On 10/04/19 13:31, Igor Mammedov wrote: > On Tue, 1 Oct 2019 20:03:20 +0200 > "Laszlo Ersek" <ler...@redhat.com> wrote:
>> (1) What values to use. > SeaBIOS writes 0x00 into command port, but it seems that's taken by > EFI_SMM_COMMUNICATION_PROTOCOL. So we can use the next unused value > (lets say 0x4). We probably don't have to use status port or > EFI_SMM_COMMUNICATION_PROTOCOL, since the value of written into 0xB2 > is sufficient to distinguish hotplug event. Thanks. Can you please write a QEMU patch for the ACPI generator such that hotplugging a VCPU writes value 4 to IO port 0xB2? That will allow me to experiment with OVMF. (I can experiment with some other parts in edk2 even before that.) >> (2) How the parameters are passed. >> >> >> (2a) For the new CPU, the SMI remains pending, until it gets an >> INIT-SIPI-SIPI from one of the previously plugged CPUs (most likely, the >> BSP). At that point, the new CPU will execute the "initial SMI handler >> for hotplugged CPUs", at the default SMBASE. >> >> That's a routine we'll have to write in assembly, from zero. In this >> routine, we can read back IO ports 0xB2 and 0xB3. And QEMU will be happy >> to provide the values last written (see apm_ioport_readb() in >> "hw/isa/apm.c"). So we can receive the values in this routine. Alright. > > Potentially we can can avoid writing custom SMI handler, > what do you think about following workflow: > > on system boot after initial CPUs relocation, firmware set NOP SMI handler > at default SMBASE. > Then as reaction to GPE triggered SMI (on cpu hotplug), after SMI rendezvous, > a host cpu reads IO port 0xB2 and does hotplugged CPUs enumeration. > > a) assuming we allow hotplug only in case of negotiated SMI broadcast > host CPU shoots down all in-flight INIT/SIPI/SIPI for hotpugged CPUs > to avoid race within relocation handler. How is that "shootdown" possible? > After that host CPU in loop > > b) it prepares/initializes necessary CPU structures for a hotplugged > CPU if necessary and replaces NOP SMI handler with the relocation > SMI handler that is used during system boot. > > c) a host CPU sends NOP INIT/SIPI/SIPI to the hotplugged CPU > > d) the woken up hotplugged CPU, jumps to default SMBASE and > executes hotplug relocation handler. > > e) after the hotplugged CPU is relocated and if there are more > hotplugged CPUs, a host CPU repeats b-d steps for the next > hotplugged CPU. > > f) after all CPUs are relocated, restore NOP SMI handler at default > SMBASE. > Thanks Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#48503): https://edk2.groups.io/g/devel/message/48503 Mute This Topic: https://groups.io/mt/34201782/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
