@@ -64,6 +64,8 @@ struct kvm_vcpu_stat {
u64 wfi_exit_stat;
u64 mmio_exit_user;
u64 mmio_exit_kernel;
+ u64 csr_exit_user;
+ u64 csr_exit_kernel;
u64 exits;
};
@@ -209,6 +211,9 @@ struct kvm_vcpu_arch {
/* MMIO instruction details */
struct kvm_mmio_decode mmio_decode;
+ /* CSR instruction details */
+ struct kvm_csr_decode csr_decode;
+
/* SBI context */
struct kvm_sbi_context sbi_context;
@@ -18,6 +18,11 @@ struct kvm_mmio_decode {
int return_handled;
};
+struct kvm_csr_decode {
+ unsigned long insn;
+ int return_handled;
+};
+
/* Return values used by function emulating a particular instruction */
enum kvm_insn_return {
KVM_INSN_EXIT_TO_USER_SPACE = 0,
@@ -28,6 +33,7 @@ enum kvm_insn_return {
};
void kvm_riscv_vcpu_wfi(struct kvm_vcpu *vcpu);
+int kvm_riscv_vcpu_csr_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
int kvm_riscv_vcpu_virtual_insn(struct kvm_vcpu *vcpu, struct kvm_run *run,
struct kvm_cpu_trap *trap);
@@ -26,6 +26,8 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
STATS_DESC_COUNTER(VCPU, wfi_exit_stat),
STATS_DESC_COUNTER(VCPU, mmio_exit_user),
STATS_DESC_COUNTER(VCPU, mmio_exit_kernel),
+ STATS_DESC_COUNTER(VCPU, csr_exit_user),
+ STATS_DESC_COUNTER(VCPU, csr_exit_kernel),
STATS_DESC_COUNTER(VCPU, exits)
};
@@ -869,6 +871,15 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
}
}
+ /* Process CSR value returned from user-space */
+ if (run->exit_reason == KVM_EXIT_RISCV_CSR) {
+ ret = kvm_riscv_vcpu_csr_return(vcpu, vcpu->run);
+ if (ret) {
+ kvm_vcpu_srcu_read_unlock(vcpu);
+ return ret;
+ }
+ }
+
if (run->immediate_exit) {
kvm_vcpu_srcu_read_unlock(vcpu);
return -EINTR;
@@ -14,6 +14,19 @@
#define INSN_MASK_WFI 0xffffffff
#define INSN_MATCH_WFI 0x10500073
+#define INSN_MATCH_CSRRW 0x1073
+#define INSN_MASK_CSRRW 0x707f
+#define INSN_MATCH_CSRRS 0x2073
+#define INSN_MASK_CSRRS 0x707f
+#define INSN_MATCH_CSRRC 0x3073
+#define INSN_MASK_CSRRC 0x707f
+#define INSN_MATCH_CSRRWI 0x5073
+#define INSN_MASK_CSRRWI 0x707f
+#define INSN_MATCH_CSRRSI 0x6073
+#define INSN_MASK_CSRRSI 0x707f
+#define INSN_MATCH_CSRRCI 0x7073
+#define INSN_MASK_CSRRCI 0x707f
+
#define INSN_MATCH_LB 0x3
#define INSN_MASK_LB 0x707f
#define INSN_MATCH_LH 0x1003
@@ -71,6 +84,7 @@
#define SH_RS1 15
#define SH_RS2 20
#define SH_RS2C 2
+#define MASK_RX 0x1f
#define RV_X(x, s, n) (((x) >> (s)) & ((1 << (n)) - 1))
#define RVC_LW_IMM(x) ((RV_X(x, 6, 1) << 2) | \
@@ -189,7 +203,162 @@ static int wfi_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
return KVM_INSN_CONTINUE_NEXT_SEPC;
}
+struct csr_func {
+ unsigned int base;
+ unsigned int count;
+ /*
+ * Possible return values are as same as "func" callback in
+ * "struct insn_func".
