[PATCH v3 0/3] Add support for Supervisor Software Events extension

[Anup Patel]

On Fri, Apr 5, 2024 at 10:28 PM Samuel Holland
<samuel.holland at sifive.com> wrote:
>
> Hi Anup,
>
> On 2024-04-05 6:46 AM, Anup Patel wrote:
> > On Thu, Mar 21, 2024 at 9:27 PM Clément Léger <cleger at rivosinc.com> wrote:
> >>
> >> The SBI Supervisor Software Events (SSE) extensions provides a mechanism
> >> to inject software events from an SBI implementation to supervisor
> >> software such that it preempts all other supervisor level traps and
> >> interrupts [1]. This series implements the V3 version of the spec.
> >>
> >> Various events are defined and can be send asynchronously to supervisor
> >> software (RAS, PMU, DEBUG, Asynchronous page fault) from SBI as well
> >> as platform specific events. Events can be either local (per-hart) or
> >> global. Events can be nested on top of each other based on priority and
> >> can interrupt the supervisor mode at any time.
> >>
> >> This implementation can be tested using kvm-unit-tests [2] with the
> >> following commands:
> >>
> >> Build kvm-unit-tests:
> >>
> >> $ git clone https://github.com/clementleger/kvm-unit-tests.git
> >> $ cd kvm-unit-tests
> >> $ git switch dev/cleger/sse
> >> $ ./configure --arch=riscv64 --cross-prefix=$CROSS_COMPILE
> >> $ make
> >>
> >> Run using Qemu:
> >>
> >> $ ./qemu-system-riscv64 \
> >>         -smp 4 \
> >>         -M virt \
> >>         -cpu rv64 \
> >>         -nographic \
> >>         -serial mon:stdio \
> >>         -bios <opensbi>/build/platform/generic/firmware/fw_jump.bin \
> >>         -kernel <kvm-unit-tests>/riscv/sbi_sse.flat
> >>
> >> An implementation of a SSE "client" in linux is available [3].
> >> This series can be found on github [5].
> >>
> >> Link: https://lists.riscv.org/g/tech-prs/message/798 [1]
> >> Link: https://github.com/clementleger/kvm-unit-tests/tree/dev/cleger/sse [2]
> >> Link: https://github.com/rivosinc/linux/tree/dev/cleger/sse [3]
> >> Link: http://lists.infradead.org/pipermail/opensbi/2024-March/006670.html [4]
> >> Link: https://github.com/rivosinc/opensbi/tree/dev/cleger/sse_v3 [5]
> >>
> >> ---
> >>
> >> Changes from v3:
> >>  - Changes to follow v3 SSE specification
> >>  - Use masks instead of struct with bitfields for status
> >>  - Rework locking
> >>  - SSE pending event processing is now done upon returning to previous
> >>    mode
> >>
> >> v2: http://lists.infradead.org/pipermail/opensbi/2024-January/006223.html
> >>
> >> Changes from v2:
> >>  - Move local/global event count initialization out of sse_global_init()
> >>  - Remove PMU_IRQ_CLEAR SBI call and clear IRQ on SSE event completion
> >>  - Change SBI_ERR_X to SBI_EXX defines
> >>  - Add guards for invalid __riscv_xlen values
> >>  - Update parameters passing (a6, a7)
> >>
> >> v1: http://lists.infradead.org/pipermail/opensbi/2023-November/006015.html
> >>
> >> Changes from v1:
> >>  - Implemented SSE Spec v2
> >>  - Change event state checking (Xiang W)
> >>
> >> Clément Léger (3):
> >>   lib: sbi: Add support for Supervisor Software Events extension
> >>   lib: sbi: Implement SBI SSE extension
> >>   lib: sbi: Add SSE support for PMU events
> >
> > Reviewed-by: Anup Patel <anup at brainfault.org>
> >
> > Applied this series to the riscv/opensbi repo.
>
> I don't think this series is ready to apply yet, considering that the extension
> specification has not even been merged. Or is the master branch not expected to
> be forward-compatible with the SBI spec?

In OpenSBI, we treat SBI extensions in draft state as experimental. The
Linux kernel anyway does not accept patches for draft specifications so
keeping it experiential in OpenSBI is fine.

Further, we only increment the advertised SBI spec version in OpenSBI
after the SBI spec is frozen.

This approach has helped us make progress on other dependent work.
For example, RAS efforts in OpenSBI depend heavily on the SBI SSE
series (this series).

Regards,
Anup

>
> Regards,
> Samuel
>
> > Thanks,
> > Anup
> >
> >>
> >>  include/sbi/sbi_ecall_interface.h |   79 +-
> >>  include/sbi/sbi_error.h           |    2 +
> >>  include/sbi/sbi_pmu.h             |    3 +
> >>  include/sbi/sbi_sse.h             |   94 +++
> >>  lib/sbi/Kconfig                   |    4 +
> >>  lib/sbi/objects.mk                |    4 +
> >>  lib/sbi/sbi_ecall_sse.c           |   57 ++
> >>  lib/sbi/sbi_init.c                |   13 +
> >>  lib/sbi/sbi_pmu.c                 |   51 ++
> >>  lib/sbi/sbi_sse.c                 | 1131 +++++++++++++++++++++++++++++
> >>  lib/sbi/sbi_trap.c                |   11 +
> >>  11 files changed, 1448 insertions(+), 1 deletion(-)
> >>  create mode 100644 include/sbi/sbi_sse.h
> >>  create mode 100644 lib/sbi/sbi_ecall_sse.c
> >>  create mode 100644 lib/sbi/sbi_sse.c
> >>
> >> --
> >> 2.43.0
> >>
> >>
> >> --
> >> opensbi mailing list
> >> opensbi at lists.infradead.org
> >> http://lists.infradead.org/mailman/listinfo/opensbi
> >
>