Re: [kvm-unit-tests PATCH v3 00/11] GIC fixes and improvements

[Alexandru Elisei <alexandru.elisei@arm.com>]

Hi Drew,

Had a chat in private with Andre regarding his comments on patch #8 ("arm/arm64:
gic: Split check_acked() into two functions") [1]. He said that the patch looks ok
to him. The delay he mentioned was triggered by him when testing his GIC patches
[2] on top of master.

[1] https://www.spinics.net/lists/kvm/msg231390.html

[2] https://lists.cs.columbia.edu/pipermail/kvmarm/2019-November/037853.html

Thanks,

Alex

On 1/29/21 4:36 PM, Alexandru Elisei wrote:
> What started this series is Andre's SPI and group interrupts tests [1],
> which prompted me to attempt to rewrite check_acked() so it's more flexible
> and not so complicated to review. When I was doing that I noticed that the
> message passing pattern for accesses to the acked, bad_irq and bad_sender
> arrays didn't look quite right, and that turned into the first 7 patches of
> the series. Even though the diffs are relatively small, they are not
> trivial and the reviewer can skip them for the more palatable patches that
> follow. I would still appreciate someone having a look at the memory
> ordering fixes.
>
> Patch #8 ("Split check_acked() into two functions") is where check_acked()
> is reworked with an eye towards supporting different timeout values or
> silent reporting without adding too many arguments to check_acked().
>
> After changing the IPI tests, I turned my attention to the LPI tests, which
> followed the same memory synchronization patterns, but invented their own
> interrupt handler and testing functions. Instead of redoing the work that I
> did for the IPI tests, I decided to convert the LPI tests to use the same
> infrastructure.
>
> For v2, I ran tests on the following machines and didn't see any issues:
>
> - Ampere EMAG: all arm64 tests 10,000+ times (combined) under qemu and
>   kvmtool.
>
> - rockpro64: the arm GICv2 and GICv3 tests 10,000+ times under kvmtool (I
>   chose kvmtool because it's faster than qemu); the arm64 gic tests (GICv2
>   and GICv3) 5000+ times with qemu (didn't realize that ./run_tests.sh -g
>   gic doesn't include the its tests); the arm64 GICv2 and GICv3 and ITS
>   tests under kvmtool 13,000+ times.
>
> For v3, because the changes weren't too big, I ran ./run_tests.sh for arm
> and arm64 with qemu TCG on the my x86 machine; ran ./run_tests.sh for arm64
> on rockpro64; and ran all the gic tests for arm and arm64 under kvmtool on
> the rockpro64.
>
> Changes in v3:
>
> * Gathered Reviewed-by tags, thank you for the feedback!
>
> * Reworked patch #2 and renamed it to "lib: arm/arm64: gicv2: Document
>   existing barriers when sending IPIs". The necessary barriers were already in
>   place in writel/readl. Dropped the R-b tag.
>
> * Removed the GICv2 smp_rmb() barrier in #4 ("arm/arm64: gic: Remove unnecessary
>   synchronization with stats_reset") because of the rmb() already present in
>   readl() and reworded the commit message accordingly. Dropped the R-b tag.
>
> * Commented the extra delay in wait_for_interrupts() for patch #8
>   ("arm/arm64: gic: Split check_acked() into two functions").
>
> * Minor change to the commit message for #10 ("arm64: gic: its-trigger:
>   Don't trigger the LPI while it is pending") as per Andre's suggestion.
>
> * Dropped patch #11 ("lib: arm64: gic-v3-its: Add wmb() barrier before INT
>   command") because the wmb() was already present in __its_send_int() ->
>   its_send_single_command() -> its_post_commands() -> writeq().
>
> Changes in v2:
>
> * Gathered Reviewed-by tags, thank you for the feedback!
>
> * Modified code comments in #1 ("lib: arm/arm64: gicv3: Add missing barrier
>   when sending IPIs") as per review suggestions.
>
> * Moved the barrier() in gicv2_ipi_send_self() from #3 ("arm/arm64: gic:
>   Remove memory synchronization from ipi_clear_active_handler()") to #2
>   ("lib: arm/arm64: gicv2: Add missing barrier when sending IPIs").
>
> * Renamed #3, changed "[..] Remove memory synchronization [..]" to
>   "[..] Remove SMP synchronization [..]".
>
> * Moved the removal of smp_rmb() from check_spurious() from #5 ("arm/arm64:
>   gic: Use correct memory ordering for the IPI test") to patch #7
>   ("arm/arm64: gic: Wait for writes to acked or spurious to complete").
>
> * Fixed typos in #8 ("arm/arm64: gic: Split check_acked() into two
>   functions").
>
> * Patch #10 ("arm64: gic: its-trigger: Don't trigger the LPI while it is
>   pending") is new. It was added to fix an issue found in v1 [2].
>
> * Patch #11 ("lib: arm64: gic-v3-its: Add wmb() barrier before INT
>   command") is also new; it was split from #12 ("arm64: gic: Use IPI test
>   checking for the LPI tests") following review comments.
>
> * Removed the now redundant call to stats_reset() from its_prerequisites()
>   in #12 ("arm64: gic: Use IPI test checking for the LPI tests").
>
> [1] https://lists.cs.columbia.edu/pipermail/kvmarm/2019-November/037853.html
> [2] https://www.spinics.net/lists/kvm-arm/msg43628.html
>
> Alexandru Elisei (11):
>   lib: arm/arm64: gicv3: Add missing barrier when sending IPIs
>   lib: arm/arm64: gicv2: Document existing barriers when sending IPIs
>   arm/arm64: gic: Remove SMP synchronization from
>     ipi_clear_active_handler()
>   arm/arm64: gic: Remove unnecessary synchronization with stats_reset()
>   arm/arm64: gic: Use correct memory ordering for the IPI test
>   arm/arm64: gic: Check spurious and bad_sender in the active test
>   arm/arm64: gic: Wait for writes to acked or spurious to complete
>   arm/arm64: gic: Split check_acked() into two functions
>   arm/arm64: gic: Make check_acked() more generic
>   arm64: gic: its-trigger: Don't trigger the LPI while it is pending
>   arm64: gic: Use IPI test checking for the LPI tests
>
>  lib/arm/gic-v2.c |   6 +
>  lib/arm/gic-v3.c |   6 +
>  arm/gic.c        | 338 +++++++++++++++++++++++++----------------------
>  3 files changed, 190 insertions(+), 160 deletions(-)
>