Re: [PATCH v6 06/43] hw/cxl/device: Implement basic mailbox (8.2.8.4)

["Alex Bennée" <alex.bennee@linaro.org>]

Jonathan Cameron <Jonathan.Cameron@huawei.com> writes:

> From: Ben Widawsky <ben.widawsky@intel.com>
>
> This is the beginning of implementing mailbox support for CXL 2.0
> devices. The implementation recognizes when the doorbell is rung,
> handles the command/payload, clears the doorbell while returning error
> codes and data.
>
> Generally the mailbox mechanism is designed to permit communication
> between the host OS and the firmware running on the device. For our
> purposes, we emulate both the firmware, implemented primarily in
> cxl-mailbox-utils.c, and the hardware.
>
> No commands are implemented yet.
>
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
>  hw/cxl/cxl-device-utils.c   | 128 ++++++++++++++++++++++++++-
>  hw/cxl/cxl-mailbox-utils.c  | 171 ++++++++++++++++++++++++++++++++++++
>  hw/cxl/meson.build          |   1 +
>  include/hw/cxl/cxl.h        |   3 +
>  include/hw/cxl/cxl_device.h |  19 +++-
>  5 files changed, 320 insertions(+), 2 deletions(-)
>
> diff --git a/hw/cxl/cxl-device-utils.c b/hw/cxl/cxl-device-utils.c
> index 0895b9d78b..39011468ef 100644
> --- a/hw/cxl/cxl-device-utils.c
> +++ b/hw/cxl/cxl-device-utils.c
> @@ -44,6 +44,114 @@ static uint64_t dev_reg_read(void *opaque, hwaddr offset, unsigned size)
>      return 0;
>  }
>  
> +static uint64_t mailbox_reg_read(void *opaque, hwaddr offset, unsigned size)
> +{
> +    CXLDeviceState *cxl_dstate = opaque;
> +
> +    switch (size) {
> +    case 1:
> +        return cxl_dstate->mbox_reg_state[offset];
> +    case 2:
> +        return cxl_dstate->mbox_reg_state16[offset / 2];
> +    case 4:
> +        return cxl_dstate->mbox_reg_state32[offset / 4];
> +    case 8:
> +        return cxl_dstate->mbox_reg_state64[offset / 8];
> +    default:
> +        g_assert_not_reached();
> +    }
> +}
> +
> +static void mailbox_mem_writel(uint32_t *reg_state, hwaddr offset,
> +                               uint64_t value)
> +{
> +    switch (offset) {
> +    case A_CXL_DEV_MAILBOX_CTRL:
> +        /* fallthrough */
> +    case A_CXL_DEV_MAILBOX_CAP:
> +        /* RO register */
> +        break;
> +    default:
> +        qemu_log_mask(LOG_UNIMP,
> +                      "%s Unexpected 32-bit access to 0x%" PRIx64 " (WI)\n",
> +                      __func__, offset);
> +        return;
> +    }
> +
> +    reg_state[offset / 4] = value;
> +}
> +
> +static void mailbox_mem_writeq(uint64_t *reg_state, hwaddr offset,
> +                               uint64_t value)
> +{
> +    switch (offset) {
> +    case A_CXL_DEV_MAILBOX_CMD:
> +        break;
> +    case A_CXL_DEV_BG_CMD_STS:
> +        /* BG not supported */
> +        /* fallthrough */
> +    case A_CXL_DEV_MAILBOX_STS:
> +        /* Read only register, will get updated by the state machine */
> +        return;
> +    default:
> +        qemu_log_mask(LOG_UNIMP,
> +                      "%s Unexpected 64-bit access to 0x%" PRIx64 " (WI)\n",
> +                      __func__, offset);
> +        return;
> +    }
> +
> +
> +    reg_state[offset / 8] = value;
> +}
> +
> +static void mailbox_reg_write(void *opaque, hwaddr offset, uint64_t value,
> +                              unsigned size)
> +{
> +    CXLDeviceState *cxl_dstate = opaque;
> +
> +    if (offset >= A_CXL_DEV_CMD_PAYLOAD) {
> +        memcpy(cxl_dstate->mbox_reg_state + offset, &value, size);
> +        return;
> +    }
> +
> +    /*
> +     * Lock is needed to prevent concurrent writes as well as to
> +     * prevent writes coming in while the firmware is processing.
> +     * Until background commands or the second mailbox are implemented
> +     * memory access is synchronized at a higher level (per memory region).
> +     */

What lock?

