On Mon, Apr 23, 2012 at 01:27:40PM +0200, Vasilis Liaskovitis wrote:
On Sun, Apr 22, 2012 at 04:58:47PM +0300, Gleb Natapov wrote:
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.
i see, that is a simpler solution. Since qemu currently creates most ram e820map
Quite the contrary. Qemu creates only one entry that Seabios can't figure by itself.
entries and passes them to seabios, I tried to follow the same approach. But your suggestion makes things easier and we don't have to worry about merged e820 entries on hot-remove. I 'll rework it. thanks,
Vasilis
-- Gleb.