On 11/04/15 22:35, Kinney, Michael D wrote: > Laszlo, > > Yes. They are compatible. And I do recommend switching to > BaseXApicX2ApicLib unconditionally.
Thanks everyone for the feedback, I'll update the patch. Paolo, in case this turns out the only code update after v4 (I can dream...), are you okay if I fix up the patch without posting v5? Thanks Laszlo > > Mike > >> -----Original Message----- >> From: edk2-devel [mailto:edk2-devel-boun...@lists.01.org] On Behalf Of >> Laszlo Ersek >> Sent: Wednesday, November 04, 2015 12:09 PM >> To: Kinney, Michael D; Paolo Bonzini; edk2-de...@ml01.01.org; Fan, Jeff; >> Justen, Jordan L >> Subject: Re: [edk2] [PATCH v4 18/41] OvmfPkg: select LocalApicLib instance >> with x2apic support if SMM_REQUIRE >> >> On 11/04/15 17:55, Kinney, Michael D wrote: >>> Laszlo, >>> >>> BaseXApicX2ApicLib is intended to be used by platforms that support more >>> =256 CPUs. >>> >>> If the current system configuration is < 256 CPUs, then the platform will >> typically stay in APIC mode. If >= 256 CPUs are detected, then X2 APIC mode >> can be enabled using the following API. >>> >>> VOID >>> EFIAPI >>> SetApicMode ( >>> IN UINTN ApicMode >>> ) >>> >>> So just adding BaseXApicX2ApicLib to the DSC does not enable X2 APIC >> mode. You have to add logic to enable X2 APIC mode. >>> >>> I see that QEMU is limited to 255 VCPUs, so the use of BaseXApicLib makes >> sense. Are OVMF configurations supported with >= 256 VCPUs? >> >> I don't think so, but 64-bit Linux guest kernels enable x2apic mode >> anyway, apparently regardless of the VCPU count and topology. >> >> This is normally not a problem, but with SMM support, the APIC library >> gets used (within SMM) *after* Linux configures x2apic mode. This causes >> the "basic" library instance to blow up. Therefore I flipped the library >> class resolution to the one instance that supports x2apic mode, but only >> for the SMM build of OVMF. >> >> So, the question Paolo and I have is *not* whether we must use the >> x2apic-capable library in the SMM build -- that is a fact, forced by the >> X64 Linux guest kernel's behavior. >> >> Neither is our question "how could we enable x2apic mode"? About that, >> we don't care at the moment. :) >> >> Instead, our question is if we can use BaseXApicX2ApicLib even in the >> *non*-SMM build, without fear of regressions. In other words, if >> BaseXApicX2ApicLib can safely replace BaseXApicLib in a build where >> BaseXApicLib would be otherwise fully sufficient. >> >> Because, if the answer is "yes, it is compatible", then we shouldn't >> complicate the library class resolution in the OVMF DSC files, making it >> dependent on the build type (i.e., SMM -> BaseXApicX2ApicLib, non-SMM -> >> BaseXApicLib). Rather than that, we should indiscriminately use >> BaseXApicX2ApicLib. >> >> So... is BaseXApicX2ApicLib compatible with BaseXApicLib in the domain >> where the latter would work sufficiently? >> >> Thanks! >> Laszlo >> >> >>> >>> Thanks, >>> >>> Mike >>> >>>> -----Original Message----- >>>> From: Laszlo Ersek [mailto:ler...@redhat.com] >>>> Sent: Wednesday, November 04, 2015 2:41 AM >>>> To: Paolo Bonzini; edk2-de...@ml01.01.org; Kinney, Michael D; Fan, Jeff; >>>> Justen, Jordan L >>>> Subject: Re: [edk2] [PATCH v4 18/41] OvmfPkg: select LocalApicLib instance >>>> with x2apic support if SMM_REQUIRE >>>> >>>> On 11/04/15 09:48, Paolo Bonzini wrote: >>>>> >>>>> >>>>> On 03/11/2015 22:00, Laszlo Ersek wrote: >>>>>> + >>>>>> +!if $(SMM_REQUIRE) == TRUE >>>>>> + >>>> >> LocalApicLib|UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.inf >>>>>> +!else >>>>>> LocalApicLib|UefiCpuPkg/Library/BaseXApicLib/BaseXApicLib.inf >>>>>> +!endif >>>>>> + >>>>> >>>>> Can we enable BaseXApicX2ApicLib unconditionally? >>>> >>>> I think I am technically capable of that :), but should we? We haven't >>>> used BaseXApicX2ApicLib thus far in OVMF, so I can't predict at all if >>>> it could regress stuff or not. If it causes problems with the >>>> SMM_REQUIRE build, so be it, that's new stuff, but I wanted to avoid >>>> such a global change for the traditional build. >>>> >>>> I'm not against it, I just don't have experience with BaseXApicX2ApicLib. >>>> >>>> Mike, Jeff, Jordan -- what do you think? Why do separate BaseXApicLib >>>> and BaseXApicX2ApicLib instances exist? And why has OvmfPkg always >> used >>>> the former? If it has only been for simplicity's sake, and >>>> BaseXApicX2ApicLib is otherwise widely used internally at Intel, then I >>>> think Paolo is right, and we should just keep the OVMF DSCs simple. >>>> >>>> Thanks >>>> Laszlo >> >> _______________________________________________ >> edk2-devel mailing list >> edk2-devel@lists.01.org >> https://lists.01.org/mailman/listinfo/edk2-devel > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.01.org > https://lists.01.org/mailman/listinfo/edk2-devel > _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
