Re: [PATCH v2 08/12] hw/vmapple/bdif: Introduce vmapple backdoor interface

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Aug 30, 2023 at 04:14:21PM +0000, Alexander Graf wrote:
> The VMApple machine exposes AUX and ROOT block devices (as well as USB OTG
> emulation) via virtio-pci as well as a special, simple backdoor platform
> device.
> 
> This patch implements this backdoor platform device to the best of my
> understanding. I left out any USB OTG parts; they're only needed for
> guest recovery and I don't understand the protocol yet.

Out of curiosity: This interface has no way to check the size of the
block device? I guess that's not necessary in a boot loader that just
parses a boot record and then loads the next stage...

I posted comments below. Otherwise:
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

> 
> Signed-off-by: Alexander Graf <graf@amazon.com>
> 
> ---
> 
> v1 -> v2:
> 
>   - Adapt to system_ss meson.build target
> ---
>  include/hw/vmapple/bdif.h |  31 +++++
>  hw/vmapple/bdif.c         | 245 ++++++++++++++++++++++++++++++++++++++
>  hw/vmapple/Kconfig        |   2 +
>  hw/vmapple/meson.build    |   1 +
>  hw/vmapple/trace-events   |   5 +
>  5 files changed, 284 insertions(+)
>  create mode 100644 include/hw/vmapple/bdif.h
>  create mode 100644 hw/vmapple/bdif.c
> 
> diff --git a/include/hw/vmapple/bdif.h b/include/hw/vmapple/bdif.h
> new file mode 100644
> index 0000000000..65ee43457b
> --- /dev/null
> +++ b/include/hw/vmapple/bdif.h
> @@ -0,0 +1,31 @@
> +/*
> + * VMApple Backdoor Interface
> + *
> + * Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef HW_VMAPPLE_BDIF_H
> +#define HW_VMAPPLE_BDIF_H
> +
> +#include "hw/sysbus.h"
> +#include "qom/object.h"
> +
> +#define TYPE_VMAPPLE_BDIF "vmapple-bdif"
> +OBJECT_DECLARE_SIMPLE_TYPE(VMAppleBdifState, VMAPPLE_BDIF)
> +
> +struct VMAppleBdifState {
> +    /* <private> */
> +    SysBusDevice parent_obj;
> +
> +    /* <public> */
> +    BlockBackend *aux;
> +    BlockBackend *root;
> +    MemoryRegion mmio;
> +};
> +
> +#define VMAPPLE_BDIF_SIZE 0x00200000
> +
> +#endif /* HW_VMAPPLE_BDIF_H */
> diff --git a/hw/vmapple/bdif.c b/hw/vmapple/bdif.c
> new file mode 100644
> index 0000000000..36b5915ff3
> --- /dev/null
> +++ b/hw/vmapple/bdif.c
> @@ -0,0 +1,245 @@
> +/*
> + * VMApple Backdoor Interface
> + *
> + * Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "hw/vmapple/bdif.h"
> +#include "qemu/log.h"
> +#include "qemu/module.h"
> +#include "qapi/error.h"
> +#include "trace.h"
> +#include "hw/block/block.h"
> +#include "sysemu/block-backend.h"
> +
> +#define REG_DEVID_MASK      0xffff0000
> +#define DEVID_ROOT          0x00000000
> +#define DEVID_AUX           0x00010000
> +#define DEVID_USB           0x00100000
