Re: [Qemu-block] [RFC PATCH 6/6] pc: Support firmware configuration with -blockdev

[Laszlo Ersek]

Hi Markus,

On 02/25/19 19:37, Markus Armbruster wrote:
> The PC machines put firmware in ROM by default.  To get it put into
> flash memory (required by OVMF), you have to use -drive
> if=pflash,unit=0,... and optionally -drive if=pflash,unit=1,...
> 
> Why two -drive?  This permits setting up one part of the flash memory
> read-only, and the other part read/write.  Below the hood, it creates
> two separate flash devices, because we were too lazy to improve our
> flash device models to support sector protection.
> 
> The problem at hand is to do the same with -blockdev somehow, as one
> more step towards deprecating -drive.
> 
> Mapping -drive if=none,... to -blockdev is a solved problem.  With
> if=T other than if=none, -drive additionally configures a block device
> frontend.  For non-onboard devices, that part maps to -device.  Also a
> solved problem.  For onboard devices such as PC flash memory, we have
> an unsolved problem.
> 
> This is actually an instance of a wider problem: our general device
> configuration interface doesn't cover onboard devices.  Instead, we
> have a zoo of ad hoc interfaces that are much more limited.  Some of
> them we'd rather deprecate (-drive, -net), but can't until we have
> suitable replacements.
> 
> Sadly, I can't attack the wider problem today.  So back to the narrow
> problem.
> 
> My first idea was to reduce it to its solved buddy by using pluggable
> instead of onboard devices for the flash memory.  Workable, but it
> requires some extra smarts in firmware descriptors and libvirt.  Paolo
> had an idea that is simpler for libvirt: keep the devices onboard, and
> add machine properties for their block backends.
> 
> The implementation is less than straightforward, I'm afraid.
> 
> First, block backend properties are *qdev* properties.  Machines can't
> have those, as they're not devices.  I could duplicate these qdev
> properties as QOM properties, but I hate that.
> 
> More seriously, the properties do not belong to the machine, they
> belong to the onboard flash devices.  Adding them to the machine would
> then require bad magic to somehow transfer them to the flash devices.
> Fortunately, QOM provides the means to handle exactly this case: add
> alias properties to the machine that forward to the onboard devices'
> properties.
> 
> Properties need to be created in .instance_init() methods.  For PC
> machines, that's pc_machine_initfn().  To make alias properties work,
> we need to create the onboard flash devices there, too.  Requires
> several bug fixes, in the previous commits.  We also have to realize
> the devices.  More on that below.
> 
> If the user sets pflash0, firmware resides in flash memory.
> pc_system_firmware_init() maps and realizes the flash devices.
> 
> Else, firmware resides in ROM.  The onboard flash devices aren't used
> then.  pc_system_firmware_init() destroys them unrealized, along with
> the alias properties.  Except I can't figure out how to destroy the
> devices correctly.  Marked FIXME.
> 
> The existing code to pick up drives defined with -drive if=pflash is
> replaced by code to desugar into the machine properties.
> 
> Signed-off-by: Markus Armbruster <address@hidden>
> ---
>  hw/block/pflash_cfi01.c  |   5 +
>  hw/i386/pc.c             |   4 +-
>  hw/i386/pc_sysfw.c       | 230 ++++++++++++++++++++++++++-------------
>  include/hw/block/flash.h |   1 +
>  include/hw/i386/pc.h     |   6 +-
>  5 files changed, 168 insertions(+), 78 deletions(-)

I don't know enough to understand a large part of the commit message. I
can make some (superficial) comments on the code.

In general, the patch looks fine to me.


