[PATCH v1 00/17] [RISC-V] virtual interrupt controller (vAPLIC/vIMSIC) support

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

Hi all,

This series adds the initial virtual interrupt controller (vINTC) support
for RISC-V guests in Xen, based on the Advanced Interrupt Architecture
(AIA): a virtual APLIC (vAPLIC) in MSI mode backed by a virtual IMSIC
(vIMSIC) using hardware guest interrupt files.

Rather than emulating APLIC in direct-delivery mode (which requires
trap-and-emulate for every interrupt and is costly), the series targets
IMSIC from the start. AIA lets a hart implement several "guest interrupt
files" (up to GEILEN), so external interrupts can be delivered to a vCPU
directly by hardware via the VGEIN field of hstatus, without a hypervisor
round-trip. Xen only has to emulate the APLIC MMIO programming interface
and route the guest's intent onto the physical MSI topology; interrupt
delivery itself stays in hardware.

The work breaks down into a few logical blocks:

Physical APLIC/AIA groundwork (patches 1-3)
  - Correctly track IRQ_DISABLED across runtime enable/disable and order
    the ->status update against the IMSIC CSR write.
  - Per-pCPU VGEIN (guest interrupt file) allocator: assign/release a
    hardware guest file to a vCPU and program hstatus.VGEIN.
  - Add the missing APLIC register offsets/masks needed by both the
    physical and virtual APLIC code (no functional change).

Device-agnostic MMIO dispatch + vAPLIC emulation (patches 4-5)
  - A per-domain MMIO handler table modelled on Arm's framework, so
    emulated devices self-register their GPA ranges and the fault path
    stays agnostic via a single try_handle_mmio() entry point.
  - vAPLIC MMIO read/write emulation. Writes are gated by the domain's
    authorised-IRQ bitmap so a guest cannot touch interrupts it does not
    own, and TARGET writes are translated from virtual to physical
    hart/guest-file indices. Delegation (SOURCECFG.D) is not yet
    supported.

vIMSIC guest interrupt files and state (patches 6-9)
  - Stage-2 map a vCPU's physical guest interrupt file to the fixed
    per-vCPU GPA page the guest expects at offset 0.
  - vcpu_aia_init(): assign a VGEIN, map its guest file and record the
    IMSIC state as a consistent unit.
  - IMSIC state save/restore (currently tracking which pCPU owns the
    guest file, needed because the pCPU id is part of the MSI address).
  - has_msi_support() helper to decide whether IMSIC state has to be
    saved/restored.

vINTC state save/restore plumbing (patches 10-11)
  - vintc_state_{save,restore}() wrappers over new store/restore hooks in
    struct vintc_ops, and the vAPLIC implementation of those hooks. No
    callers are wired up yet; the context-switch calls arrive with vCPU
    context switch support.

Trap and instruction emulation infrastructure (patches 12-17)
  - Extend the exception-table format with type/data fields and add
    EX_TYPE_TRAP_INFO so fixups can capture sepc/scause/stval.
  - riscv_vcpu_unpriv_read() (HLV/HLVX) to read guest memory/instructions
    safely, and riscv_vcpu_trap_redirect() to forward a synchronous trap
    back into the guest's VS-mode handler.
  - A guest page-fault handler that decodes the trapped load/store
    instruction (HTINST, or an unprivileged fetch as a fallback) and
    dispatches the MMIO access through try_handle_mmio().

Note on versioning: the series is posted as v1 as a freshly split-out
series, but several patches carry v2/v3 changelogs because they were
previously circulated as part of a larger another patches [1] from which the
current depends.

CI tests: https://gitlab.com/xen-project/people/olkur/xen/-/pipelines/2690874319

[1] 
https://lore.kernel.org/xen-devel/cover.1784559209.git.oleksii.kurochko@xxxxxxxxx/T/#t

Oleksii Kurochko (17):
  xen/riscv: manage IRQ_DISABLED flag in APLIC irq enable/disable
    callbacks
  xen/riscv: add basic VGEIN management for AIA guests
  xen/riscv: add missing APLIC register offsets, masks to asm/aplic.h
  xen/riscv: introduce device-agnostic MMIO emulation dispatch
  xen/riscv: implement virtual APLIC MMIO emulation
  xen/riscv: map IMSIC interrupt file for vCPUs
  xen/riscv: introduce vCPU AIA initialization
  xen/riscv: add IMSIC state save/restore
  xen/riscv: add helper to check APLIC MSI mode
  xen/riscv: introduce vintc_state_{save,restore}()
  xen/riscv: add vAPLIC state save/restore hooks
  xen/riscv: extend exception tables with type and data fields
  xen/riscv: add unprivileged guest memory read helper
  xen/riscv: add guest page fault handling stub
  xen/riscv: implement trap redirection to a guest
  xen/riscv: add guest load emulation for trapped MMIO accesses
  xen/riscv: add guest store emulation for trapped MMIO accesses

 xen/arch/riscv/Makefile                   |   1 +
 xen/arch/riscv/aia.c                      | 175 ++++++++++++
 xen/arch/riscv/aplic-priv.h               |   2 +
 xen/arch/riscv/aplic.c                    |  83 +++++-
 xen/arch/riscv/domain.c                   |   4 +
 xen/arch/riscv/extable.c                  |  60 +++-
 xen/arch/riscv/guestcopy.c                | 145 ++++++++++
 xen/arch/riscv/imsic.c                    |  99 +++++++
 xen/arch/riscv/include/asm/aia.h          |  10 +
 xen/arch/riscv/include/asm/aplic.h        |  61 +++++
 xen/arch/riscv/include/asm/domain.h       |   3 +
 xen/arch/riscv/include/asm/extable.h      |  62 +++--
 xen/arch/riscv/include/asm/gpr-num.h      |  33 +++
 xen/arch/riscv/include/asm/guest_access.h |   8 +
 xen/arch/riscv/include/asm/imsic.h        |  17 ++
 xen/arch/riscv/include/asm/intc.h         |   9 +
 xen/arch/riscv/include/asm/mmio.h         |  63 +++++
 xen/arch/riscv/include/asm/processor.h    |   2 +
 xen/arch/riscv/include/asm/traps.h        |  12 +
 xen/arch/riscv/include/asm/vaplic.h       |   6 +
 xen/arch/riscv/intc.c                     |  14 +
 xen/arch/riscv/mmio.c                     | 145 ++++++++++
 xen/arch/riscv/traps.c                    | 279 +++++++++++++++++++
 xen/arch/riscv/vaplic.c                   | 319 ++++++++++++++++++++++
 24 files changed, 1590 insertions(+), 22 deletions(-)
 create mode 100644 xen/arch/riscv/include/asm/gpr-num.h
 create mode 100644 xen/arch/riscv/include/asm/mmio.h
 create mode 100644 xen/arch/riscv/mmio.c

-- 
2.54.0