> +
> +#define REG_STATUS          0x0
> +#define REG_STATUS_ACTIVE     BIT(0)
> +#define REG_CFG             0x4
> +#define REG_CFG_ACTIVE        BIT(1)
> +#define REG_UNK1            0x8
> +#define REG_BUSY            0x10
> +#define REG_BUSY_READY        BIT(0)
> +#define REG_UNK2            0x400
> +#define REG_CMD             0x408
> +#define REG_NEXT_DEVICE     0x420
> +#define REG_UNK3            0x434
> +
> +typedef struct vblk_sector {
> +    uint32_t pad;
> +    uint32_t pad2;
> +    uint32_t sector;
> +    uint32_t pad3;
> +} VblkSector;
> +
> +typedef struct vblk_req_cmd {
> +    uint64_t addr;
> +    uint32_t len;
> +    uint32_t flags;
> +} VblkReqCmd;
> +
> +typedef struct vblk_req {
> +    VblkReqCmd sector;
> +    VblkReqCmd data;
> +    VblkReqCmd retval;
> +} VblkReq;
> +
> +#define VBLK_DATA_FLAGS_READ  0x00030001
> +#define VBLK_DATA_FLAGS_WRITE 0x00010001
> +
> +#define VBLK_RET_SUCCESS  0
> +#define VBLK_RET_FAILED   1
> +
> +static uint64_t bdif_read(void *opaque, hwaddr offset, unsigned size)
> +{
> +    uint64_t ret = -1;
> +    uint64_t devid = (offset & REG_DEVID_MASK);
> +
> +    switch (offset & ~REG_DEVID_MASK) {
> +    case REG_STATUS:
> +        ret = REG_STATUS_ACTIVE;
> +        break;
> +    case REG_CFG:
> +        ret = REG_CFG_ACTIVE;
> +        break;
> +    case REG_UNK1:
> +        ret = 0x420;
> +        break;
> +    case REG_BUSY:
> +        ret = REG_BUSY_READY;
> +        break;
> +    case REG_UNK2:
> +        ret = 0x1;
> +        break;
> +    case REG_UNK3:
> +        ret = 0x0;
> +        break;
> +    case REG_NEXT_DEVICE:
> +        switch (devid) {
> +        case DEVID_ROOT:
> +            ret = 0x8000000;
> +            break;
> +        case DEVID_AUX:
> +            ret = 0x10000;
> +            break;
> +        }
> +        break;
> +    }
> +
> +    trace_bdif_read(offset, size, ret);
> +    return ret;
> +}
> +
> +static void le2cpu_sector(VblkSector *sector)
> +{
> +    sector->sector = le32_to_cpu(sector->sector);
> +}
> +
> +static void le2cpu_reqcmd(VblkReqCmd *cmd)
> +{
> +    cmd->addr = le64_to_cpu(cmd->addr);
> +    cmd->len = le32_to_cpu(cmd->len);
> +    cmd->flags = le32_to_cpu(cmd->flags);
> +}
> +
> +static void le2cpu_req(VblkReq *req)
> +{
> +    le2cpu_reqcmd(&req->sector);
> +    le2cpu_reqcmd(&req->data);
> +    le2cpu_reqcmd(&req->retval);
> +}
> +
> +static void vblk_cmd(uint64_t devid, BlockBackend *blk, uint64_t value,
> +                     uint64_t static_off)
> +{
> +    VblkReq req;
> +    VblkSector sector;
> +    uint64_t off = 0;
> +    char *buf = NULL;
> +    uint8_t ret = VBLK_RET_FAILED;
> +    int r;
> +
> +    cpu_physical_memory_read(value, &req, sizeof(req));