> diff --git a/hw/block/pflash_cfi01.c b/hw/block/pflash_cfi01.c
> index 6ad27f4472..7c428bbf50 100644
> --- a/hw/block/pflash_cfi01.c
> +++ b/hw/block/pflash_cfi01.c
> @@ -959,6 +959,11 @@ MemoryRegion *pflash_cfi01_get_memory(PFlashCFI01 *fl)
>      return &fl->mem;
>  }
>  
> +BlockBackend *pflash_cfi01_get_blk(PFlashCFI01 *fl)
> +{
> +    return fl->blk;
> +}
> +
>  static void postload_update_cb(void *opaque, int running, RunState state)
>  {
>      PFlashCFI01 *pfl = opaque;
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 3889eccdc3..420a0c5c9e 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -1830,7 +1830,7 @@ void pc_memory_init(PCMachineState *pcms,
>      }
>  
>      /* Initialize PC system firmware */
> -    pc_system_firmware_init(rom_memory, !pcmc->pci_enabled);
> +    pc_system_firmware_init(pcms, rom_memory);
>  
>      option_rom_mr = g_malloc(sizeof(*option_rom_mr));
>      memory_region_init_ram(option_rom_mr, NULL, "pc.rom", PC_ROM_SIZE,
> @@ -2671,6 +2671,8 @@ static void pc_machine_initfn(Object *obj)
>      pcms->smbus_enabled = true;
>      pcms->sata_enabled = true;
>      pcms->pit_enabled = true;
> +
> +    pc_system_flash_create(pcms);
>  }
>  
>  static void pc_machine_reset(void)
> diff --git a/hw/i386/pc_sysfw.c b/hw/i386/pc_sysfw.c
> index 34727c5b1f..98998e1ba8 100644
> --- a/hw/i386/pc_sysfw.c
> +++ b/hw/i386/pc_sysfw.c
> @@ -76,7 +76,58 @@ static void pc_isa_bios_init(MemoryRegion *rom_memory,
>      memory_region_set_readonly(isa_bios, true);
>  }
>  
> -#define FLASH_MAP_UNIT_MAX 2
> +static PFlashCFI01 *pc_pflash_create(const char *name)
> +{
> +    DeviceState *dev = qdev_create(NULL, TYPE_CFI_PFLASH01);
> +
> +    qdev_prop_set_uint64(dev, "sector-length", 4096);
> +    qdev_prop_set_uint8(dev, "width", 1);
> +    qdev_prop_set_string(dev, "name", name);
> +    return CFI_PFLASH01(dev);
> +}
> +
> +void pc_system_flash_create(PCMachineState *pcms)
> +{
> +    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
> +
> +    if (pcmc->pci_enabled) {
> +        pcms->flash[0] = pc_pflash_create("system.flash0");
> +        pcms->flash[1] = pc_pflash_create("system.flash1");
> +        object_property_add_alias(OBJECT(pcms), "pflash0",
> +                                  OBJECT(pcms->flash[0]), "drive",
> +                                  &error_abort);
> +        object_property_add_alias(OBJECT(pcms), "pflash1",
> +                                  OBJECT(pcms->flash[1]), "drive",
> +                                  &error_abort);
> +    }
> +}
> +
> +static void pc_system_flash_cleanup_unused(PCMachineState *pcms)
> +{
> +    char *prop_name;
> +    int i;
> +    Object *dev_obj;
> +
> +    assert(PC_MACHINE_GET_CLASS(pcms)->pci_enabled);
> +
> +    for (i = 0; i < ARRAY_SIZE(pcms->flash); i++) {
> +        dev_obj = OBJECT(pcms->flash[i]);
> +        if (!object_property_get_bool(dev_obj, "realized", &error_abort)) {
> +            prop_name = g_strdup_printf("pflash%d", i);
> +            object_property_del(OBJECT(pcms), prop_name, &error_abort);
> +            g_free(prop_name);
> +            /*
> +             * FIXME delete @dev_obj.  Straight object_unref() is
> +             * wrong, since it leaves dangling references in the
> +             * parent bus behind.  object_unparent() doesn't work,
> +             * either: since @dev_obj hasn't been realized,
> +             * dev_obj->parent is null, and object_unparent() does
> +             * nothing.
> +             */
> +            pcms->flash[i] = NULL;
> +        }
> +    }
> +}

I totally can't recommend a way to resolve this FIXME, alas.

