RISC-V: KVM: Add VM capability to allow userspace get GPA bits

The number of GPA bits supported for a RISC-V Guest/VM is based on the
MMU mode used by the G-stage translation. The KVM RISC-V will detect and
use the best possible MMU mode for the G-stage in kvm_arch_init().

We add a generic VM capability KVM_CAP_VM_GPA_BITS which can be used by
the KVM userspace to get the number of GPA (guest physical address) bits
supported for a Guest/VM.

Signed-off-by: Anup Patel <anup.patel@wdc.com>
Reviewed-and-tested-by: Atish Patra <atishp@rivosinc.com>

diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
index 52e1988..99ef6a1 100644 (file)
--- a/arch/riscv/include/asm/kvm_host.h
+++ b/arch/riscv/include/asm/kvm_host.h
@@ -218,6 +218,7 @@ void kvm_riscv_stage2_free_pgd(struct kvm *kvm);
 void kvm_riscv_stage2_update_hgatp(struct kvm_vcpu *vcpu);
 void kvm_riscv_stage2_mode_detect(void);
 unsigned long kvm_riscv_stage2_mode(void);
+int kvm_riscv_stage2_gpa_bits(void);
 
 void kvm_riscv_stage2_vmid_detect(void);
 unsigned long kvm_riscv_stage2_vmid_bits(void);

diff --git a/arch/riscv/kvm/mmu.c b/arch/riscv/kvm/mmu.c
index 5f2736c..9af67db 100644 (file)
--- a/arch/riscv/kvm/mmu.c
+++ b/arch/riscv/kvm/mmu.c
@@ -769,3 +769,8 @@ unsigned long kvm_riscv_stage2_mode(void)
 {
        return stage2_mode >> HGATP_MODE_SHIFT;
 }
+
+int kvm_riscv_stage2_gpa_bits(void)
+{
+       return stage2_gpa_bits;
+}

diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c
index 7619691..c768f75 100644 (file)
--- a/arch/riscv/kvm/vm.c
+++ b/arch/riscv/kvm/vm.c
@@ -74,6 +74,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
        case KVM_CAP_NR_MEMSLOTS:
                r = KVM_USER_MEM_SLOTS;
                break;
+       case KVM_CAP_VM_GPA_BITS:
+               r = kvm_riscv_stage2_gpa_bits();
+               break;
        default:
                r = 0;
                break;

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 1daa452..469f05d 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1131,6 +1131,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
 #define KVM_CAP_ARM_MTE 205
 #define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
+#define KVM_CAP_VM_GPA_BITS 207
 
 #ifdef KVM_CAP_IRQ_ROUTING