arch/mips/kvm/dyntrans.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * KVM/MIPS: Binary Patching for privileged instructions, reduces traps.
   7  *
   8  * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
   9  * Authors: Sanjay Lal <sanjayl@kymasys.com>
  10  */
  11
  12 #include <linux/errno.h>
  13 #include <linux/err.h>
  14 #include <linux/highmem.h>
  15 #include <linux/kvm_host.h>
  16 #include <linux/uaccess.h>
  17 #include <linux/vmalloc.h>
  18 #include <linux/fs.h>
  19 #include <linux/bootmem.h>
  20 #include <asm/cacheflush.h>
  21
  22 #include "commpage.h"
  23
  24 /**
  25  * kvm_mips_trans_replace() - Replace trapping instruction in guest memory.
  26  * @vcpu:       Virtual CPU.
  27  * @opc:        PC of instruction to replace.
  28  * @replace:    Instruction to write
  29  */
  30 static int kvm_mips_trans_replace(struct kvm_vcpu *vcpu, u32 *opc,
  31                                   union mips_instruction replace)
  32 {
  33         unsigned long vaddr = (unsigned long)opc;
  34         int err;
  35
  36 retry:
  37         /* The GVA page table is still active so use the Linux TLB handlers */
  38         kvm_trap_emul_gva_lockless_begin(vcpu);
  39         err = put_user(replace.word, opc);
  40         kvm_trap_emul_gva_lockless_end(vcpu);
  41
  42         if (unlikely(err)) {
  43                 /*
  44                  * We write protect clean pages in GVA page table so normal
  45                  * Linux TLB mod handler doesn't silently dirty the page.
  46                  * Its also possible we raced with a GVA invalidation.
  47                  * Try to force the page to become dirty.
  48                  */
  49                 err = kvm_trap_emul_gva_fault(vcpu, vaddr, true);
  50                 if (unlikely(err)) {
  51                         kvm_info("%s: Address unwriteable: %p\n",
  52                                  __func__, opc);
  53                         return -EFAULT;
  54                 }
  55
  56                 /*
  57                  * Try again. This will likely trigger a TLB refill, which will
  58                  * fetch the new dirty entry from the GVA page table, which
  59                  * should then succeed.
  60                  */
  61                 goto retry;
  62         }
  63         __local_flush_icache_user_range(vaddr, vaddr + 4);
  64
  65         return 0;
  66 }
  67
  68 int kvm_mips_trans_cache_index(union mips_instruction inst, u32 *opc,
  69                                struct kvm_vcpu *vcpu)
  70 {
  71         union mips_instruction nop_inst = { 0 };
  72
  73         /* Replace the CACHE instruction, with a NOP */
  74         return kvm_mips_trans_replace(vcpu, opc, nop_inst);
  75 }
  76
  77 /*
  78  * Address based CACHE instructions are transformed into synci(s). A little
  79  * heavy for just D-cache invalidates, but avoids an expensive trap
  80  */
  81 int kvm_mips_trans_cache_va(union mips_instruction inst, u32 *opc,
  82                             struct kvm_vcpu *vcpu)
  83 {
  84         union mips_instruction synci_inst = { 0 };
  85
  86         synci_inst.i_format.opcode = bcond_op;
  87         synci_inst.i_format.rs = inst.i_format.rs;
  88         synci_inst.i_format.rt = synci_op;
  89         if (cpu_has_mips_r6)
  90                 synci_inst.i_format.simmediate = inst.spec3_format.simmediate;
  91         else
  92                 synci_inst.i_format.simmediate = inst.i_format.simmediate;
  93
  94         return kvm_mips_trans_replace(vcpu, opc, synci_inst);
  95 }
  96
  97 int kvm_mips_trans_mfc0(union mips_instruction inst, u32 *opc,
  98                         struct kvm_vcpu *vcpu)
  99 {
 100         union mips_instruction mfc0_inst = { 0 };
 101         u32 rd, sel;
 102
 103         rd = inst.c0r_format.rd;
 104         sel = inst.c0r_format.sel;
 105
 106         if (rd == MIPS_CP0_ERRCTL && sel == 0) {
 107                 mfc0_inst.r_format.opcode = spec_op;
 108                 mfc0_inst.r_format.rd = inst.c0r_format.rt;
 109                 mfc0_inst.r_format.func = add_op;
 110         } else {
 111                 mfc0_inst.i_format.opcode = lw_op;
 112                 mfc0_inst.i_format.rt = inst.c0r_format.rt;
 113                 mfc0_inst.i_format.simmediate = KVM_GUEST_COMMPAGE_ADDR |
 114                         offsetof(struct kvm_mips_commpage, cop0.reg[rd][sel]);
 115 #ifdef CONFIG_CPU_BIG_ENDIAN
 116                 if (sizeof(vcpu->arch.cop0->reg[0][0]) == 8)
 117                         mfc0_inst.i_format.simmediate |= 4;
 118 #endif
 119         }
 120
 121         return kvm_mips_trans_replace(vcpu, opc, mfc0_inst);
 122 }
 123
 124 int kvm_mips_trans_mtc0(union mips_instruction inst, u32 *opc,
 125                         struct kvm_vcpu *vcpu)
 126 {
 127         union mips_instruction mtc0_inst = { 0 };
 128         u32 rd, sel;
 129
 130         rd = inst.c0r_format.rd;
 131         sel = inst.c0r_format.sel;
 132
 133         mtc0_inst.i_format.opcode = sw_op;
 134         mtc0_inst.i_format.rt = inst.c0r_format.rt;
 135         mtc0_inst.i_format.simmediate = KVM_GUEST_COMMPAGE_ADDR |
 136                 offsetof(struct kvm_mips_commpage, cop0.reg[rd][sel]);
 137 #ifdef CONFIG_CPU_BIG_ENDIAN
 138         if (sizeof(vcpu->arch.cop0->reg[0][0]) == 8)
 139                 mtc0_inst.i_format.simmediate |= 4;
 140 #endif
 141
 142         return kvm_mips_trans_replace(vcpu, opc, mtc0_inst);
 143 }