Messages in this thread Patch in this message |  | | From | fangyu.yu@linux ... | | Subject | [PATCH v8 3/3] RISC-V: KVM: Reuse KVM_CAP_VM_GPA_BITS to select HGATP.MODE | | Date | Fri, 3 Apr 2026 23:30:18 +0800 |
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From: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Reuse KVM_CAP_VM_GPA_BITS to advertise and select the effective G-stage GPA width for a VM.
KVM_CHECK_EXTENSION(KVM_CAP_VM_GPA_BITS) returns the effective GPA bits for a VM, KVM_ENABLE_CAP(KVM_CAP_VM_GPA_BITS) allows userspace to downsize the effective GPA width by selecting a smaller G-stage page table format: - gpa_bits <= 41 selects Sv39x4 (pgd_levels=3) - gpa_bits <= 50 selects Sv48x4 (pgd_levels=4) - gpa_bits <= 59 selects Sv57x4 (pgd_levels=5)
Reject the request with -EINVAL for unsupported values and with -EBUSY if vCPUs have been created or any memslot is populated.
Signed-off-by: Fangyu Yu <fangyu.yu@linux.alibaba.com> Reviewed-by: Andrew Jones <andrew.jones@oss.qualcomm.com> Reviewed-by: Guo Ren <guoren@kernel.org> --- arch/riscv/kvm/vm.c | 44 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 42 insertions(+), 2 deletions(-)
diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c index fb7c4e07961f..a9f083feeb76 100644 --- a/arch/riscv/kvm/vm.c +++ b/arch/riscv/kvm/vm.c @@ -214,12 +214,52 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) { + if (cap->flags) + return -EINVAL; + switch (cap->cap) { case KVM_CAP_RISCV_MP_STATE_RESET: - if (cap->flags) - return -EINVAL; kvm->arch.mp_state_reset = true; return 0; + case KVM_CAP_VM_GPA_BITS: { + unsigned long gpa_bits = cap->args[0]; + unsigned long new_levels; + int r = 0; + + /* Decide target pgd levels from requested gpa_bits */ +#ifdef CONFIG_64BIT + if (gpa_bits <= 41) + new_levels = 3; /* Sv39x4 */ + else if (gpa_bits <= 50) + new_levels = 4; /* Sv48x4 */ + else if (gpa_bits <= 59) + new_levels = 5; /* Sv57x4 */ + else + return -EINVAL; +#else + /* 32-bit: only Sv32x4*/ + if (gpa_bits <= 34) + new_levels = 2; + else + return -EINVAL; +#endif + if (new_levels > kvm_riscv_gstage_max_pgd_levels) + return -EINVAL; + + /* Follow KVM's lock ordering: kvm->lock -> kvm->slots_lock. */ + mutex_lock(&kvm->lock); + mutex_lock(&kvm->slots_lock); + + if (kvm->created_vcpus || !kvm_are_all_memslots_empty(kvm)) + r = -EBUSY; + else + kvm->arch.pgd_levels = new_levels; + + mutex_unlock(&kvm->slots_lock); + mutex_unlock(&kvm->lock); + + return r; + } default: return -EINVAL; } -- 2.50.1
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