[26.04_linux-nvidia-bos] Vera: Backporting removal of extra ISBs when using msr_hcr_el2 - #534
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PR Validation ReportPatchscan ✅ No Missing FixesAll cherry-picked commits checked — no missing upstream fixes found. PR Lint ✅ All checks passedDetailsChecking 1 commits... Cherry-pick digest: ┌──────────────┬──────────────────────────────────────────────────────────────────┬────────────┬─────────┬───────────────────────────┐ │ Local │ Referenced upstream / Patch subject │ Patch-ID │ Subject │ SoB chain │ ├──────────────┼──────────────────────────────────────────────────────────────────┼────────────┼─────────┼───────────────────────────┤ │ 281813fa9655 │ 54a3cc145456 KVM: arm64: Remove extra ISBs when using msr_hcr_el │ match │ match │ preserved + emilys added │ └──────────────┴──────────────────────────────────────────────────────────────────┴────────────┴─────────┴───────────────────────────┘ Lint: all checks passed. |
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The msr_hcr_el2 macro is slightly awkward, as it provides an ISB when CONFIG_AMPERE_ERRATUM_AC04_CPU_23 is present, and none otherwise. Note that this this option is 'default y', meaning that it is likely to be selected. Most instances of msr_hcr_el2 are also immediately followed by an ISB, meaning that in most cases, you end-up with two back-to-back ISBs. This isn't a big deal, but once you have seen that, you can't unsee it. Rework the msr_hcr_el2 macro to always provide the ISB, and drop the superfluous ISBs everywhere else. Reviewed-by: Fuad Tabba <tabba@google.com> Tested-by: Fuad Tabba <tabba@google.com> Link: https://patch.msgid.link/20260321212419.2803972-6-maz@kernel.org Signed-off-by: Marc Zyngier <maz@kernel.org> (cherry picked from commit 54a3cc1) Signed-off-by: Emily Soto <emilys@nvidia.com>
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LGTM!
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nirmoy
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Merged, closing PR. |
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Backport of 54a3cc145456272b10c1452fe89e1dcf933d5c39, which removes redundant ISBs after msr_hcr_el2, so HCR_EL2 writes do one barrier instead of two and run a bit faster. Verified that patch is present in kernel using check-hcr-isb.sh.
Script output:
Launchpad: https://bugs.launchpad.net/ubuntu/+source/linux-nvidia-bos/+bug/2163052