+ */
+ int (*func)(struct kvm_vcpu *vcpu, unsigned int csr_num,
+ unsigned long *val, unsigned long new_val,
+ unsigned long wr_mask);
+};
+
+static const struct csr_func csr_funcs[] = { };
+
+/**
+ * kvm_riscv_vcpu_csr_return -- Handle CSR read/write after user space
+ * emulation or in-kernel emulation
+ *
+ * @vcpu: The VCPU pointer
+ * @run: The VCPU run struct containing the CSR data
+ *
+ * Returns > 0 upon failure and 0 upon success
+ */
+int kvm_riscv_vcpu_csr_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
+{
+ ulong insn;
+
+ if (vcpu->arch.csr_decode.return_handled)
+ return 0;
+ vcpu->arch.csr_decode.return_handled = 1;
+
+ /* Update destination register for CSR reads */
+ insn = vcpu->arch.csr_decode.insn;
+ if ((insn >> SH_RD) & MASK_RX)
+ SET_RD(insn, &vcpu->arch.guest_context,
+ run->riscv_csr.ret_value);
+
+ /* Move to next instruction */
+ vcpu->arch.guest_context.sepc += INSN_LEN(insn);
+
+ return 0;
+}
+
+static int csr_insn(struct kvm_vcpu *vcpu, struct kvm_run *run, ulong insn)
+{
+ int i, rc = KVM_INSN_ILLEGAL_TRAP;
+ unsigned int csr_num = insn >> SH_RS2;
+ unsigned int rs1_num = (insn >> SH_RS1) & MASK_RX;
+ ulong rs1_val = GET_RS1(insn, &vcpu->arch.guest_context);
+ const struct csr_func *tcfn, *cfn = NULL;
+ ulong val = 0, wr_mask = 0, new_val = 0;
+
+ /* Decode the CSR instruction */
+ switch (GET_RM(insn)) {
+ case 1:
+ wr_mask = -1UL;
+ new_val = rs1_val;
+ break;
+ case 2:
+ wr_mask = rs1_val;
+ new_val = -1UL;
+ break;
+ case 3:
+ wr_mask = rs1_val;
+ new_val = 0;
+ break;
+ case 5:
+ wr_mask = -1UL;
+ new_val = rs1_num;
+ break;
+ case 6:
+ wr_mask = rs1_num;
+ new_val = -1UL;
+ break;
+ case 7:
+ wr_mask = rs1_num;
+ new_val = 0;
+ break;
+ default:
+ return rc;
+ };
+
+ /* Save instruction decode info */
+ vcpu->arch.csr_decode.insn = insn;
+ vcpu->arch.csr_decode.return_handled = 0;
+
+ /* Update CSR details in kvm_run struct */
+ run->riscv_csr.csr_num = csr_num;
+ run->riscv_csr.new_value = new_val;
+ run->riscv_csr.write_mask = wr_mask;
+ run->riscv_csr.ret_value = 0;
+
+ /* Find in-kernel CSR function */
+ for (i = 0; i < ARRAY_SIZE(csr_funcs); i++) {
+ tcfn = &csr_funcs[i];
+ if ((tcfn->base <= csr_num) &&
+ (csr_num < (tcfn->base + tcfn->count))) {
+ cfn = tcfn;
+ break;
+ }
+ }
+
+ /* First try in-kernel CSR emulation */
+ if (cfn && cfn->func) {
+ rc = cfn->func(vcpu, csr_num, &val, new_val, wr_mask);
+ if (rc > KVM_INSN_EXIT_TO_USER_SPACE) {
+ if (rc == KVM_INSN_CONTINUE_NEXT_SEPC) {
+ run->riscv_csr.ret_value = val;
+ vcpu->stat.csr_exit_kernel++;
+ kvm_riscv_vcpu_csr_return(vcpu, run);
+ rc = KVM_INSN_CONTINUE_SAME_SEPC;
+ }
+ return rc;
+ }
+ }
+
+ /* Exit to user-space for CSR emulation */
+ if (rc <= KVM_INSN_EXIT_TO_USER_SPACE) {
+ vcpu->stat.csr_exit_user++;
+ run->exit_reason = KVM_EXIT_RISCV_CSR;
+ }
+
+ return rc;
+}
+
static const struct insn_func system_opcode_funcs[] = {
+ {
+ .mask = INSN_MASK_CSRRW,
+ .match = INSN_MATCH_CSRRW,
+ .func = csr_insn,
+ },
+ {
+ .mask = INSN_MASK_CSRRS,
+ .match = INSN_MATCH_CSRRS,
+ .func = csr_insn,
+ },
+ {
+ .mask = INSN_MASK_CSRRC,
+ .match = INSN_MATCH_CSRRC,
+ .func = csr_insn,
+ },
+ {
+ .mask = INSN_MASK_CSRRWI,
+ .match = INSN_MATCH_CSRRWI,
+ .func = csr_insn,
+ },
+ {
+ .mask = INSN_MASK_CSRRSI,
+ .match = INSN_MATCH_CSRRSI,
+ .func = csr_insn,
+ },
+ {
+ .mask = INSN_MASK_CSRRCI,
+ .match = INSN_MATCH_CSRRCI,
+ .func = csr_insn,
+ },
{
.mask = INSN_MASK_WFI,
.match = INSN_MATCH_WFI,
@@ -270,6 +270,7 @@ struct kvm_xen_exit {
#define KVM_EXIT_X86_BUS_LOCK 33
#define KVM_EXIT_XEN 34
#define KVM_EXIT_RISCV_SBI 35
+#define KVM_EXIT_RISCV_CSR 36
/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@@ -496,6 +497,13 @@ struct kvm_run {
unsigned long args[6];
unsigned long ret[2];
} riscv_sbi;
+ /* KVM_EXIT_RISCV_CSR */
+ struct {
+ unsigned long csr_num;
+ unsigned long new_value;
+ unsigned long write_mask;
+ unsigned long ret_value;
+ } riscv_csr;
/* Fix the size of the union. */
char padding[256];
};
We add an extensible CSR emulation framework which is based upon the existing system instruction emulation. This will be useful to upcoming AIA, PMU, Nested and other virtualization features. The CSR emulation framework also has provision to emulate CSR in user space but this will be used only in very specific cases such as AIA IMSIC CSR emulation in user space or vendor specific CSR emulation in user space. By default, all CSRs not handled by KVM RISC-V will be redirected back to Guest VCPU as illegal instruction trap. Signed-off-by: Anup Patel <apatel@ventanamicro.com> --- arch/riscv/include/asm/kvm_host.h | 5 + arch/riscv/include/asm/kvm_vcpu_insn.h | 6 + arch/riscv/kvm/vcpu.c | 11 ++ arch/riscv/kvm/vcpu_insn.c | 169 +++++++++++++++++++++++++ include/uapi/linux/kvm.h | 8 ++ 5 files changed, 199 insertions(+)