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.
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
--
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