RISC-V: KVM: provide UAPI for host SATP mode

KVM userspaces need to be aware of the host SATP to allow them to
advertise it back to the guest OS.

Since this information is used to build the guest FDT we can't wait for
the SATP reg to be readable. We just need to read the SATP mode, thus
we can use the existing 'satp_mode' global that represents the SATP reg
with MODE set and both ASID and PPN cleared. E.g. for a 32 bit host
running with sv32 satp_mode is 0x80000000, for a 64 bit host running
sv57 satp_mode is 0xa000000000000000, and so on.

Add a new userspace virtual config register 'satp_mode' to allow
userspace to read the current SATP mode the host is using with
GET_ONE_REG API before spinning the vcpu.

'satp_mode' can't be changed via KVM, so SET_ONE_REG is allowed as long
as userspace writes the existing 'satp_mode'.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 7bac43a3176ed1d45aad779e2e625e0dfa17ecd5..777cb8299551ca3a33147471f032d319cdbcfb35 100644 (file)
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -54,6 +54,7 @@
 #ifndef CONFIG_64BIT
 #define SATP_PPN       _AC(0x003FFFFF, UL)
 #define SATP_MODE_32   _AC(0x80000000, UL)
+#define SATP_MODE_SHIFT        31
 #define SATP_ASID_BITS 9
 #define SATP_ASID_SHIFT        22
 #define SATP_ASID_MASK _AC(0x1FF, UL)
@@ -62,6 +63,7 @@
 #define SATP_MODE_39   _AC(0x8000000000000000, UL)
 #define SATP_MODE_48   _AC(0x9000000000000000, UL)
 #define SATP_MODE_57   _AC(0xa000000000000000, UL)
+#define SATP_MODE_SHIFT        60
 #define SATP_ASID_BITS 16
 #define SATP_ASID_SHIFT        44
 #define SATP_ASID_MASK _AC(0xFFFF, UL)

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index 9c35e1427f7337eec64d5a0f7ee66c82ae04ec9f..992c5e407104958532d7ba930d50447ebe56fa25 100644 (file)
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -55,6 +55,7 @@ struct kvm_riscv_config {
        unsigned long marchid;
        unsigned long mimpid;
        unsigned long zicboz_block_size;
+       unsigned long satp_mode;
 };
 
 /* CORE registers for KVM_GET_ONE_REG and KVM_SET_ONE_REG */

diff --git a/arch/riscv/kvm/vcpu_onereg.c b/arch/riscv/kvm/vcpu_onereg.c
index 0dc2c2cecb450ba7c90de29ee2ec0f1ede035c99..85773e858120f8049630d1e4b92b95f08a2e4c89 100644 (file)
--- a/arch/riscv/kvm/vcpu_onereg.c
+++ b/arch/riscv/kvm/vcpu_onereg.c
@@ -152,6 +152,9 @@ static int kvm_riscv_vcpu_get_reg_config(struct kvm_vcpu *vcpu,
        case KVM_REG_RISCV_CONFIG_REG(mimpid):
                reg_val = vcpu->arch.mimpid;
                break;
+       case KVM_REG_RISCV_CONFIG_REG(satp_mode):
+               reg_val = satp_mode >> SATP_MODE_SHIFT;
+               break;
        default:
                return -EINVAL;
        }
@@ -234,6 +237,10 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
                else
                        return -EBUSY;
                break;
+       case KVM_REG_RISCV_CONFIG_REG(satp_mode):
+               if (reg_val != (satp_mode >> SATP_MODE_SHIFT))
+                       return -EINVAL;
+               break;
        default:
                return -EINVAL;
        }