Messages in this thread |  | | From | fangyu.yu@linux ... | | Subject | [PATCH v8 0/3] Support runtime configuration for per-VM's HGATP mode | | Date | Fri, 3 Apr 2026 23:30:15 +0800 |
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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 reuse KVM_CAP_VM_GPA_BITS to select HGATP.MODE. User-space can now explicitly request a specific HGATP mode (SV39x4, SV48x4, SV57x4 or SV32x4) during VM creation.
--- Changes in v8: - Reuse KVM_CAP_VM_GPA_BITS to advertise and select the effective GPA width for a VM (Anup's suggestion). - Handle the kvm == NULL case and task kvm->lock and kvm->slots_lock to serialize against concurrent vCPU creation and memslot updates (Radim's suggestion). - Link to v7: https://lore.kernel.org/linux-riscv/20260402132303.6252-1-fangyu.yu@linux.alibaba.com/ --- Changes in v7 (Anup's suggestions): - Keep the original HGATP mode probing logic. - Link to v6: https://lore.kernel.org/linux-riscv/20260330122601.22140-1-fangyu.yu@linux.alibaba.com/ --- Changes in v6 (Anup's suggestions): - Reworked kvm_riscv_gstage_gpa_bits() and kvm_riscv_gstage_gpa_size() to take "unsigned long pgd_levels" instead of "struct kvm_arch *". - Moved kvm_riscv_gstage_mode() helper from kvm_host.h to kvm_gstage.h. - Renamed kvm->arch.kvm_riscv_gstage_pgd_levels to kvm->arch.pgd_levels. - Added pgd_levels to struct kvm_gstage to avoid repeated gstage->kvm->arch pointer chasing. - Link to v5: https://lore.kernel.org/linux-riscv/20260204134507.33912-1-fangyu.yu@linux.alibaba.com/ --- 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: Cache gstage pgd_levels in struct kvm_gstage RISC-V: KVM: Reuse KVM_CAP_VM_GPA_BITS to select HGATP.MODE
arch/riscv/include/asm/kvm_gstage.h | 47 ++++++++++++++++--- arch/riscv/include/asm/kvm_host.h | 1 + arch/riscv/kvm/gstage.c | 65 +++++++++++++-------------- arch/riscv/kvm/main.c | 12 ++--- arch/riscv/kvm/mmu.c | 70 +++++++++-------------------- arch/riscv/kvm/vm.c | 49 ++++++++++++++++++-- arch/riscv/kvm/vmid.c | 3 +- 7 files changed, 148 insertions(+), 99 deletions(-)
-- 2.50.1
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