Re: [PATCH v2 0/3] KVM: selftests: arm64: Make sea_to_user skip cleanly

[Jiaqi Yan]

On Tue, Aug 18, 2026 at 4:29 AM Like Xu <like.xu.linux@xxxxxxxxx> wrote:
>
> This series hardens the arm64 sea_to_user selftest so that it reports a
> clean skip on hosts that cannot actually run it, instead of aborting or
> silently passing.
>
> The test drives a real recoverable memory UER through APEI EINJ and
> expects the guest to consume the poison and exit to userspace with
> KVM_EXIT_ARM_SEA. That relies on host and firmware support that is not
> present everywhere, and each unmet dependency is now turned into a skip:
>
>   - EINJ injection is driven directly through debugfs, and an unusable
>     EINJ (not built, no firmware support, or not running as root) is
>     classified from errno and skipped rather than mishandled.
>   - Guest memory is backed by 1GB hugepages; with an empty pool the test
>     now skips up front instead of failing an mmap() with -ENOMEM.
>   - Some firmware only arms EINJ poison as part of the trigger step that
>     notrigger=1 skips, so nothing consumable is left for the guest to
>     read. That case is detected and skipped rather than reported as a
>     spurious KVM_EXIT_MMIO failure.

Thanks for these fixes. Just wonder, do you mind also integrating two
previous fix attempts in [*] into this series:
1. Refactor run_vm to catch GUEST_FAIL, instead of causing confusing
unhandled MMIO kvm exit.
2. Sync far_invalid to guest.

, given the high level goal is to harden sea_to_user.c?

The first one will make the test result less confusing for the runner.
The 2nd one improves readability. You can re-use my code in the patch.

[*] https://lore.kernel.org/kvmarm/20260130192837.890688-1-jiaqiyan@xxxxxxxxxx

>
> Tested on an arm64 host with CONFIG_ACPI_APEI_EINJ: on a platform whose
> firmware places no consumable poison under notrigger=1 the test now
> skips cleanly, and the earlier -ENOMEM and abort paths are gone.
>
> v1 [1] was a single patch doing only the 1GB hugepage check. Following
> Marc's review [2], it is expanded into a series that also fixes the EINJ
> handling the test depends on.
>
> Test Results:
>
>   Case 1 (echo 0 > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages):
>
>   # timeout set to 120
>   # selftests: kvm: sea_to_user
>   # Random seed: 0x6b8b4567
>   # 1..0 # SKIP - Requirement not met: get_free_hugepages(backing_page_size) >= VM_MEM_SIZE
>   ok 1 selftests: kvm: sea_to_user # SKIP
>   # 1 skipped test(s) detected.  Consider enabling relevant config options to improve coverage.
>   # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
>
>   Case 2 (rmmod einj):
>
>   # selftests: kvm: sea_to_user
>   # Random seed: 0x6b8b4567
>   # # Mapped 0x40000 pages: gva=0x80000000 to gpa=0xff80000000
>   # # Before EINJect: data=0xbaadcafe
>   # # EINJ_GVA=0x81234bad, einj_gpa=0xff81234bad, einj_hva=0xffff41234bad, einj_hpa=0x42c1234bad
>   # 1..0 # SKIP need CONFIG_ACPI_APEI_EINJ and firmware EINJ support
>   ok 1 selftests: kvm: sea_to_user # SKIP
>   # 1 skipped test(s) detected.  Consider enabling relevant config options to improve coverage.
>   # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
>
>   Case 3 (modprobe einj):
>
>   # selftests: kvm: sea_to_user
>   # Random seed: 0x6b8b4567
>   # # Mapped 0x40000 pages: gva=0x80000000 to gpa=0xff80000000
>   # # Before EINJect: data=0xbaadcafe
>   # # EINJ_GVA=0x81234bad, einj_gpa=0xff81234bad, einj_hva=0xffff41234bad, einj_hpa=0x42c1234bad
>   # # 0x10 > /sys/kernel/debug/apei/einj/error_type - done
>   # # 0x2 > /sys/kernel/debug/apei/einj/flags - done
>   # # 0x42c1234bad > /sys/kernel/debug/apei/einj/param1 - done
>   # # 0xffffffffffffffff > /sys/kernel/debug/apei/einj/param2 - done
>   # # 0x1 > /sys/kernel/debug/apei/einj/notrigger - done
>   # # 0x1 > /sys/kernel/debug/apei/einj/error_inject - done
>   # # Memory UER EINJected
>   # # SIGBUS (7) received, dumping siginfo...
>   # # si_signo=7, si_errno=0, si_code=128, si_addr=(nil)
>   # not ok 1 Exit with signal unhandled
>   ok 1 selftests: kvm: sea_to_user
>   # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> Changes since v1:
>   - New patch 1: drive EINJ injection directly through debugfs with
>     open()/write() instead of access()+popen(). Classify the open()
>     errno so an unprivileged run skips as "requires root" instead of
>     falsely reporting missing firmware EINJ, and report a genuine write
>     failure instead of the ambiguous "Failed... Success (0)".
>   - New patch 3: detect when notrigger=1 leaves no consumable poison and
>     skip cleanly, instead of exiting with a confusing KVM_EXIT_MMIO.
>   - Patch 2 is the original v1 change, unchanged.
>
> Not yet addressed from [2]: dropping the hard 1GB-hugepage and 4kB
> base-page requirements. Suggestions on an acceptable backing scheme are
> welcome.
>
> [1] https://lore.kernel.org/kvm/20260817080759.25601-1-likexu@xxxxxxxxxxx/
> [2] https://lore.kernel.org/all/86y0le9cvz.wl-maz@xxxxxxxxxx/
>
> Like Xu (3):
>   KVM: selftests: arm64: Fix EINJ handling in sea_to_user
>   KVM: selftests: arm64: Skip sea_to_user without 1GB hugepages
>   KVM: selftests: arm64: Skip sea_to_user when EINJ places no poison
>
>  .../testing/selftests/kvm/arm64/sea_to_user.c | 75 +++++++++++++++----
>  .../testing/selftests/kvm/include/test_util.h |  1 +
>  tools/testing/selftests/kvm/lib/test_util.c   | 15 ++++
>  3 files changed, 77 insertions(+), 14 deletions(-)
>
> --
> 2.50.1 (Apple Git-155)
>