>  
>  /* We don't have a theoretically justifiable exact lower bound on the base
>   * address of any flash mapping. In practice, the IO-APIC MMIO range is
> @@ -84,88 +135,78 @@ static void pc_isa_bios_init(MemoryRegion *rom_memory,
>   * only 18MB-4KB below 4G. For now, restrict the cumulative mapping to 8MB in
>   * size.
>   */
> -#define FLASH_MAP_BASE_MIN ((hwaddr)(4 * GiB - 8 * MiB))
> +#define FLASH_SIZE_LIMIT (8 * MiB)
>  
> -/* This function maps flash drives from 4G downward, in order of their unit
> - * numbers. The mapping starts at unit#0, with unit number increments of 1, 
> and
> - * stops before the first missing flash drive, or before
> - * unit#FLASH_MAP_UNIT_MAX, whichever is reached first.
> +/*
> + * Map the pcms->flash[] from 4GiB downward, and realize.
> + * Map them in descending order, i.e. pcms->flash[0] at the top,
> + * without gaps.
> + * Stop at the first pcms->flash[0] lacking a block backend.
> + * Set each flash's size from its block backend.  Fatal error if the
> + * size isn't a non-zero multiples of 4KiB, or the total size exceeds
> + * FLASH_SIZE_LIMIT.
>   *
> - * Addressing within one flash drive is of course not reversed.
> - *
> - * An error message is printed and the process exits if:
> - * - the size of the backing file for a flash drive is non-positive, or not a
> - *   multiple of the required sector size, or
> - * - the current mapping's base address would fall below FLASH_MAP_BASE_MIN.
> - *
> - * The drive with unit#0 (if available) is mapped at the highest address, and
> - * it is passed to pc_isa_bios_init(). Merging several drives for isa-bios is
> + * If pcms->flash[0] has a block backend, its memory is passed to
> + * pc_isa_bios_init().  Merging several flash devices for isa-bios is
>   * not supported.
>   */
> -static void pc_system_flash_init(MemoryRegion *rom_memory)
> +static void pc_system_flash_map(PCMachineState *pcms,
> +                                MemoryRegion *rom_memory)
>  {
> -    int unit;
> -    DriveInfo *pflash_drv;
> +    hwaddr total_size = 0;
> +    int i;
>      BlockBackend *blk;
>      int64_t size;
> -    char *fatal_errmsg = NULL;
> -    hwaddr phys_addr = 0x100000000ULL;
>      uint32_t sector_size = 4096;

(1) Rather than duplicate this constant here, can we get it inside the
loop, via the "sector-length" property? We set the property in
pc_pflash_create() (identically for both chips, but that's not a problem
I think).

>      PFlashCFI01 *system_flash;
>      MemoryRegion *flash_mem;
> -    char name[64];
>      void *flash_ptr;
>      int ret, flash_size;
>  
> -    for (unit = 0;
> -         (unit < FLASH_MAP_UNIT_MAX &&
> -          (pflash_drv = drive_get(IF_PFLASH, 0, unit)) != NULL);
> -         ++unit) {
> -        blk = blk_by_legacy_dinfo(pflash_drv);
> +    assert(PC_MACHINE_GET_CLASS(pcms)->pci_enabled);
> +
> +    for (i = 0; i < ARRAY_SIZE(pcms->flash); i++) {
> +        system_flash = pcms->flash[i];
> +        blk = pflash_cfi01_get_blk(system_flash);
> +        if (!blk) {
> +            break;
> +        }
>          size = blk_getlength(blk);
>          if (size < 0) {
> -            fatal_errmsg = g_strdup_printf("failed to get backing file 
> size");
> -        } else if (size == 0) {
> -            fatal_errmsg = g_strdup_printf("PC system firmware (pflash) "
> -                               "cannot have zero size");
> -        } else if ((size % sector_size) != 0) {
> -            fatal_errmsg = g_strdup_printf("PC system firmware (pflash) "
> -                               "must be a multiple of 0x%x", sector_size);
> -        } else if (phys_addr < size || phys_addr - size < 
> FLASH_MAP_BASE_MIN) {
> -            fatal_errmsg = g_strdup_printf("oversized backing file, pflash "
> -                               "segments cannot be mapped under "
> -                               TARGET_FMT_plx, FLASH_MAP_BASE_MIN);
> +            error_report("can't get size of block device %s: %s",
> +                         blk_name(blk), strerror(-size));
> +            exit(1);
>          }
> -        if (fatal_errmsg != NULL) {
> -            Location loc;
> -
> -            /* push a new, "none" location on the location stack; overwrite 
> its
> -             * contents with the location saved in the option; print the 
> error
> -             * (includes location); pop the top
> -             */
> -            loc_push_none(&loc);
> -            if (pflash_drv->opts != NULL) {
> -                qemu_opts_loc_restore(pflash_drv->opts);
> -            }
> -            error_report("%s", fatal_errmsg);
> -            loc_pop(&loc);
> -            g_free(fatal_errmsg);
> +        if (size == 0) {
> +            error_report("system firmware block device %s is empty",
> +                         blk_name(blk));
> +            exit(1);
> +        }
> +        if (size == 0 || size % sector_size != 0) {

