KVM: emulate: put pointers in the fetch_cache

This simplifies the code a bit, especially the overflow checks.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_emulate.h b/arch/x86/include/asm/kvm_emulate.h
index fcf58cd..eb18117 100644 (file)
--- a/arch/x86/include/asm/kvm_emulate.h
+++ b/arch/x86/include/asm/kvm_emulate.h
@@ -242,8 +242,8 @@ struct operand {
 
 struct fetch_cache {
        u8 data[15];
-       unsigned long start;
-       unsigned long end;
+       u8 *ptr;
+       u8 *end;
 };
 
 struct read_cache {

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 02c668a..c163148 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -710,16 +710,15 @@ static int segmented_read_std(struct x86_emulate_ctxt *ctxt,
  */
 static int __do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt, int op_size)
 {
-       struct fetch_cache *fc = &ctxt->fetch;
        int rc;
-       int size, cur_size;
+       int size;
        unsigned long linear;
-
+       int cur_size = ctxt->fetch.end - ctxt->fetch.data;
        struct segmented_address addr = { .seg = VCPU_SREG_CS,
-                                         .ea  = fc->end };
-       cur_size = fc->end - fc->start;
-       size = min(15UL - cur_size,
-                  PAGE_SIZE - offset_in_page(fc->end));
+                                          .ea = ctxt->eip + cur_size };
+
+       size = min(15UL ^ cur_size,
+                  PAGE_SIZE - offset_in_page(addr.ea));
 
        /*
         * One instruction can only straddle two pages,
@@ -732,19 +731,18 @@ static int __do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt, int op_size)
        rc = __linearize(ctxt, addr, size, false, true, &linear);
        if (unlikely(rc != X86EMUL_CONTINUE))
                return rc;
-       rc = ctxt->ops->fetch(ctxt, linear, fc->data + cur_size,
+       rc = ctxt->ops->fetch(ctxt, linear, ctxt->fetch.end,
                              size, &ctxt->exception);
        if (unlikely(rc != X86EMUL_CONTINUE))
                return rc;
-       fc->end += size;
+       ctxt->fetch.end += size;
        return X86EMUL_CONTINUE;
 }
 
 static __always_inline int do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt,
                                               unsigned size)
 {
-       /* We have to be careful about overflow! */
-       if (unlikely(ctxt->_eip > ctxt->fetch.end - size))
+       if (unlikely(ctxt->fetch.end - ctxt->fetch.ptr < size))
                return __do_insn_fetch_bytes(ctxt, size);
        else
                return X86EMUL_CONTINUE;
@@ -753,26 +751,24 @@ static __always_inline int do_insn_fetch_bytes(struct x86_emulate_ctxt *ctxt,
 /* Fetch next part of the instruction being emulated. */
 #define insn_fetch(_type, _ctxt)                                       \
 ({     _type _x;                                                       \
-       struct fetch_cache *_fc;                                        \
                                                                        \
        rc = do_insn_fetch_bytes(_ctxt, sizeof(_type));                 \
        if (rc != X86EMUL_CONTINUE)                                     \
                goto done;                                              \
-       _fc = &ctxt->fetch;                                             \
-       _x = *(_type __aligned(1) *) &_fc->data[ctxt->_eip - _fc->start]; \
        ctxt->_eip += sizeof(_type);                                    \
+       _x = *(_type __aligned(1) *) ctxt->fetch.ptr;                   \
+       ctxt->fetch.ptr += sizeof(_type);                               \
        _x;                                                             \
 })
 
 #define insn_fetch_arr(_arr, _size, _ctxt)                             \
 ({                                                                     \
-       struct fetch_cache *_fc;                                        \
        rc = do_insn_fetch_bytes(_ctxt, _size);                         \
        if (rc != X86EMUL_CONTINUE)                                     \
                goto done;                                              \
-       _fc = &ctxt->fetch;                                             \
-       memcpy(_arr, &_fc->data[ctxt->_eip - _fc->start], _size);       \
        ctxt->_eip += (_size);                                          \
+       memcpy(_arr, ctxt->fetch.ptr, _size);                           \
+       ctxt->fetch.ptr += (_size);                                     \
 })
 
 /*
@@ -4228,8 +4224,8 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
        ctxt->memop.type = OP_NONE;
        ctxt->memopp = NULL;
        ctxt->_eip = ctxt->eip;
-       ctxt->fetch.start = ctxt->_eip;
-       ctxt->fetch.end = ctxt->fetch.start + insn_len;
+       ctxt->fetch.ptr = ctxt->fetch.data;
+       ctxt->fetch.end = ctxt->fetch.data + insn_len;
        ctxt->opcode_len = 1;
        if (insn_len > 0)
                memcpy(ctxt->fetch.data, insn, insn_len);

diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 33574c9..e850a7d 100644 (file)
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -721,10 +721,10 @@ TRACE_EVENT(kvm_emulate_insn,
                ),
 
        TP_fast_assign(
-               __entry->rip = vcpu->arch.emulate_ctxt.fetch.start;
                __entry->csbase = kvm_x86_ops->get_segment_base(vcpu, VCPU_SREG_CS);
-               __entry->len = vcpu->arch.emulate_ctxt._eip
-                              - vcpu->arch.emulate_ctxt.fetch.start;
+               __entry->len = vcpu->arch.emulate_ctxt.fetch.ptr
+                              - vcpu->arch.emulate_ctxt.fetch.data;
+               __entry->rip = vcpu->arch.emulate_ctxt._eip - __entry->len;
                memcpy(__entry->insn,
                       vcpu->arch.emulate_ctxt.fetch.data,
                       15);