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RISC-V: KVM: Reuse KVM_CAP_VM_GPA_BITS to select HGATP.MODE

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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>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20260403153019.9916-4-fangyu.yu@linux.alibaba.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Fangyu Yu 2026-04-03 23:30:18 +08:00 committed by Anup Patel
parent ec92248431
commit 7263b4fdb0
1 changed files with 42 additions and 2 deletions
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44
arch/riscv/kvm/vm.c
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@ -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;
}