(2) The (size == 0) condition is superfluous here, it's been checked
just above.


> +            error_report("system firmware block device %s has invalid size "
> +                         "%" PRId64,
> +                         blk_name(blk), size);
> +            info_report("its size must be a non-zero multiple of 0x%x",
> +                        sector_size);
> +            exit(1);
> +        }
> +        if ((hwaddr)size != size
> +            || total_size > HWADDR_MAX - size
> +            || total_size + size > FLASH_SIZE_LIMIT) {
> +            error_report("combined size of system firmware exceeds "
> +                         "%" PRIu64 " bytes",
> +                         FLASH_SIZE_LIMIT);
>              exit(1);
>          }
>  
> -        phys_addr -= size;
> +        total_size += size;
> +        qdev_prop_set_uint32(DEVICE(system_flash), "num-blocks",
> +                             size / sector_size);

OK, this division looks safe (the quotient should fit in a uint32_t
property) due to the FLASH_SIZE_LIMIT check above.

> +        qdev_init_nofail(DEVICE(system_flash));
> +        sysbus_mmio_map(SYS_BUS_DEVICE(system_flash), 0,
> +                        0x100000000ULL - total_size);
>  
> -        /* pflash_cfi01_register() creates a deep copy of the name */
> -        snprintf(name, sizeof name, "system.flash%d", unit);
> -        system_flash = pflash_cfi01_register(phys_addr, name,
> -                                             size, blk, sector_size,
> -                                             1      /* width */,
> -                                             0x0000 /* id0 */,
> -                                             0x0000 /* id1 */,
> -                                             0x0000 /* id2 */,
> -                                             0x0000 /* id3 */,
> -                                             0      /* be */);
> -        if (unit == 0) {
> +        if (i == 0) {
>              flash_mem = pflash_cfi01_get_memory(system_flash);
>              pc_isa_bios_init(rom_memory, flash_mem, size);
>  
> @@ -236,24 +277,63 @@ static void old_pc_system_rom_init(MemoryRegion 
> *rom_memory, bool isapc_ram_fw)
>                                  bios);
>  }
>  
> -void pc_system_firmware_init(MemoryRegion *rom_memory, bool isapc_ram_fw)
> +void pc_system_firmware_init(PCMachineState *pcms,
> +                             MemoryRegion *rom_memory)
>  {
> +    PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
> +    int i;
>      DriveInfo *pflash_drv;
> +    BlockBackend *pflash_blk[ARRAY_SIZE(pcms->flash)];
> +    Location loc;
>  
> -    pflash_drv = drive_get(IF_PFLASH, 0, 0);
> -
> -    if (isapc_ram_fw || pflash_drv == NULL) {
> -        /* When a pflash drive is not found, use rom-mode */
> -        old_pc_system_rom_init(rom_memory, isapc_ram_fw);
> +    if (!pcmc->pci_enabled) {
> +        old_pc_system_rom_init(rom_memory, true);
>          return;
>      }
>  
> -    if (kvm_enabled() && !kvm_readonly_mem_enabled()) {
> -        /* Older KVM cannot execute from device memory. So, flash memory
> -         * cannot be used unless the readonly memory kvm capability is 
> present. */
> -        fprintf(stderr, "qemu: pflash with kvm requires KVM readonly memory 
> support\n");
> -        exit(1);
> +    /* Map legacy -drive if=pflash to machine properties */
> +    for (i = 0; i < ARRAY_SIZE(pcms->flash); i++) {
> +        pflash_blk[i] = pflash_cfi01_get_blk(pcms->flash[i]);
> +        pflash_drv = drive_get(IF_PFLASH, 0, i);
> +        if (!pflash_drv) {
> +            continue;
> +        }
> +        loc_push_none(&loc);
> +        qemu_opts_loc_restore(pflash_drv->opts);
> +        if (pflash_blk[i]) {
> +            error_report("clashes with -machine");
> +            exit(1);
> +        }
> +        pflash_blk[i] = blk_by_legacy_dinfo(pflash_drv);
> +        qdev_prop_set_drive(DEVICE(pcms->flash[i]),
> +                            "drive", pflash_blk[i], &error_fatal);
> +        loc_pop(&loc);
>      }
>  
> -    pc_system_flash_init(rom_memory);
> +    /* Reject gaps */
> +    for (i = 1; i < ARRAY_SIZE(pcms->flash); i++) {
> +        if (pflash_blk[i] && !pflash_blk[i - 1]) {
> +            error_report("pflash%d requires pflash%d", i, i - 1);
> +            exit(1);
> +        }
> +    }
> +
> +    if (!pflash_blk[0]) {
> +        /* Machine property pflash0 not set, use ROM mode */
> +        old_pc_system_rom_init(rom_memory, false);
> +    } else {
> +        if (kvm_enabled() && !kvm_readonly_mem_enabled()) {
> +            /*
> +             * Older KVM cannot execute from device memory. So, flash
> +             * memory cannot be used unless the readonly memory kvm
> +             * capability is present.
> +             */
> +            error_report("pflash with kvm requires KVM readonly memory 
> support");
> +            exit(1);
> +        }
> +
> +        pc_system_flash_map(pcms, rom_memory);
> +    }
> +
> +    pc_system_flash_cleanup_unused(pcms);
>  }
> diff --git a/include/hw/block/flash.h b/include/hw/block/flash.h
> index 24b13eb525..91e0f8dd6e 100644
> --- a/include/hw/block/flash.h
> +++ b/include/hw/block/flash.h
> @@ -22,6 +22,7 @@ PFlashCFI01 *pflash_cfi01_register(hwaddr base,
>                                     uint16_t id0, uint16_t id1,
>                                     uint16_t id2, uint16_t id3,
>                                     int be);
> +BlockBackend *pflash_cfi01_get_blk(PFlashCFI01 *fl);
>  MemoryRegion *pflash_cfi01_get_memory(PFlashCFI01 *fl);
>  
>  /* pflash_cfi02.c */
> diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
> index 3ff127ebd0..266639ca8c 100644
> --- a/include/hw/i386/pc.h
> +++ b/include/hw/i386/pc.h
> @@ -6,6 +6,7 @@
>  #include "hw/boards.h"
>  #include "hw/isa/isa.h"
>  #include "hw/block/fdc.h"
> +#include "hw/block/flash.h"
>  #include "net/net.h"
>  #include "hw/i386/ioapic.h"
>  
> @@ -39,6 +40,7 @@ struct PCMachineState {
>      PCIBus *bus;
>      FWCfgState *fw_cfg;
>      qemu_irq *gsi;
> +    PFlashCFI01 *flash[2];
>  
>      /* Configuration options: */
>      uint64_t max_ram_below_4g;
> @@ -278,8 +280,8 @@ extern PCIDevice *piix4_dev;
>  int piix4_init(PCIBus *bus, ISABus **isa_bus, int devfn);
>  
>  /* pc_sysfw.c */
> -void pc_system_firmware_init(MemoryRegion *rom_memory,
> -                             bool isapc_ram_fw);
> +void pc_system_flash_create(PCMachineState *pcms);
> +void pc_system_firmware_init(PCMachineState *pcms, MemoryRegion *rom_memory);
>  
>  /* acpi-build.c */
>  void pc_madt_cpu_entry(AcpiDeviceIf *adev, int uid,
> 

Looks like a careful conversion to me (although I certainly miss the
finer aspects of DriveInfo vs. BlockBackend, etc).

Thanks,
Laszlo