul 2023, at 09:20, Jens Wiklander <jens.wiklander@xxxxxxxxxx> wrote:
> 
> Adds a FF-A version 1.1 [1] mediator to communicate with a Secure
> Partition in secure world.
> 
> This commit brings in only the parts needed to negotiate FF-A version
> number with guest and SPMC.
> 
> [1] https://developer.arm.com/documentation/den0077/e
> Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
> ---
> xen/arch/arm/include/asm/psci.h    |   4 +
> xen/arch/arm/include/asm/tee/ffa.h |  35 +++++
> xen/arch/arm/tee/Kconfig           |  11 ++
> xen/arch/arm/tee/Makefile          |   1 +
> xen/arch/arm/tee/ffa.c             | 225 +++++++++++++++++++++++++++++
> xen/arch/arm/vsmc.c                |  17 ++-
> xen/include/public/arch-arm.h      |   1 +
> 7 files changed, 291 insertions(+), 3 deletions(-)
> create mode 100644 xen/arch/arm/include/asm/tee/ffa.h
> create mode 100644 xen/arch/arm/tee/ffa.c
> 
> diff --git a/xen/arch/arm/include/asm/psci.h b/xen/arch/arm/include/asm/psci.h
> index 832f77afff3a..4780972621bb 100644
> --- a/xen/arch/arm/include/asm/psci.h
> +++ b/xen/arch/arm/include/asm/psci.h
> @@ -24,6 +24,10 @@ void call_psci_cpu_off(void);
> void call_psci_system_off(void);
> void call_psci_system_reset(void);
> 
> +/* Range of allocated PSCI function numbers */
> +#define PSCI_FNUM_MIN_VALUE                 _AC(0,U)
> +#define PSCI_FNUM_MAX_VALUE                 _AC(0x1f,U)
> +
> /* PSCI v0.2 interface */
> #define PSCI_0_2_FN32(nr) ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,             
> \
>                                              ARM_SMCCC_CONV_32,               
> \
> diff --git a/xen/arch/arm/include/asm/tee/ffa.h 
> b/xen/arch/arm/include/asm/tee/ffa.h
> new file mode 100644
> index 000000000000..44361a4e78e4
> --- /dev/null
> +++ b/xen/arch/arm/include/asm/tee/ffa.h
> @@ -0,0 +1,35 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * xen/arch/arm/include/asm/tee/ffa.h
> + *
> + * Arm Firmware Framework for ARMv8-A(FFA) mediator
> + *
> + * Copyright (C) 2023  Linaro Limited
> + */
> +
> +#ifndef __ASM_ARM_TEE_FFA_H__
> +#define __ASM_ARM_TEE_FFA_H__
> +
> +#include <xen/const.h>
> +#include <xen/kconfig.h>
> +
> +#include <asm/smccc.h>
> +#include <asm/types.h>
> +
> +#define FFA_FNUM_MIN_VALUE              _AC(0x60,U)
> +#define FFA_FNUM_MAX_VALUE              _AC(0x86,U)
> +
> +static inline bool is_ffa_fid(uint32_t fid)
> +{
> +    uint32_t fn = fid & ARM_SMCCC_FUNC_MASK;
> +
> +    return fn >= FFA_FNUM_MIN_VALUE && fn <= FFA_FNUM_MAX_VALUE;
> +}
> +
> +#ifdef CONFIG_FFA
> +#define FFA_NR_FUNCS    12
> +#else
> +#define FFA_NR_FUNCS    0
> +#endif
> +
> +#endif /*__ASM_ARM_TEE_FFA_H__*/
> diff --git a/xen/arch/arm/tee/Kconfig b/xen/arch/arm/tee/Kconfig
> index 392169b2559d..923f08ba8cb7 100644
> --- a/xen/arch/arm/tee/Kconfig
> +++ b/xen/arch/arm/tee/Kconfig
> @@ -8,3 +8,14 @@ config OPTEE
>  virtualization-enabled OP-TEE present. You can learn more
>  about virtualization for OP-TEE at
>  https://optee.readthedocs.io/architecture/virtualization.html
> +
> +config FFA
> + bool "Enable FF-A mediator support (UNSUPPORTED)" if UNSUPPORTED
> + default n
> + depends on ARM_64

Even if the tee Makefile is only included if CONFIG_TEE is activated,
the missing dependency on TEE here allows to select FFA without TEE
resulting in a config with FFA activated but not compiled in.

No build error is coming from this, FFA is just not in if selected without TEE.

Should be:

depends on ARM_64 && TEE

I am ok if this is fixed on commit and my R-B kept.

Cheers
Bertrand

> + help
> +  This option enables a minimal FF-A mediator. The mediator is
> +  generic as it follows the FF-A specification [1], but it only
> +  implements a small subset of the specification.
> +
> +  [1] https://developer.arm.com/documentation/den0077/latest
> diff --git a/xen/arch/arm/tee/Makefile b/xen/arch/arm/tee/Makefile
> index 982c87968447..58a1015e40e0 100644
> --- a/xen/arch/arm/tee/Makefile
> +++ b/xen/arch/arm/tee/Makefile
> @@ -1,2 +1,3 @@
> +obj-$(CONFIG_FFA) += ffa.o
> obj-y += tee.o
> obj-$(CONFIG_OPTEE) += optee.o
> diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
> new file mode 100644
> index 000000000000..927c4d33a380
> --- /dev/null
> +++ b/xen/arch/arm/tee/ffa.c
> @@ -0,0 +1,225 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * xen/arch/arm/tee/ffa.c
> + *
> + * Arm Firmware Framework for ARMv8-A (FF-A) mediator
> + *
> + * Copyright (C) 2023  Linaro Limited
> + */
> +
> +#include <xen/bitops.h>
> +#include <xen/domain_page.h>
> +#include <xen/errno.h>
> +#include <xen/init.h>
> +#include <xen/lib.h>
> +#include <xen/sched.h>
> +#include <xen/sizes.h>
> +#include <xen/types.h>
> +
> +#include <asm/event.h>
> +#include <asm/regs.h>
> +#include <asm/smccc.h>
> +#include <asm/tee/ffa.h>
> +#include <asm/tee/tee.h>
> +
> +/* Error codes */
> +#define FFA_RET_OK                      0
> +#define FFA_RET_NOT_SUPPORTED           -1
> +#define FFA_RET_INVALID_PARAMETERS      -2
> +#define FFA_RET_NO_MEMORY               -3
> +#define FFA_RET_BUSY                    -4
> +#define FFA_RET_INTERRUPTED             -5
> +#define FFA_RET_DENIED                  -6
> +#define FFA_RET_RETRY                   -7
> +#define FFA_RET_ABORTED                 -8
> +
> +/* FFA_VERSION helpers */
> +#define FFA_VERSION_MAJOR_SHIFT         16U
> +#define FFA_VERSION_MAJOR_MASK          0x7FFFU
> +#define FFA_VERSION_MINOR_SHIFT         0U
> +#define FFA_VERSION_MINOR_MASK          0xFFFFU
> +#define MAKE_FFA_VERSION(major, minor)  \
> +        ((((major) & FFA_VERSION_MAJOR_MASK) << FFA_VERSION_MAJOR_SHIFT) | \
> +         ((minor) & FFA_VERSION_MINOR_MASK))
> +
> +#define FFA_VERSION_1_0         MAKE_FFA_VERSION(1, 0)
> +#define FFA_VERSION_1_1         MAKE_FFA_VERSION(1, 1)
> +/* The minimal FF-A version of the SPMC that can be supported */
> +#define FFA_MIN_SPMC_VERSION    FFA_VERSION_1_1
> +
> +/*
> + * This is the version we want to use in communication with guests and SPs.
> + * During negotiation with a guest or a SP we may need to lower it for
> + * that particular guest or SP.
> + */
> +#define FFA_MY_VERSION_MAJOR    1U
> +#define FFA_MY_VERSION_MINOR    1U
> +#define FFA_MY_VERSION          MAKE_FFA_VERSION(FFA_MY_VERSION_MAJOR, \
> +                                                 FFA_MY_VERSION_MINOR)
> +
> +/* Function IDs */
> +#define FFA_ERROR                       0x84000060U
> +#define FFA_SUCCESS_32                  0x84000061U
> +#define FFA_VERSION                     0x84000063U