That said you probably don't need one as all access to IO space should
already be serialised by the BQL so even multiple vCPUs will serialise
their access.

> +
> +    switch (size) {
> +    case 4:
> +        mailbox_mem_writel(cxl_dstate->mbox_reg_state32, offset, value);
> +        break;
> +    case 8:
> +        mailbox_mem_writeq(cxl_dstate->mbox_reg_state64, offset, value);
> +        break;
> +    default:
> +        g_assert_not_reached();
> +    }
> +
> +    if (ARRAY_FIELD_EX32(cxl_dstate->mbox_reg_state32, CXL_DEV_MAILBOX_CTRL,
> +                         DOORBELL))
> +        cxl_process_mailbox(cxl_dstate);

You want some braces in there to meet coding standards.

> +}
> +
> +static const MemoryRegionOps mailbox_ops = {
> +    .read = mailbox_reg_read,
> +    .write = mailbox_reg_write,
> +    .endianness = DEVICE_LITTLE_ENDIAN,
> +    .valid = {
> +        .min_access_size = 1,
> +        .max_access_size = 8,
> +        .unaligned = false,
> +    },
> +    .impl = {
> +        .min_access_size = 1,
> +        .max_access_size = 8,
> +    },
> +};
> +
>  static const MemoryRegionOps dev_ops = {
>      .read = dev_reg_read,
>      .write = NULL, /* status register is read only */
> @@ -84,20 +192,33 @@ void cxl_device_register_block_init(Object *obj, CXLDeviceState *cxl_dstate)
>                            "cap-array", CXL_CAPS_SIZE);
>      memory_region_init_io(&cxl_dstate->device, obj, &dev_ops, cxl_dstate,
>                            "device-status", CXL_DEVICE_REGISTERS_LENGTH);
> +    memory_region_init_io(&cxl_dstate->mailbox, obj, &mailbox_ops, cxl_dstate,
> +                          "mailbox", CXL_MAILBOX_REGISTERS_LENGTH);
>  
>      memory_region_add_subregion(&cxl_dstate->device_registers, 0,
>                                  &cxl_dstate->caps);
>      memory_region_add_subregion(&cxl_dstate->device_registers,
>                                  CXL_DEVICE_REGISTERS_OFFSET,
>                                  &cxl_dstate->device);
> +    memory_region_add_subregion(&cxl_dstate->device_registers,
> +                                CXL_MAILBOX_REGISTERS_OFFSET,
> +                                &cxl_dstate->mailbox);
>  }
>  
>  static void device_reg_init_common(CXLDeviceState *cxl_dstate) { }
>  
> +static void mailbox_reg_init_common(CXLDeviceState *cxl_dstate)
> +{
> +    /* 2048 payload size, with no interrupt or background support */
> +    ARRAY_FIELD_DP32(cxl_dstate->mbox_reg_state32, CXL_DEV_MAILBOX_CAP,
> +                     PAYLOAD_SIZE, CXL_MAILBOX_PAYLOAD_SHIFT);
> +    cxl_dstate->payload_size = CXL_MAILBOX_MAX_PAYLOAD_SIZE;
> +}
> +
>  void cxl_device_register_init_common(CXLDeviceState *cxl_dstate)
>  {
>      uint64_t *cap_hdrs = cxl_dstate->caps_reg_state64;
> -    const int cap_count = 1;
> +    const int cap_count = 2;
>  
