LoongArch: KVM: Implement handle csr exception

Implement kvm handle LoongArch vcpu exit caused by reading, writing and
exchanging csr. Use kvm_vcpu_arch::csr structure to emulate the software
registers.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Tested-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
new file mode 100644 (file)
index 0000000..37bc8a4
--- /dev/null
+++ b/arch/loongarch/kvm/exit.c
@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2023 Loongson Technology Corporation Limited
+ */
+
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/kvm_host.h>
+#include <linux/module.h>
+#include <linux/preempt.h>
+#include <linux/vmalloc.h>
+#include <asm/fpu.h>
+#include <asm/inst.h>
+#include <asm/loongarch.h>
+#include <asm/mmzone.h>
+#include <asm/numa.h>
+#include <asm/time.h>
+#include <asm/tlb.h>
+#include <asm/kvm_csr.h>
+#include <asm/kvm_vcpu.h>
+#include "trace.h"
+
+static unsigned long kvm_emu_read_csr(struct kvm_vcpu *vcpu, int csrid)
+{
+       unsigned long val = 0;
+       struct loongarch_csrs *csr = vcpu->arch.csr;
+
+       /*
+        * From LoongArch Reference Manual Volume 1 Chapter 4.2.1
+        * For undefined CSR id, return value is 0
+        */
+       if (get_gcsr_flag(csrid) & SW_GCSR)
+               val = kvm_read_sw_gcsr(csr, csrid);
+       else
+               pr_warn_once("Unsupported csrrd 0x%x with pc %lx\n", csrid, vcpu->arch.pc);
+
+       return val;
+}
+
+static unsigned long kvm_emu_write_csr(struct kvm_vcpu *vcpu, int csrid, unsigned long val)
+{
+       unsigned long old = 0;
+       struct loongarch_csrs *csr = vcpu->arch.csr;
+
+       if (get_gcsr_flag(csrid) & SW_GCSR) {
+               old = kvm_read_sw_gcsr(csr, csrid);
+               kvm_write_sw_gcsr(csr, csrid, val);
+       } else
+               pr_warn_once("Unsupported csrwr 0x%x with pc %lx\n", csrid, vcpu->arch.pc);
+
+       return old;
+}
+
+static unsigned long kvm_emu_xchg_csr(struct kvm_vcpu *vcpu, int csrid,
+                               unsigned long csr_mask, unsigned long val)
+{
+       unsigned long old = 0;
+       struct loongarch_csrs *csr = vcpu->arch.csr;
+
+       if (get_gcsr_flag(csrid) & SW_GCSR) {
+               old = kvm_read_sw_gcsr(csr, csrid);
+               val = (old & ~csr_mask) | (val & csr_mask);
+               kvm_write_sw_gcsr(csr, csrid, val);
+               old = old & csr_mask;
+       } else
+               pr_warn_once("Unsupported csrxchg 0x%x with pc %lx\n", csrid, vcpu->arch.pc);
+
+       return old;
+}
+
+static int kvm_handle_csr(struct kvm_vcpu *vcpu, larch_inst inst)
+{
+       unsigned int rd, rj, csrid;
+       unsigned long csr_mask, val = 0;
+
+       /*
+        * CSR value mask imm
+        * rj = 0 means csrrd
+        * rj = 1 means csrwr
+        * rj != 0,1 means csrxchg
+        */
+       rd = inst.reg2csr_format.rd;
+       rj = inst.reg2csr_format.rj;
+       csrid = inst.reg2csr_format.csr;
+
+       /* Process CSR ops */
+       switch (rj) {
+       case 0: /* process csrrd */
+               val = kvm_emu_read_csr(vcpu, csrid);
+               vcpu->arch.gprs[rd] = val;
+               break;
+       case 1: /* process csrwr */
+               val = vcpu->arch.gprs[rd];
+               val = kvm_emu_write_csr(vcpu, csrid, val);
+               vcpu->arch.gprs[rd] = val;
+               break;
+       default: /* process csrxchg */
+               val = vcpu->arch.gprs[rd];
+               csr_mask = vcpu->arch.gprs[rj];
+               val = kvm_emu_xchg_csr(vcpu, csrid, csr_mask, val);
+               vcpu->arch.gprs[rd] = val;
+       }
+
+       return EMULATE_DONE;
+}