RISC-V: KVM: Introduce ISA extension register

Currently, there is no provision for vmm (qemu-kvm or kvmtool) to
query about multiple-letter ISA extensions. The config register
is only used for base single letter ISA extensions.

A new ISA extension register is added that will allow the vmm
to query about any ISA extension one at a time. It is enabled for
both single letter or multi-letter ISA extensions. The ISA extension
register is useful to if the vmm requires to retrieve/set single
extension while the config register should be used if all the base
ISA extension required to retrieve or set.

For any multi-letter ISA extensions, the new register interface
must be used.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>

diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
index f808ad1..6119368 100644 (file)
--- a/arch/riscv/include/uapi/asm/kvm.h
+++ b/arch/riscv/include/uapi/asm/kvm.h
@@ -82,6 +82,23 @@ struct kvm_riscv_timer {
        __u64 state;
 };
 
+/*
+ * ISA extension IDs specific to KVM. This is not the same as the host ISA
+ * extension IDs as that is internal to the host and should not be exposed
+ * to the guest. This should always be contiguous to keep the mapping simple
+ * in KVM implementation.
+ */
+enum KVM_RISCV_ISA_EXT_ID {
+       KVM_RISCV_ISA_EXT_A = 0,
+       KVM_RISCV_ISA_EXT_C,
+       KVM_RISCV_ISA_EXT_D,
+       KVM_RISCV_ISA_EXT_F,
+       KVM_RISCV_ISA_EXT_H,
+       KVM_RISCV_ISA_EXT_I,
+       KVM_RISCV_ISA_EXT_M,
+       KVM_RISCV_ISA_EXT_MAX,
+};
+
 /* Possible states for kvm_riscv_timer */
 #define KVM_RISCV_TIMER_STATE_OFF      0
 #define KVM_RISCV_TIMER_STATE_ON       1
@@ -123,6 +140,9 @@ struct kvm_riscv_timer {
 #define KVM_REG_RISCV_FP_D_REG(name)   \
                (offsetof(struct __riscv_d_ext_state, name) / sizeof(__u64))
 
+/* ISA Extension registers are mapped as type 7 */
+#define KVM_REG_RISCV_ISA_EXT          (0x07 << KVM_REG_RISCV_TYPE_SHIFT)
+
 #endif
 
 #endif /* __LINUX_KVM_RISCV_H */

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index a7c8400..7f4ad5e 100644 (file)
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -374,6 +374,101 @@ static int kvm_riscv_vcpu_set_reg_csr(struct kvm_vcpu *vcpu,
        return 0;
 }
 