>      /* CXL Device Capabilities Array Register */
>      ARRAY_FIELD_DP64(cap_hdrs, CXL_DEV_CAP_ARRAY, CAP_ID, 0);
> @@ -106,4 +227,9 @@ void cxl_device_register_init_common(CXLDeviceState *cxl_dstate)
>  
>      cxl_device_cap_init(cxl_dstate, DEVICE, 1);
>      device_reg_init_common(cxl_dstate);
> +
> +    cxl_device_cap_init(cxl_dstate, MAILBOX, 2);
> +    mailbox_reg_init_common(cxl_dstate);
> +
> +    assert(cxl_initialize_mailbox(cxl_dstate) == 0);
>  }
> diff --git a/hw/cxl/cxl-mailbox-utils.c b/hw/cxl/cxl-mailbox-utils.c
> new file mode 100644
> index 0000000000..d497ec50a6
> --- /dev/null
> +++ b/hw/cxl/cxl-mailbox-utils.c
> @@ -0,0 +1,171 @@
> +/*
> + * CXL Utility library for mailbox interface
> + *
> + * Copyright(C) 2020 Intel Corporation.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2. See the
> + * COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "hw/cxl/cxl.h"
> +#include "hw/pci/pci.h"
> +#include "qemu/log.h"
> +#include "qemu/uuid.h"
> +
> +/*
> + * How to add a new command, example. The command set FOO, with cmd BAR.
> + *  1. Add the command set and cmd to the enum.
> + *     FOO    = 0x7f,
> + *          #define BAR 0
> + *  2. Implement the handler
> + *    static ret_code cmd_foo_bar(struct cxl_cmd *cmd,
> + *                                  CXLDeviceState *cxl_dstate, uint16_t *len)
> + *  3. Add the command to the cxl_cmd_set[][]
> + *    [FOO][BAR] = { "FOO_BAR", cmd_foo_bar, x, y },
> + *  4. Implement your handler
> + *     define_mailbox_handler(FOO_BAR) { ... return CXL_MBOX_SUCCESS; }
> + *
> + *
> + *  Writing the handler:
> + *    The handler will provide the &struct cxl_cmd, the &CXLDeviceState, and the
> + *    in/out length of the payload. The handler is responsible for consuming the
> + *    payload from cmd->payload and operating upon it as necessary. It must then
> + *    fill the output data into cmd->payload (overwriting what was there),
> + *    setting the length, and returning a valid return code.
> + *
> + *  XXX: The handler need not worry about endianess. The payload is read out of
> + *  a register interface that already deals with it.
> + */
> +
> +/* 8.2.8.4.5.1 Command Return Codes */
> +typedef enum {
> +    CXL_MBOX_SUCCESS = 0x0,
> +    CXL_MBOX_BG_STARTED = 0x1,
> +    CXL_MBOX_INVALID_INPUT = 0x2,
> +    CXL_MBOX_UNSUPPORTED = 0x3,
> +    CXL_MBOX_INTERNAL_ERROR = 0x4,
> +    CXL_MBOX_RETRY_REQUIRED = 0x5,
> +    CXL_MBOX_BUSY = 0x6,
> +    CXL_MBOX_MEDIA_DISABLED = 0x7,
> +    CXL_MBOX_FW_XFER_IN_PROGRESS = 0x8,
> +    CXL_MBOX_FW_XFER_OUT_OF_ORDER = 0x9,
> +    CXL_MBOX_FW_AUTH_FAILED = 0xa,
> +    CXL_MBOX_FW_INVALID_SLOT = 0xb,
> +    CXL_MBOX_FW_ROLLEDBACK = 0xc,
> +    CXL_MBOX_FW_REST_REQD = 0xd,
> +    CXL_MBOX_INVALID_HANDLE = 0xe,
> +    CXL_MBOX_INVALID_PA = 0xf,
> +    CXL_MBOX_INJECT_POISON_LIMIT = 0x10,
