Re: [RFC PATCH v3 03/31] hw/cxl/device: Introduce a CXL device (8.2.8)

[Jonathan Cameron]

On Mon, 1 Feb 2021 16:59:20 -0800
Ben Widawsky <ben.widawsky@intel.com> wrote:

> A CXL device is a type of CXL component. Conceptually, a CXL device
> would be a leaf node in a CXL topology. From an emulation perspective,
> CXL devices are the most complex and so the actual implementation is
> reserved for discrete commits.
> 
> This new device type is specifically catered towards the eventual
> implementation of a Type3 CXL.mem device, 8.2.8.5 in the CXL 2.0
> specification.
> 
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
Really minor comments inline.

In the interests of avoiding giving myself a headache again
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  include/hw/cxl/cxl.h        |   1 +
>  include/hw/cxl/cxl_device.h | 155 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 156 insertions(+)
>  create mode 100644 include/hw/cxl/cxl_device.h
> 
> diff --git a/include/hw/cxl/cxl.h b/include/hw/cxl/cxl.h
> index 55f6cc30a5..23f52c4cf9 100644
> --- a/include/hw/cxl/cxl.h
> +++ b/include/hw/cxl/cxl.h
> @@ -12,6 +12,7 @@
>  
>  #include "cxl_pci.h"
>  #include "cxl_component.h"
> +#include "cxl_device.h"
>  
>  #endif
>  
> diff --git a/include/hw/cxl/cxl_device.h b/include/hw/cxl/cxl_device.h
> new file mode 100644
> index 0000000000..a85f250503
> --- /dev/null
> +++ b/include/hw/cxl/cxl_device.h
> @@ -0,0 +1,155 @@
> +/*
> + * QEMU CXL Devices
> + *
> + * Copyright (c) 2020 Intel
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2. See the
> + * COPYING file in the top-level directory.
> + */
> +
> +#ifndef CXL_DEVICE_H
> +#define CXL_DEVICE_H
> +
> +#include "hw/register.h"
> +
> +/*
> + * The following is how a CXL device's MMIO space is laid out. The only
> + * requirement from the spec is that the capabilities array and the 
> capability
> + * headers start at offset 0 and are contiguously packed. The headers 
> themselves
> + * provide offsets to the register fields. For this emulation, registers will
> + * start at offset 0x80 (m == 0x80). No secondary mailbox is implemented 
> which
> + * means that n = m + sizeof(mailbox registers) + sizeof(device registers).
> + *
> + * This is roughly described in 8.2.8 Figure 138 of the CXL 2.0 spec.
> + *
> + * n + PAYLOAD_SIZE_MAX  +---------------------------------+
> + *                       |                                 |
> + *                  ^    |                                 |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  |    |         Command Payload         |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  n    +---------------------------------+
> + *                  ^    |                                 |
> + *                  |    |    Device Capability Registers  |
> + *                  |    |    x, mailbox, y                |
> + *                  |    |                                 |
> + *                  m    +---------------------------------+
> + *                  ^    |     Device Capability Header y  |
> + *                  |    +---------------------------------+
> + *                  |    | Device Capability Header Mailbox|
> + *                  |    +------------- --------------------
> + *                  |    |     Device Capability Header x  |
> + *                  |    +---------------------------------+
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  |    |      Device Cap Array[0..n]     |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  |    |                                 |
> + *                  0    +---------------------------------+
> + */
> +
> +#define CXL_DEVICE_CAP_HDR1_OFFSET 0x10 /* Figure 138 */
> +#define CXL_DEVICE_CAP_REG_SIZE 0x10 /* 8.2.8.2 */
> +#define CXL_DEVICE_CAPS_MAX 4 /* 8.2.8.2.1 + 8.2.8.5 */
> +
> +#define CXL_DEVICE_REGISTERS_OFFSET 0x80 /* Read comment above */
> +#define CXL_DEVICE_REGISTERS_LENGTH 0x8 /* 8.2.8.3.1 */
> +
> +#define CXL_MAILBOX_REGISTERS_OFFSET \
> +    (CXL_DEVICE_REGISTERS_OFFSET + CXL_DEVICE_REGISTERS_LENGTH)
> +#define CXL_MAILBOX_REGISTERS_SIZE 0x20

Perhaps a ref to 8.2.8.4 or Figure 139 here somewhere?
Thanks for all the refs by the way. They make checking this a lot quicker!