Please zero req first so that when value is bogus and
cpu_physical_memory_read() does not store to &req, we don't process
req's uninitialized stack memory:

  VblkReq req = {};

> +    le2cpu_req(&req);
> +
> +    if (req.sector.len != sizeof(sector)) {
> +        ret = VBLK_RET_FAILED;
> +        goto out;
> +    }
> +
> +    /* Read the vblk command */
> +    cpu_physical_memory_read(req.sector.addr, &sector, sizeof(sector));

Same here:

  VblkSectors sector = {};

> +    le2cpu_sector(&sector);
> +
> +    off = sector.sector * 512ULL + static_off;
> +
> +    /* Sanity check that we're not allocating bogus sizes */
> +    if (req.data.len > (128 * 1024 * 1024)) {
> +        goto out;
> +    }
> +
> +    buf = g_malloc0(req.data.len);
> +    switch (req.data.flags) {
> +    case VBLK_DATA_FLAGS_READ:
> +        r = blk_pread(blk, off, req.data.len, buf, 0);
> +        trace_bdif_vblk_read(devid == DEVID_AUX ? "aux" : "root",
> +                             req.data.addr, off, req.data.len, r);
> +        if (r < 0) {
> +            goto out;
> +        }
> +        cpu_physical_memory_write(req.data.addr, buf, req.data.len);
> +        ret = VBLK_RET_SUCCESS;
> +        break;
> +    case VBLK_DATA_FLAGS_WRITE:
> +        /* Not needed, iBoot only reads */
> +        break;
> +    default:
> +        break;
> +    }
> +
> +out:
> +    g_free(buf);
> +    cpu_physical_memory_write(req.retval.addr, &ret, 1);
> +}
> +
> +static void bdif_write(void *opaque, hwaddr offset,
> +                       uint64_t value, unsigned size)
> +{
> +    VMAppleBdifState *s = opaque;
> +    uint64_t devid = (offset & REG_DEVID_MASK);
> +
> +    trace_bdif_write(offset, size, value);
> +
> +    switch (offset & ~REG_DEVID_MASK) {
> +    case REG_CMD:
> +        switch (devid) {
> +        case DEVID_ROOT:
> +            vblk_cmd(devid, s->root, value, 0x0);
> +            break;
> +        case DEVID_AUX:
> +            vblk_cmd(devid, s->aux, value, 0x0);
> +            break;
> +        }
> +        break;
> +    }
> +}
> +
> +static const MemoryRegionOps bdif_ops = {
> +    .read = bdif_read,
> +    .write = bdif_write,
> +    .endianness = DEVICE_NATIVE_ENDIAN,
> +    .valid = {
> +        .min_access_size = 1,
> +        .max_access_size = 8,
> +    },
> +    .impl = {
> +        .min_access_size = 1,
> +        .max_access_size = 8,
> +    },
> +};
> +
> +static void bdif_init(Object *obj)
> +{
> +    VMAppleBdifState *s = VMAPPLE_BDIF(obj);
> +
> +    memory_region_init_io(&s->mmio, obj, &bdif_ops, obj,
> +                         "VMApple Backdoor Interface", VMAPPLE_BDIF_SIZE);
> +    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
> +}
> +
> +static Property bdif_properties[] = {
> +    DEFINE_PROP_DRIVE("aux", VMAppleBdifState, aux),
> +    DEFINE_PROP_DRIVE("root", VMAppleBdifState, root),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void bdif_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +
> +    dc->desc = "VMApple Backdoor Interface";
> +    device_class_set_props(dc, bdif_properties);
> +}
> +
> +static const TypeInfo bdif_info = {
> +    .name          = TYPE_VMAPPLE_BDIF,
> +    .parent        = TYPE_SYS_BUS_DEVICE,
> +    .instance_size = sizeof(VMAppleBdifState),
> +    .instance_init = bdif_init,
> +    .class_init    = bdif_class_init,
> +};
> +
> +static void bdif_register_types(void)
> +{
> +    type_register_static(&bdif_info);
> +}
> +
> +type_init(bdif_register_types)
> diff --git a/hw/vmapple/Kconfig b/hw/vmapple/Kconfig
> index a73504d599..388a2bc60c 100644
> --- a/hw/vmapple/Kconfig
> +++ b/hw/vmapple/Kconfig
> @@ -1,3 +1,5 @@
>  config VMAPPLE_AES
>      bool
>  
> +config VMAPPLE_BDIF
> +    bool
> diff --git a/hw/vmapple/meson.build b/hw/vmapple/meson.build
> index bcd4dcb28d..d4624713de 100644
> --- a/hw/vmapple/meson.build
> +++ b/hw/vmapple/meson.build
> @@ -1 +1,2 @@
>  system_ss.add(when: 'CONFIG_VMAPPLE_AES',  if_true: files('aes.c'))
> +system_ss.add(when: 'CONFIG_VMAPPLE_BDIF', if_true: files('bdif.c'))
> diff --git a/hw/vmapple/trace-events b/hw/vmapple/trace-events
> index 03585cdf0f..45c69de2e0 100644
> --- a/hw/vmapple/trace-events
> +++ b/hw/vmapple/trace-events
> @@ -18,3 +18,8 @@ aes_2_read(uint64_t offset, uint64_t res) "offset=0x%"PRIx64" res=0x%"PRIx64
>  aes_2_write_unknown(uint64_t offset) "offset=0x%"PRIx64
>  aes_2_write(uint64_t offset, uint64_t val) "offset=0x%"PRIx64" val=0x%"PRIx64
>  aes_dump_data(const char *desc, const char *hex) "%s%s"
> +
> +# bdif.c
> +bdif_read(uint64_t offset, uint32_t size, uint64_t value) "offset=0x%"PRIx64" size=0x%x value=0x%"PRIx64
> +bdif_write(uint64_t offset, uint32_t size, uint64_t value) "offset=0x%"PRIx64" size=0x%x value=0x%"PRIx64
> +bdif_vblk_read(const char *dev, uint64_t addr, uint64_t offset, uint32_t len, int r) "dev=%s addr=0x%"PRIx64" off=0x%"PRIx64" size=0x%x r=%d"
> -- 
> 2.39.2 (Apple Git-143)
> 
> 
> 
> 
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> 

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