Hi Salil,
Thanks for this, I've fixed a couple of bugs in the tree.
On the qemu side: Using KVM and your Qemu tree, PSCI returns success, when it should return denied for CPUs that are forbidden due to firmware policy: [ 0.027597] smp: Bringing up secondary CPUs ... [ 5.108204] CPU1: failed to come online [ 5.109198] CPU1: failed in unknown state : 0x0 [ 5.110384] smp: Brought up 1 node, 1 CPU
This is mostly harmless for linux, but using PSCI_DENIED squashes the error, and avoids the timeout waiting for the secondary to turn up. Mostly harmless as this may cause 'cpus stuck in kernel' to get set, which would prevent kexec.
This probably means you're not using the HVC_TO_USER support for KVM that gets added as part of this series. You can then use the PSCI_TO_USER cap to disable the kernel's PSCI handler, which lets the VMM manage this directly.
Still using KVM, firmware should clear the enabled bit from _STA for any call after the eject-request. I see this is still 0xF before _EJx is called. This means the cpu remains registered, and user-space doesn't get notified that the CPU is no longer available. User-space can still try to enable the CPU, which will fail.
I've not tried TCG mode yet.
Thanks,
James
On 17/10/2022 17:12, Salil Mehta via Linaro-open-discussions wrote:
Hi James, As discussed in the meeting below are the repositories which you might want to have a look.
[1] Forward ported QEMU with some fixes was shared (by Salil) https://github.com/salil-mehta/qemu.git virt-cpuhp-armv8/rfc-v1-port29092022
[2] James Approach with online-capable and present==possible (some fixes) https://github.com/salil-mehta/linux.git virt-cpuhp-arm64/rfc-v2/jmorse-pres-eq-poss-cpu
[3] Variant of James approach with online-capable and conditionally present cpus https://github.com/salil-mehta/linux.git virt-cpuhp-arm64/rfc-v2/jmorse-variant-with-cond-present-cpu
I have also shared the LOD presentation with Joyce for uploading to the site.
Attachment: [1] Linaro Open Discussion Meeting Update - 05102022 - Salil_Mehta-fixed.pdf
Many thanks Salil
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