On 10/08/19 13:35, Ard Biesheuvel wrote: > On Tue, 8 Oct 2019 at 13:27, Laszlo Ersek <ler...@redhat.com> wrote: >> >> Repo: https://github.com/lersek/edk2.git >> Branch: max_cpus_bz_1515 >> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1515 >> >> UefiCpuPkg/MpInitLib currently lacks support for the following use case: >> >> - time-limited AP enumeration is not reliable on the platform >> (individual AP check-in may take arbitrarily long), and >> >> - APs may finish the wakeup routine, and report in to the BSP, in any >> sequence whatsoever, and >> >> - the number of boot CPUs (which is known in advance) is strictly less >> than the number of maximum CPUs (which is also known in advance). >> >> In the above case, the platform cannot tell UefiCpuPkg/MpInitLib to wait >> exactly until all boot APs check in. That is, the platform can't request >> that the AP enumeration never time out, but also not wait for too long. >> >> For supporting this use case, the patch series introduces >> PcdCpuBootLogicalProcessorNumber to UefiCpuPkg, and makes MpInitLib wait >> for exactly that many CPUs (= BSP + APs) to show up during CPU >> enumeration. >> >> Working towards VCPU hotplug with OVMF, OvmfPkg/PlatformPei fetches both >> the boot and the max CPU counts from QEMU, co-operating with the >> following QEMU patch set: >> >> [qemu-devel] [PATCH 0/4] hw/i386: pass "MachineState.smp.max_cpus" to OVMF >> http://mid.mail-archive.com/20191008105259.5378-1-lersek@redhat.com >> >> and passes them to UefiCpuPkg via PcdCpuBootLogicalProcessorNumber and >> PcdCpuMaxLogicalProcessorNumber. >> >> As a result, PcdCpuApInitTimeOutInMicroSeconds becomes irrelevant for, >> and unused by, OVMF -- time-limited AP enumeration is never going to be >> used. >> >> When OVMF is built with -D SMM_REQUIRE, this patch series is just a >> small building block, towards the full VCPU hotplug feature. However, >> when OVMF is built without -D SMM_REQUIRE, this series (together with >> the counterpart patch set for QEMU) completes the VCPU hotplug feature: >> it allows S3 resume to work with VCPUs hot-plugged previously (at OS >> runtime, of course). >> >> Cc: Anthony Perard <anthony.per...@citrix.com> >> Cc: Ard Biesheuvel <ard.biesheu...@linaro.org> >> Cc: Eric Dong <eric.d...@intel.com> >> Cc: Igor Mammedov <imamm...@redhat.com> >> Cc: Jordan Justen <jordan.l.jus...@intel.com> >> Cc: Julien Grall <julien.gr...@arm.com> >> Cc: Ray Ni <ray...@intel.com> >> >> Thanks >> Laszlo >> >> Laszlo Ersek (4): >> UefiCpuPkg/MpInitLib: honor the platform's boot CPU count in AP >> detection > > Assuming this ^^^ patch gets accepted by the maintainers, > >> OvmfPkg/OvmfXen.dsc: remove PcdCpu* dynamic defaults >> OvmfPkg/IndustryStandard: define FW_CFG_X86_TOPOLOGY structure type >> OvmfPkg/PlatformPei: rewrite MaxCpuCountInitialization() for CPU >> hotplug >> > > Acked-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > > for the OvmfPkg changes. >
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