[PATCH v3 0/2] Support runtime configuration for per-VM's HGATP mode

[fangyu.yu@linux.alibaba.com]

From: Fangyu Yu <fangyu.yu@linux.alibaba.com>

Currently, RISC-V KVM hardcodes the G-stage page table format (HGATP mode)
to the maximum mode detected at boot time (e.g., SV57x4 if supported). but
often such a wide GPA is unnecessary, just as a host sometimes doesn't need
sv57.

This patch introduces per-VM configurability of the G-stage mode via a new
KVM capability: KVM_CAP_RISCV_SET_HGATP_MODE. User-space can now explicitly
request a specific HGATP mode (SV39x4, SV48x4, or SV57x4 on 64-bit) during
VM creation.

---
Changes in v3:
    - Reworked the patch formatting (per Drew).
    - Dropped kvm->arch.kvm_riscv_gstage_mode and derive HGATP.MODE from
      kvm_riscv_gstage_pgd_levels via a helper, avoiding redundant per-VM state(per Drew).
    - Removed kvm_riscv_gstage_max_mode and keep only kvm_riscv_gstage_max_pgd_levels
      for host capability detection(per Drew).
    - Other initialization and return value issues(per Drew).
    - Enforce that KVM_CAP_RISCV_SET_HGATP_MODE can only be enabled before any vCPUs
      are created by rejecting the ioctl once kvm->created_vcpus is non-zero(per Radim).
    - Add a memslot safety check and reject the capability unless
      kvm_are_all_memslots_empty(kvm) is true, ensuring the G-stage format is not
      changed after any memslots have been installed(per Radim).
    - Link to v2:
      https://lore.kernel.org/linux-riscv/20260105143232.76715-1-fangyu.yu@linux.alibaba.com/
---

Fangyu Yu (2):
  RISC-V: KVM: Support runtime configuration for per-VM's HGATP mode
  RISC-V: KVM: add KVM_CAP_RISCV_SET_HGATP_MODE

 Documentation/virt/kvm/api.rst      | 18 +++++++
 arch/riscv/include/asm/kvm_gstage.h | 11 ++---
 arch/riscv/include/asm/kvm_host.h   | 19 +++++++
 arch/riscv/kvm/gstage.c             | 77 ++++++++++++++++-------------
 arch/riscv/kvm/main.c               | 12 ++---
 arch/riscv/kvm/mmu.c                | 23 ++++++---
 arch/riscv/kvm/vm.c                 | 28 +++++++++--
 arch/riscv/kvm/vmid.c               |  3 +-
 include/uapi/linux/kvm.h            |  1 +
 9 files changed, 133 insertions(+), 59 deletions(-)

-- 
2.50.1


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