On Thu, Apr 19, 2012 at 04:08:46PM +0200, Vasilis Liaskovitis wrote:
> Hotplugged memory is not persistent in the e820 memory maps. After hotplugging
> a memslot and rebooting the VM, the hotplugged device is not present.
>
> A possible solution is to add an e820 for the new memslot in the acpi_piix4
> hot-add handler. On a reset, Seabios (see next patch in series) will enable all
> memory devices for which it finds an e820 entry that covers the devices's address
> range.
>
> On hot-remove, the acpi_piix4 handler will try to remove the e820 entry
> corresponding to the device. This will work when no VM reboots happen
> between hot-add and hot-remove, but it is not a sufficient solution in
> general: Seabios and GuestOS merge adjacent e820 entries on machine reboot,
> so the sequence hot-add/ rebootVM / hot-remove will fail to remove a
> corresponding e820 entry at the hot-remove phase.
>
Why do you need this path and the next one? Bios can restore the state
of memslots and build e820 map by reading mems_sts.
> Signed-off-by: Vasilis Liaskovitis <vasilis.liaskovitis@xxxxxxxxxxxxxxxx>
> ---
> hw/acpi_piix4.c | 6 ++++++
> hw/pc.c | 28 ++++++++++++++++++++++++++++
> hw/pc.h | 1 +
> 3 files changed, 35 insertions(+), 0 deletions(-)
>
> diff --git a/hw/acpi_piix4.c b/hw/acpi_piix4.c
> index 2921d18..2b5fd04 100644
> --- a/hw/acpi_piix4.c
> +++ b/hw/acpi_piix4.c
> @@ -619,6 +619,9 @@ static void piix4_memslot_eject(uint32_t addr, uint32_t val)
> s = memslot_find_from_idx(start + idx);
> assert(s != NULL);
> memslot_depopulate(s);
> + if (e820_del_entry(s->start, s->size, E820_RAM) == -EBUSY)
> + PIIX4_DPRINTF("failed to remove e820 entry for memslot %u\n",
> + s->idx);
> }
> val = val >> 1;
> idx++;
> @@ -634,6 +637,9 @@ static int piix4_memslot_hotplug(DeviceState *qdev, SysBusDevice *dev, int
>
> if (add) {
> enable_mem_device(s, slot->idx);
> + if (e820_add_entry(slot->start, slot->size, E820_RAM) == -EBUSY)
> + PIIX4_DPRINTF("failed to add e820 entry for memslot %u\n",
> + slot->idx);
> }
> else {
> disable_mem_device(s, slot->idx);
> diff --git a/hw/pc.c b/hw/pc.c
> index f1f550a..04d243f 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -593,6 +593,34 @@ int e820_add_entry(uint64_t address, uint64_t length, uint32_t type)
> return index;
> }
>
> +int e820_del_entry(uint64_t address, uint64_t length, uint32_t type)
> +{
> + int index = le32_to_cpu(e820_table.count);
> + int search;
> + struct e820_entry *entry;
> +
> + if (index == 0)
> + return -EBUSY;
> + search = index - 1;
> + entry = &e820_table.entry[search];
> + while (search >= 0) {
> + if ((entry->address == cpu_to_le64(address)) &&
> + (entry->length == cpu_to_le64(length)) &&
> + (entry->type == cpu_to_le32(type))){
> + if (search != index - 1) {
> + memcpy(&e820_table.entry[search], &e820_table.entry[search + 1],
> + sizeof(struct e820_entry) * (index - search));
> + }
> + index--;
> + e820_table.count = cpu_to_le32(index);
> + return 1;
> + }
> + search--;
> + entry = &e820_table.entry[search];
> + }
> + return -EBUSY;
> +}
> +
> static void bochs_bios_setup_hp_memslots(uint64_t *fw_cfg_slots);
>
> static void *bochs_bios_init(void)
> diff --git a/hw/pc.h b/hw/pc.h
> index 74d3369..4925e8c 100644
> --- a/hw/pc.h
> +++ b/hw/pc.h
> @@ -226,5 +226,6 @@ void pc_system_firmware_init(MemoryRegion *rom_memory);
> #define E820_UNUSABLE 5
>
> int e820_add_entry(uint64_t, uint64_t, uint32_t);
> +int e820_del_entry(uint64_t, uint64_t, uint32_t);
>
> #endif
> --
> 1.7.9
--
Gleb.
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