> +#define CXL_MAILBOX_PAYLOAD_SHIFT 11
> +#define CXL_MAILBOX_MAX_PAYLOAD_SIZE (1 << CXL_MAILBOX_PAYLOAD_SHIFT)
> +#define CXL_MAILBOX_REGISTERS_LENGTH \
> +    (CXL_MAILBOX_REGISTERS_SIZE + CXL_MAILBOX_MAX_PAYLOAD_SIZE)
> +
> +typedef struct cxl_device_state {
> +    MemoryRegion device_registers;
> +
> +    /* mmio for device capabilities array - 8.2.8.2 */
> +    MemoryRegion caps;
> +
> +    /* mmio for the device status registers 8.2.8.3 */
> +    MemoryRegion device;
> +
> +    /* mmio for the mailbox registers 8.2.8.4 */
> +    MemoryRegion mailbox;
> +
> +    /* memory region for persistent memory, HDM */
> +    MemoryRegion *pmem;
> +
> +    /* memory region for volatile  memory, HDM */
> +    MemoryRegion *vmem;
> +} CXLDeviceState;
> +
> +/* Initialize the register block for a device */
> +void cxl_device_register_block_init(Object *obj, CXLDeviceState *dev);
> +
> +/* Set up default values for the register block */
> +void cxl_device_register_init_common(CXLDeviceState *dev);
> +
> +/* CXL 2.0 - 8.2.8.1 */
> +REG32(CXL_DEV_CAP_ARRAY, 0) /* 48b!?!?! */

Also missing a reserved 64 bits to fill in below the device capability headers
which are offset by 0x10

> +    FIELD(CXL_DEV_CAP_ARRAY, CAP_ID, 0, 16)
> +    FIELD(CXL_DEV_CAP_ARRAY, CAP_VERSION, 16, 8)
> +REG32(CXL_DEV_CAP_ARRAY2, 4) /* We're going to pretend it's 64b */
> +    FIELD(CXL_DEV_CAP_ARRAY2, CAP_COUNT, 0, 16)
> +
> +/*
> + * Helper macro to initialize capability headers for CXL devices.
> + *
> + * In the 8.2.8.2, this is listed as a 128b register, but in 8.2.8, it says:
> + * > No registers defined in Section 8.2.8 are larger than 64-bits wide so 
> that
> + * > is the maximum access size allowed for these registers. If this rule is 
> not
> + * > followed, the behavior is undefined
> + *
> + * Here we've chosen to make it 4 dwords. The spec allows any pow2 multiple
> + * access to be used for a register (2 qwords, 8 words, 128 bytes).
> + */
> +#define CXL_DEVICE_CAPABILITY_HEADER_REGISTER(n, offset)                     
>        \
> +    REG32(CXL_DEV_##n##_CAP_HDR0, offset)                 \
> +        FIELD(CXL_DEV_##n##_CAP_HDR0, CAP_ID, 0, 16)      \
> +        FIELD(CXL_DEV_##n##_CAP_HDR0, CAP_VERSION, 16, 8) \
> +    REG32(CXL_DEV_##n##_CAP_HDR1, offset + 4)             \
> +        FIELD(CXL_DEV_##n##_CAP_HDR1, CAP_OFFSET, 0, 32)  \
> +    REG32(CXL_DEV_##n##_CAP_HDR2, offset + 8)             \
> +        FIELD(CXL_DEV_##n##_CAP_HDR2, CAP_LENGTH, 0, 32)
> +
> +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)
> +
> +REG32(CXL_DEV_MAILBOX_CAP, 0)
> +    FIELD(CXL_DEV_MAILBOX_CAP, PAYLOAD_SIZE, 0, 5)
> +    FIELD(CXL_DEV_MAILBOX_CAP, INT_CAP, 5, 1)
> +    FIELD(CXL_DEV_MAILBOX_CAP, BG_INT_CAP, 6, 1)
> +    FIELD(CXL_DEV_MAILBOX_CAP, MSI_N, 7, 4)
> +
> +REG32(CXL_DEV_MAILBOX_CTRL, 4)
> +    FIELD(CXL_DEV_MAILBOX_CTRL, DOORBELL, 0, 1)
> +    FIELD(CXL_DEV_MAILBOX_CTRL, INT_EN, 1, 1)
> +    FIELD(CXL_DEV_MAILBOX_CTRL, BG_INT_EN, 2, 1)

Is it not worth defining the
CXL_DEV_MAILBOX_CMD register for completeness? off set 0x8

> +
> +/* XXX: actually a 64b register */
> +REG32(CXL_DEV_MAILBOX_STS, 0x10)
> +    FIELD(CXL_DEV_MAILBOX_STS, BG_OP, 0, 1)
> +    FIELD(CXL_DEV_MAILBOX_STS, ERRNO, 32, 16)
> +    FIELD(CXL_DEV_MAILBOX_STS, VENDOR_ERRNO, 48, 16)
> +
> +/* XXX: actually a 64b register */
> +REG32(CXL_DEV_BG_CMD_STS, 0x18)
> +    FIELD(CXL_DEV_BG_CMD_STS, BG, 0, 16)
> +    FIELD(CXL_DEV_BG_CMD_STS, DONE, 16, 7)
> +    FIELD(CXL_DEV_BG_CMD_STS, ERRNO, 32, 16)
> +    FIELD(CXL_DEV_BG_CMD_STS, VENDOR_ERRNO, 48, 16)
> +
> +REG32(CXL_DEV_CMD_PAYLOAD, 0x20)
Probably want a comment for this one that it might be huge.

> +
> +#endif