> +    CXL_MBOX_PERMANENT_MEDIA_FAILURE = 0x11,
> +    CXL_MBOX_ABORTED = 0x12,
> +    CXL_MBOX_INVALID_SECURITY_STATE = 0x13,
> +    CXL_MBOX_INCORRECT_PASSPHRASE = 0x14,
> +    CXL_MBOX_UNSUPPORTED_MAILBOX = 0x15,
> +    CXL_MBOX_INVALID_PAYLOAD_LENGTH = 0x16,
> +    CXL_MBOX_MAX = 0x17
> +} ret_code;
> +
> +struct cxl_cmd;
> +typedef ret_code (*opcode_handler)(struct cxl_cmd *cmd,
> +                                   CXLDeviceState *cxl_dstate, uint16_t *len);
> +struct cxl_cmd {
> +    const char *name;
> +    opcode_handler handler;
> +    ssize_t in;
> +    uint16_t effect; /* Reported in CEL */
> +    uint8_t *payload;
> +};
> +
> +#define DEFINE_MAILBOX_HANDLER_ZEROED(name, size)                         \
> +    uint16_t __zero##name = size;                                         \
> +    static ret_code cmd_##name(struct cxl_cmd *cmd,                       \
> +                               CXLDeviceState *cxl_dstate, uint16_t *len) \
> +    {                                                                     \
> +        *len = __zero##name;                                              \
> +        memset(cmd->payload, 0, *len);                                    \
> +        return CXL_MBOX_SUCCESS;                                          \
> +    }
> +#define DEFINE_MAILBOX_HANDLER_NOP(name)                                  \
> +    static ret_code cmd_##name(struct cxl_cmd *cmd,                       \
> +                               CXLDeviceState *cxl_dstate, uint16_t *len) \
> +    {                                                                     \
> +        return CXL_MBOX_SUCCESS;                                          \
> +    }
> +
> +static QemuUUID cel_uuid;
> +
> +static struct cxl_cmd cxl_cmd_set[256][256] = {};
> +
> +void cxl_process_mailbox(CXLDeviceState *cxl_dstate)
> +{
> +    uint16_t ret = CXL_MBOX_SUCCESS;
> +    struct cxl_cmd *cxl_cmd;
> +    uint64_t status_reg;
> +    opcode_handler h;
> +
> +    /*
> +     * current state of mailbox interface
> +     *  mbox_cap_reg = cxl_dstate->reg_state32[R_CXL_DEV_MAILBOX_CAP];
> +     *  mbox_ctrl_reg = cxl_dstate->reg_state32[R_CXL_DEV_MAILBOX_CTRL];
> +     *  status_reg = *(uint64_t *)&cxl_dstate->reg_state[A_CXL_DEV_MAILBOX_STS];
> +     */
> +    uint64_t command_reg = cxl_dstate->mbox_reg_state64[R_CXL_DEV_MAILBOX_CMD];
> +
> +    uint8_t set = FIELD_EX64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND_SET);
> +    uint8_t cmd = FIELD_EX64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND);
> +    uint16_t len = FIELD_EX64(command_reg, CXL_DEV_MAILBOX_CMD, LENGTH);
> +    cxl_cmd = &cxl_cmd_set[set][cmd];
> +    h = cxl_cmd->handler;
> +    if (!h) {
> +        qemu_log_mask(LOG_UNIMP, "Command %04xh not implemented\n",
> +                                 set << 8 | cmd);