+/* Mapping between KVM ISA Extension ID & Host ISA extension ID */
+static unsigned long kvm_isa_ext_arr[] = {
+       RISCV_ISA_EXT_a,
+       RISCV_ISA_EXT_c,
+       RISCV_ISA_EXT_d,
+       RISCV_ISA_EXT_f,
+       RISCV_ISA_EXT_h,
+       RISCV_ISA_EXT_i,
+       RISCV_ISA_EXT_m,
+};
+
+static int kvm_riscv_vcpu_get_reg_isa_ext(struct kvm_vcpu *vcpu,
+                                         const struct kvm_one_reg *reg)
+{
+       unsigned long __user *uaddr =
+                       (unsigned long __user *)(unsigned long)reg->addr;
+       unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
+                                           KVM_REG_SIZE_MASK |
+                                           KVM_REG_RISCV_ISA_EXT);
+       unsigned long reg_val = 0;
+       unsigned long host_isa_ext;
+
+       if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
+               return -EINVAL;
+
+       if (reg_num >= KVM_RISCV_ISA_EXT_MAX || reg_num >= ARRAY_SIZE(kvm_isa_ext_arr))
+               return -EINVAL;
+
+       host_isa_ext = kvm_isa_ext_arr[reg_num];
+       if (__riscv_isa_extension_available(&vcpu->arch.isa, host_isa_ext))
+               reg_val = 1; /* Mark the given extension as available */
+
+       if (copy_to_user(uaddr, &reg_val, KVM_REG_SIZE(reg->id)))
+               return -EFAULT;
+
+       return 0;
+}
+
+static int kvm_riscv_vcpu_set_reg_isa_ext(struct kvm_vcpu *vcpu,
+                                         const struct kvm_one_reg *reg)
+{
+       unsigned long __user *uaddr =
+                       (unsigned long __user *)(unsigned long)reg->addr;
+       unsigned long reg_num = reg->id & ~(KVM_REG_ARCH_MASK |
+                                           KVM_REG_SIZE_MASK |
+                                           KVM_REG_RISCV_ISA_EXT);
+       unsigned long reg_val;
+       unsigned long host_isa_ext;
+       unsigned long host_isa_ext_mask;
+
+       if (KVM_REG_SIZE(reg->id) != sizeof(unsigned long))
+               return -EINVAL;
+
+       if (reg_num >= KVM_RISCV_ISA_EXT_MAX || reg_num >= ARRAY_SIZE(kvm_isa_ext_arr))
+               return -EINVAL;
+
+       if (copy_from_user(&reg_val, uaddr, KVM_REG_SIZE(reg->id)))
+               return -EFAULT;
+
+       host_isa_ext = kvm_isa_ext_arr[reg_num];
+       if (!__riscv_isa_extension_available(NULL, host_isa_ext))
+               return  -EOPNOTSUPP;
+
+       if (host_isa_ext >= RISCV_ISA_EXT_BASE &&
+           host_isa_ext < RISCV_ISA_EXT_MAX) {
+               /*
+                * Multi-letter ISA extension. Currently there is no provision
+                * to enable/disable the multi-letter ISA extensions for guests.
+                * Return success if the request is to enable any ISA extension
+                * that is available in the hardware.
+                * Return -EOPNOTSUPP otherwise.
+                */
+               if (!reg_val)
+                       return -EOPNOTSUPP;
+               else
+                       return 0;
+       }
+
+       /* Single letter base ISA extension */
+       if (!vcpu->arch.ran_atleast_once) {
+               host_isa_ext_mask = BIT_MASK(host_isa_ext);
+               if (!reg_val && (host_isa_ext_mask & KVM_RISCV_ISA_DISABLE_ALLOWED))
+                       vcpu->arch.isa &= ~host_isa_ext_mask;
+               else
+                       vcpu->arch.isa |= host_isa_ext_mask;
+               vcpu->arch.isa &= riscv_isa_extension_base(NULL);
+               vcpu->arch.isa &= KVM_RISCV_ISA_ALLOWED;
+               kvm_riscv_vcpu_fp_reset(vcpu);
+       } else {
+               return -EOPNOTSUPP;
+       }
+
+       return 0;
+}
+
 static int kvm_riscv_vcpu_set_reg(struct kvm_vcpu *vcpu,
                                  const struct kvm_one_reg *reg)
 {
@@ -391,6 +486,8 @@ static int kvm_riscv_vcpu_set_reg(struct kvm_vcpu *vcpu,
        else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_FP_D)
                return kvm_riscv_vcpu_set_reg_fp(vcpu, reg,
                                                 KVM_REG_RISCV_FP_D);
+       else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_ISA_EXT)
+               return kvm_riscv_vcpu_set_reg_isa_ext(vcpu, reg);
 
        return -EINVAL;
 }
@@ -412,6 +509,8 @@ static int kvm_riscv_vcpu_get_reg(struct kvm_vcpu *vcpu,
        else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_FP_D)
                return kvm_riscv_vcpu_get_reg_fp(vcpu, reg,
                                                 KVM_REG_RISCV_FP_D);
+       else if ((reg->id & KVM_REG_RISCV_TYPE_MASK) == KVM_REG_RISCV_ISA_EXT)
+               return kvm_riscv_vcpu_get_reg_isa_ext(vcpu, reg);
 
        return -EINVAL;
 }