> +
> +struct ffa_ctx {
> +    /* FF-A version used by the guest */
> +    uint32_t guest_vers;
> +};
> +
> +/* Negotiated FF-A version to use with the SPMC */
> +static uint32_t __ro_after_init ffa_version;
> +
> +static bool ffa_get_version(uint32_t *vers)
> +{
> +    const struct arm_smccc_1_2_regs arg = {
> +        .a0 = FFA_VERSION,
> +        .a1 = FFA_MY_VERSION,
> +    };
> +    struct arm_smccc_1_2_regs resp;
> +
> +    arm_smccc_1_2_smc(&arg, &resp);
> +    if ( resp.a0 == FFA_RET_NOT_SUPPORTED )
> +    {
> +        gprintk(XENLOG_ERR, "ffa: FFA_VERSION returned not supported\n");
> +        return false;
> +    }
> +
> +    *vers = resp.a0;
> +
> +    return true;
> +}
> +
> +static void set_regs(struct cpu_user_regs *regs, register_t v0, register_t 
> v1,
> +                     register_t v2, register_t v3, register_t v4, register_t 
> v5,
> +                     register_t v6, register_t v7)
> +{
> +        set_user_reg(regs, 0, v0);
> +        set_user_reg(regs, 1, v1);
> +        set_user_reg(regs, 2, v2);
> +        set_user_reg(regs, 3, v3);
> +        set_user_reg(regs, 4, v4);
> +        set_user_reg(regs, 5, v5);
> +        set_user_reg(regs, 6, v6);
> +        set_user_reg(regs, 7, v7);
> +}
> +
> +static void handle_version(struct cpu_user_regs *regs)
> +{
> +    struct domain *d = current->domain;
> +    struct ffa_ctx *ctx = d->arch.tee;
> +    uint32_t vers = get_user_reg(regs, 1);
> +
> +    if ( vers < FFA_VERSION_1_1 )
> +        vers = FFA_VERSION_1_0;
> +    else
> +        vers = FFA_VERSION_1_1;
> +
> +    ctx->guest_vers = vers;
> +    set_regs(regs, vers, 0, 0, 0, 0, 0, 0, 0);
> +}
> +
> +static bool ffa_handle_call(struct cpu_user_regs *regs)
> +{
> +    uint32_t fid = get_user_reg(regs, 0);
> +    struct domain *d = current->domain;
> +    struct ffa_ctx *ctx = d->arch.tee;
> +
> +    if ( !ctx )
> +        return false;
> +
> +    switch ( fid )
> +    {
> +    case FFA_VERSION:
> +        handle_version(regs);
> +        return true;
> +
> +    default:
> +        gprintk(XENLOG_ERR, "ffa: unhandled fid 0x%x\n", fid);
> +        return false;
> +    }
> +}
> +
> +static int ffa_domain_init(struct domain *d)
> +{
> +    struct ffa_ctx *ctx;
> +
> +    if ( !ffa_version )
> +        return -ENODEV;
> +
> +    ctx = xzalloc(struct ffa_ctx);
> +    if ( !ctx )
> +        return -ENOMEM;
> +
> +    d->arch.tee = ctx;
> +
> +    return 0;
> +}
> +
> +/* This function is supposed to undo what ffa_domain_init() has done */
> +static int ffa_domain_teardown(struct domain *d)
> +{
> +    struct ffa_ctx *ctx = d->arch.tee;
> +
> +    if ( !ctx )
> +        return 0;
> +
> +    XFREE(d->arch.tee);
> +
> +    return 0;
> +}
> +
> +static int ffa_relinquish_resources(struct domain *d)
> +{
> +    return 0;
> +}
> +
> +static bool ffa_probe(void)
> +{
> +    uint32_t vers;
> +    unsigned int major_vers;
> +    unsigned int minor_vers;
> +
> +    /*
> +     * psci_init_smccc() updates this value with what's reported by EL-3
> +     * or secure world.
> +     */
> +    if ( smccc_ver < ARM_SMCCC_VERSION_1_2 )
> +    {
> +        printk(XENLOG_ERR
> +               "ffa: unsupported SMCCC version %#x (need at least %#x)\n",
> +               smccc_ver, ARM_SMCCC_VERSION_1_2);
> +        return false;
> +    }
> +
> +    if ( !ffa_get_version(&vers) )
> +        return false;
> +
> +    if ( vers < FFA_MIN_SPMC_VERSION || vers > FFA_MY_VERSION )
> +    {
> +        printk(XENLOG_ERR "ffa: Incompatible version %#x found\n", vers);
> +        return false;
> +    }
> +
> +    major_vers = (vers >> FFA_VERSION_MAJOR_SHIFT) & FFA_VERSION_MAJOR_MASK;
> +    minor_vers = vers & FFA_VERSION_MINOR_MASK;
> +    printk(XENLOG_INFO "ARM FF-A Mediator version %u.%u\n",
> +           FFA_MY_VERSION_MAJOR, FFA_MY_VERSION_MINOR);
> +    printk(XENLOG_INFO "ARM FF-A Firmware version %u.%u\n",
> +           major_vers, minor_vers);
> +
> +    ffa_version = vers;
> +
> +    return true;
> +}
> +
> +static const struct tee_mediator_ops ffa_ops =
> +{
> +    .probe = ffa_probe,
> +    .domain_init = ffa_domain_init,
> +    .domain_teardown = ffa_domain_teardown,
> +    .relinquish_resources = ffa_relinquish_resources,
> +    .handle_call = ffa_handle_call,
> +};
> +
> +REGISTER_TEE_MEDIATOR(ffa, "FF-A", XEN_DOMCTL_CONFIG_TEE_FFA, &ffa_ops);
> diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
> index cd68fa80e98a..7f2f5eb9ce3d 100644
> --- a/xen/arch/arm/vsmc.c
> +++ b/xen/arch/arm/vsmc.c
> @@ -15,6 +15,7 @@
> #include <asm/monitor.h>
> #include <asm/regs.h>
> #include <asm/smccc.h>
> +#include <asm/tee/ffa.h>
> #include <asm/tee/tee.h>
> #include <asm/traps.h>
> #include <asm/vpsci.h>
> @@ -24,7 +25,7 @@
> #define XEN_SMCCC_FUNCTION_COUNT 3
> 
> /* Number of functions currently supported by Standard Service Service Calls. 
> */
> -#define SSSC_SMCCC_FUNCTION_COUNT (3 + VPSCI_NR_FUNCS)
> +#define SSSC_SMCCC_FUNCTION_COUNT (3 + VPSCI_NR_FUNCS + FFA_NR_FUNCS)
> 
> static bool fill_uid(struct cpu_user_regs *regs, xen_uuid_t uuid)
> {
> @@ -188,13 +189,23 @@ static bool handle_existing_apis(struct cpu_user_regs 
> *regs)
>     return do_vpsci_0_1_call(regs, fid);
> }
> 
> +static bool is_psci_fid(uint32_t fid)
> +{
> +    uint32_t fn = fid & ARM_SMCCC_FUNC_MASK;
> +
> +    return fn >= PSCI_FNUM_MIN_VALUE && fn <= PSCI_FNUM_MAX_VALUE;
> +}
> +
> /* PSCI 0.2 interface and other Standard Secure Calls */
> static bool handle_sssc(struct cpu_user_regs *regs)
> {
>     uint32_t fid = (uint32_t)get_user_reg(regs, 0);
> 
> -    if ( do_vpsci_0_2_call(regs, fid) )
> -        return true;
> +    if ( is_psci_fid(fid) )
> +        return do_vpsci_0_2_call(regs, fid);
> +
> +    if ( is_ffa_fid(fid) )
> +        return tee_handle_call(regs);
> 
>     switch ( fid )
>     {
> diff --git a/xen/include/public/arch-arm.h b/xen/include/public/arch-arm.h
> index 38311f559581..c6449893e493 100644
> --- a/xen/include/public/arch-arm.h
> +++ b/xen/include/public/arch-arm.h
> @@ -296,6 +296,7 @@ DEFINE_XEN_GUEST_HANDLE(vcpu_guest_context_t);
> 
> #define XEN_DOMCTL_CONFIG_TEE_NONE      0
> #define XEN_DOMCTL_CONFIG_TEE_OPTEE     1
> +#define XEN_DOMCTL_CONFIG_TEE_FFA       2
> 
> struct xen_arch_domainconfig {
>     /* IN/OUT */
> -- 
> 2.34.1
>