is ret of CXL_MBOX_SUCCESS still ok for an unimplemented command?

> +        goto handled;
> +    }
> +
> +    if (len != cxl_cmd->in) {
> +        ret = CXL_MBOX_INVALID_PAYLOAD_LENGTH;
> +    }
> +
> +    cxl_cmd->payload = cxl_dstate->mbox_reg_state + A_CXL_DEV_CMD_PAYLOAD;
> +    ret = (*h)(cxl_cmd, cxl_dstate, &len);
> +    assert(len <= cxl_dstate->payload_size);
> +

Not super keen on the goto, it seems to me the you could trivially
re-arrange this to avoid it as it is not a super deep implementation.

if (h) {
  if (len == cxl_cmd->in) {
    /* do the thing */
  } else {
    ret = CXL_MBOX_INVALID_PAYLOAD_LENGTH;
} else {
  qemu_log_mask(LOG_UNIMP, "Command %04xh not implemented\n",
                set << 8 | cmd);
}
/* process the result */

> +handled:
> +    /* Set the return code */
> +    status_reg = FIELD_DP64(0, CXL_DEV_MAILBOX_STS, ERRNO, ret);
> +
> +    /* Set the return length */
> +    command_reg = FIELD_DP64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND_SET, 0);
> +    command_reg = FIELD_DP64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND, 0);
> +    command_reg = FIELD_DP64(command_reg, CXL_DEV_MAILBOX_CMD, LENGTH, len);
> +
> +    cxl_dstate->mbox_reg_state64[R_CXL_DEV_MAILBOX_CMD] = command_reg;
> +    cxl_dstate->mbox_reg_state64[R_CXL_DEV_MAILBOX_STS] = status_reg;
> +
> +    /* Tell the host we're done */
> +    ARRAY_FIELD_DP32(cxl_dstate->mbox_reg_state32, CXL_DEV_MAILBOX_CTRL,
> +                     DOORBELL, 0);
> +}
> +
> +int cxl_initialize_mailbox(CXLDeviceState *cxl_dstate)
> +{
> +    /* CXL 2.0: Table 169 Get Supported Logs Log Entry */
> +    const char *cel_uuidstr = "0da9c0b5-bf41-4b78-8f79-96b1623b3f17";
> +
> +    for (int set = 0; set < 256; set++) {
> +        for (int cmd = 0; cmd < 256; cmd++) {
> +            if (cxl_cmd_set[set][cmd].handler) {
> +                struct cxl_cmd *c = &cxl_cmd_set[set][cmd];
> +                struct cel_log *log =
> +                    &cxl_dstate->cel_log[cxl_dstate->cel_size];
> +
> +                log->opcode = (set << 8) | cmd;
> +                log->effect = c->effect;
> +                cxl_dstate->cel_size++;
> +            }
> +        }
> +    }
> +
> +    return qemu_uuid_parse(cel_uuidstr, &cel_uuid);
> +}
> diff --git a/hw/cxl/meson.build b/hw/cxl/meson.build
> index dd7c6f8e5a..e68eea2358 100644
> --- a/hw/cxl/meson.build
> +++ b/hw/cxl/meson.build
> @@ -2,4 +2,5 @@ softmmu_ss.add(when: 'CONFIG_CXL',
>                 if_true: files(
>                     'cxl-component-utils.c',
>                     'cxl-device-utils.c',
> +                   'cxl-mailbox-utils.c',
>                 ))
> diff --git a/include/hw/cxl/cxl.h b/include/hw/cxl/cxl.h
> index b9d1ac3fad..554ad93b6b 100644
> --- a/include/hw/cxl/cxl.h
> +++ b/include/hw/cxl/cxl.h
> @@ -14,4 +14,7 @@
>  #include "cxl_component.h"
>  #include "cxl_device.h"
>  
> +#define CXL_COMPONENT_REG_BAR_IDX 0
> +#define CXL_DEVICE_REG_BAR_IDX 2
> +
>  #endif
> diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> index 1ac0dcd97e..49dcca7e44 100644
> --- a/include/hw/cxl/cxl_device.h
> +++ b/include/hw/cxl/cxl_device.h
> @@ -95,7 +95,21 @@ typedef struct cxl_device_state {
>      };
>  
>      /* mmio for the mailbox registers 8.2.8.4 */
> -    MemoryRegion mailbox;
> +    struct {
> +        MemoryRegion mailbox;
> +        uint16_t payload_size;
> +        union {
> +            uint8_t mbox_reg_state[CXL_MAILBOX_REGISTERS_LENGTH];
> +            uint16_t mbox_reg_state16[CXL_MAILBOX_REGISTERS_LENGTH / 2];
> +            uint32_t mbox_reg_state32[CXL_MAILBOX_REGISTERS_LENGTH / 4];
> +            uint64_t mbox_reg_state64[CXL_MAILBOX_REGISTERS_LENGTH / 8];
> +        };
> +        struct cel_log {
> +            uint16_t opcode;
> +            uint16_t effect;
> +        } cel_log[1 << 16];
> +        size_t cel_size;
> +    };
>  
>      /* memory region for persistent memory, HDM */
>      uint64_t pmem_size;
> @@ -145,6 +159,9 @@ CXL_DEVICE_CAPABILITY_HEADER_REGISTER(DEVICE, CXL_DEVICE_CAP_HDR1_OFFSET)
>  CXL_DEVICE_CAPABILITY_HEADER_REGISTER(MAILBOX, CXL_DEVICE_CAP_HDR1_OFFSET + \
>                                                 CXL_DEVICE_CAP_REG_SIZE)
>  
> +int cxl_initialize_mailbox(CXLDeviceState *cxl_dstate);
> +void cxl_process_mailbox(CXLDeviceState *cxl_dstate);
> +
>  #define cxl_device_cap_init(dstate, reg, cap_id)                           \
>      do {                                                                   \
>          uint32_t *cap_hdrs = dstate->caps_reg_state32;                     \

Otherwise:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée