Gleb Natapov wrote:
> Currently HPET ACPI table is created regardless of whether qemu actually
> created hpet device. This may confuse some guests that don't check that
> hpet is functional before using it. Solve this by passing info about
> hpets in qemu to seabios via fw config interface. Additional benefit is
> that seabios no longer uses hard coded hpet configuration. Proposed
> interface supports up to 256 hpets. This is the number defined by hpet 
> spec.

Nice, this lays the ground for adding hpets via -device.

(But I think I read there can only be 8 hpets with a total sum of 256
timers.)

> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
> diff --git a/hw/hpet.c b/hw/hpet.c
> index 93fc399..f2a4514 100644
> --- a/hw/hpet.c
> +++ b/hw/hpet.c
> @@ -73,6 +73,8 @@ typedef struct HPETState {
>      uint64_t hpet_counter;      /* main counter */
>  } HPETState;
>  
> +struct hpet_fw_config hpet_cfg = {.valid = 1};
> +
>  static uint32_t hpet_in_legacy_mode(HPETState *s)
>  {
>      return s->config & HPET_CFG_LEGACY;
> @@ -661,6 +663,9 @@ static void hpet_reset(DeviceState *d)
>           */
>          hpet_pit_enable();
>      }
> +    hpet_cfg.count = 1;
> +    hpet_cfg.hpet.event_timer_block_id = (uint32_t)s->capability;

The number of timers, thus the content of capability can change on
vmload. So you need to update hpet_cfg there as well.

And I think we can move the capability setup into init. But this is not
directly related to this patch, would just avoid adding this hunk to
hpet_reset.

> +    hpet_cfg.hpet.address = sysbus_from_qdev(d)->mmio[0].addr;
>      count = 1;
>  }
>  
> diff --git a/hw/hpet_emul.h b/hw/hpet_emul.h
> index d7bc102..5cf5463 100644
> --- a/hw/hpet_emul.h
> +++ b/hw/hpet_emul.h
> @@ -53,4 +53,20 @@
>  #define HPET_TN_INT_ROUTE_CAP_SHIFT 32
>  #define HPET_TN_CFG_BITS_READONLY_OR_RESERVED 0xffff80b1U
>  
> +struct hpet_fw_entry
> +{
> +    uint32_t event_timer_block_id;
> +    uint64_t address;
> +    uint16_t min_tick;
> +    uint8_t page_prot;
> +} __attribute__ ((packed));
> +
> +struct hpet_fw_config
> +{
> +    uint8_t valid;
> +    uint8_t count;
> +    struct hpet_fw_entry hpet;

Why not already struct hpet_fw_entry hpet[8]? Once the bios bits are
merge, we can quickly remove the single hpet limitation on qemu side.

> +} __attribute__ ((packed));
> +
> +extern struct hpet_fw_config hpet_cfg;
>  #endif
> diff --git a/hw/pc.c b/hw/pc.c
> index 1491129..d14d657 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -61,6 +61,7 @@
>  #define FW_CFG_SMBIOS_ENTRIES (FW_CFG_ARCH_LOCAL + 1)
>  #define FW_CFG_IRQ0_OVERRIDE (FW_CFG_ARCH_LOCAL + 2)
>  #define FW_CFG_E820_TABLE (FW_CFG_ARCH_LOCAL + 3)
> +#define FW_CFG_HPET (FW_CFG_ARCH_LOCAL + 4)
>  
>  #define E820_NR_ENTRIES		16
>  
> @@ -484,6 +485,8 @@ static void *bochs_bios_init(void)
>      fw_cfg_add_bytes(fw_cfg, FW_CFG_E820_TABLE, (uint8_t *)&e820_table,
>                       sizeof(struct e820_table));
>  
> +    fw_cfg_add_bytes(fw_cfg, FW_CFG_HPET, (uint8_t *)&hpet_cfg,
> +                     sizeof(struct hpet_fw_config));
>      /* allocate memory for the NUMA channel: one (64bit) word for the number
>       * of nodes, one word for each VCPU->node and one word for each node to
>       * hold the amount of memory.
> --
> 			Gleb.
> 
> 

Jan