[PATCH RFC 3/3] lib: sbi: Add VIRQ ecall extension

[Raymond Mao]

Hi Andrew,

On Fri, Feb 13, 2026 at 4:03 PM Andrew Jones
<andrew.jones at oss.qualcomm.com> wrote:
>
> On Fri, Feb 13, 2026 at 02:04:59PM -0500, Raymond Mao wrote:
> > From: Raymond Mao <raymond.mao at riscstar.com>
> >
> > Add vendor SBI extension ecall for VIRQ.
> > This allows S-mode payload to pop/complete the next pending VIRQ has
> > couried into the current domain.
> >
> > Signed-off-by: Raymond Mao <raymond.mao at riscstar.com>
> > ---
> >  include/sbi/sbi_ecall_interface.h | 18 ++++++++++
> >  lib/sbi/Kconfig                   |  5 +++
> >  lib/sbi/objects.mk                |  3 ++
> >  lib/sbi/sbi_ecall_virq.c          | 57 +++++++++++++++++++++++++++++++
> >  4 files changed, 83 insertions(+)
> >  create mode 100644 lib/sbi/sbi_ecall_virq.c
> >
> > diff --git a/include/sbi/sbi_ecall_interface.h b/include/sbi/sbi_ecall_interface.h
> > index 76624e3f..9cb9a7eb 100644
> > --- a/include/sbi/sbi_ecall_interface.h
> > +++ b/include/sbi/sbi_ecall_interface.h
> > @@ -126,6 +126,24 @@
> >  #define SBI_EXT_FWFT_SET             0x0
> >  #define SBI_EXT_FWFT_GET             0x1
> >
> > +#ifdef CONFIG_SBI_ECALL_VIRQ
> > +
> > +/* Vendor extension base range is defined by the SBI spec. Choose a private ID. */
> > +#define SBI_EXT_VIRQ                 0x0900524d
>
> I'm not sure where this number comes from. I'd expect it to be
> 0x56495251 == "VIRQ"
>
> > +
> > +/* Function IDs for SBI_EXT_VIRQ */
> > +#define SBI_EXT_VIRQ_POP             0
> > +#define SBI_EXT_VIRQ_COMPLETE                1
> > +
> > +/*
> > + * SBI_EXT_VIRQ_POP
> > + * Returns:
> > + *   a0: SBI error code (0 for success)
> > + *   a1: next pending hwirq (0 if none pending)
>                          ^ virq, but...
>
> how about creating an SBI function which allows registering a shared
> memory region (as several SBI extensions already do) and then place a
> bitmap in that shared memory which represents all virqs (a set bit means
> that that virq is pending). That would allow S-mode to immediately get
> all pending virqs in its SSE handler and we wouldn't need to worry about
> a queue filling up. The downside is that S-mode wouldn't necessarily
> handle the virqs in FIFO order. But, that can be a feature, because the
> queue forces FIFO order whereas S-mode may need to handle them in some
> priority order instead.
>

This sounds good. Maybe we can make both implementations selectable
via Kconfigs.
Let me collect more feedback, I can make the optional bitmap in a second phase.

> > + */
> > +
> > +#endif
> > +
> >  enum sbi_fwft_feature_t {
> >       SBI_FWFT_MISALIGNED_EXC_DELEG           = 0x0,
> >       SBI_FWFT_LANDING_PAD                    = 0x1,
> > diff --git a/lib/sbi/Kconfig b/lib/sbi/Kconfig
> > index c6cc04bc..8479f861 100644
> > --- a/lib/sbi/Kconfig
> > +++ b/lib/sbi/Kconfig
> > @@ -69,4 +69,9 @@ config SBI_ECALL_SSE
> >  config SBI_ECALL_MPXY
> >       bool "MPXY extension"
> >       default y
> > +
> > +config SBI_ECALL_VIRQ
> > +     bool "VIRQ extension"
> > +     default y
> > +
> >  endmenu
> > diff --git a/lib/sbi/objects.mk b/lib/sbi/objects.mk
> > index 07d13229..18e590ab 100644
> > --- a/lib/sbi/objects.mk
> > +++ b/lib/sbi/objects.mk
> > @@ -64,6 +64,9 @@ libsbi-objs-$(CONFIG_SBI_ECALL_SSE) += sbi_ecall_sse.o
> >  carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_MPXY) += ecall_mpxy
> >  libsbi-objs-$(CONFIG_SBI_ECALL_MPXY) += sbi_ecall_mpxy.o
> >
> > +carray-sbi_ecall_exts-$(CONFIG_SBI_ECALL_VIRQ) += ecall_virq
> > +libsbi-objs-$(CONFIG_SBI_ECALL_VIRQ) += sbi_ecall_virq.o
> > +
> >  libsbi-objs-y += sbi_bitmap.o
> >  libsbi-objs-y += sbi_bitops.o
> >  libsbi-objs-y += sbi_console.o
> > diff --git a/lib/sbi/sbi_ecall_virq.c b/lib/sbi/sbi_ecall_virq.c
> > new file mode 100644
> > index 00000000..b192598e
> > --- /dev/null
> > +++ b/lib/sbi/sbi_ecall_virq.c
> > @@ -0,0 +1,57 @@
> > +/*
> > + * SPDX-License-Identifier: BSD-2-Clause
> > + *
> > + * Copyright (c) 2026 RISCstar Solutions.
> > + *
> > + * Author: Raymond Mao <raymond.mao at riscstar.com>
> > + */
> > +
> > +#include <sbi/sbi_console.h>
> > +#include <sbi/sbi_ecall.h>
> > +#include <sbi/sbi_ecall_interface.h>
> > +#include <sbi/sbi_error.h>
> > +#include <sbi/sbi_trap.h>
> > +#include <sbi/sbi_virq.h>
> > +
> > +static int sbi_ecall_virq_handler(unsigned long extid,
> > +                               unsigned long funcid,
> > +                               struct sbi_trap_regs *regs,
> > +                               struct sbi_ecall_return *out)
> > +{
> > +     (void)extid;
> > +
> > +     sbi_printf("[ECALL VIRQ] VIRQ ecall handler, funcid: %ld\n", funcid);
>
> You'll want to get rid of these print statements when posting without the
> RFC.
>

Sure. No worries. The formal patch will come together with the
complete VIRQ implementation and all verbose prints will be removed.

Thanks and regards,
Raymond

> Thanks,
> drew