Message-Id: <20260204134507.33912-1-fangyu.yu@linux.alibaba.com>
Date: Wed,  4 Feb 2026 21:45:04 +0800
From: fangyu.yu@...ux.alibaba.com
To: pbonzini@...hat.com,
	corbet@....net,
	anup@...infault.org,
	atish.patra@...ux.dev,
	pjw@...nel.org,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alex@...ti.fr
Cc: guoren@...nel.org,
	radim.krcmar@....qualcomm.com,
	andrew.jones@....qualcomm.com,
	linux-doc@...r.kernel.org,
	kvm@...r.kernel.org,
	kvm-riscv@...ts.infradead.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Fangyu Yu <fangyu.yu@...ux.alibaba.com>
Subject: [PATCH v5 0/3] Support runtime configuration for per-VM's HGATP mode

From: Fangyu Yu <fangyu.yu@...ux.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, SV57x4 or SV32x4) during
VM creation.

---
Changes in v5:
    - Use architectural HGATP.MODE encodings as the bit index for the supported-mode
      bitmap and for the VM-mode selection UAPI; no new UAPI mode/bit defines are
      introduced(per Radim).
    - Allow KVM_CAP_RISCV_SET_HGATP_MODE on RV32 as well(per Drew).
    - Link to v4:
      https://lore.kernel.org/linux-riscv/20260202140716.34323-1-fangyu.yu@linux.alibaba.com/
---
Changes in v4:
    - Extend kvm_riscv_gstage_mode_detect() to probe all HGATP.MODE values
      supported by the host and record them in a bitmask.
    - Treat unexpected pgd_levels in kvm_riscv_gstage_mode() as an internal error
      (e.g. WARN_ON_ONCE())(per Radim).
    - Move kvm_riscv_gstage_gpa_bits() and kvm_riscv_gstage_gpa_size() to header
      as static inline helpers(per Radim).
    - Drop gstage_mode_user_initialized and Remove the kvm_debug() message from
      KVM_CAP_RISCV_SET_HGATP_MODE(per Radim).
    - Link to v3:
      https://lore.kernel.org/linux-riscv/20260125150450.27068-1-fangyu.yu@linux.alibaba.com/
---
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 (3):
  RISC-V: KVM: Support runtime configuration for per-VM's HGATP mode
  RISC-V: KVM: Detect and expose supported HGATP G-stage modes
  RISC-V: KVM: add KVM_CAP_RISCV_SET_HGATP_MODE

 Documentation/virt/kvm/api.rst      |  27 ++++++++
 arch/riscv/include/asm/kvm_gstage.h |  31 +++++++--
 arch/riscv/include/asm/kvm_host.h   |  19 ++++++
 arch/riscv/kvm/gstage.c             | 102 ++++++++++++++--------------
 arch/riscv/kvm/main.c               |  12 ++--
 arch/riscv/kvm/mmu.c                |  20 +++---
 arch/riscv/kvm/vm.c                 |  21 +++++-
 arch/riscv/kvm/vmid.c               |   3 +-
 include/uapi/linux/kvm.h            |   1 +
 9 files changed, 160 insertions(+), 76 deletions(-)

-- 
2.50.1

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