New subject: [RFC PATCH 8/9] pc: adjust e820 map on hot-add and hot-remove

22 Apr 2012

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@profitbricks.com
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.

    

Re: [SeaBIOS] [RFC PATCH 8/9] pc: adjust e820 map on hot-add and hot-remove

Signed-off-by: Vasilis Liaskovitis vasilis.liaskovitis@profitbricks.com

#endif