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KVM: nVMX: Track vmcs12 offsets for shadowed VMCS fields

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The vmcs12 fields offsets are constant and known at compile time.  Store
the associated offset for each shadowed field to avoid the costly lookup
in vmcs_field_to_offset() when copying between vmcs12 and the shadow
VMCS.  Avoiding the costly lookup reduces the latency of copying by
~100 cycles in each direction.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson
2019-05-07 08:36:25 -07:00
committed by Paolo Bonzini
parent b643780562
commit 1c6f0b47fb
3 changed files with 108 additions and 119 deletions
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57
arch/x86/kvm/vmx/vmcs12.h
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@@ -394,69 +394,48 @@ static inline short vmcs_field_to_offset(unsigned long field)
#undef ROL16
/*
* Read a vmcs12 field. Since these can have varying lengths and we return
* one type, we chose the biggest type (u64) and zero-extend the return value
* to that size. Note that the caller, handle_vmread, might need to use only
* some of the bits we return here (e.g., on 32-bit guests, only 32 bits of
* 64-bit fields are to be returned).
*/
static inline int vmcs12_read_any(struct vmcs12 *vmcs12,
unsigned long field, u64 *ret)
static inline u64 vmcs12_read_any(struct vmcs12 *vmcs12, unsigned long field,
u16 offset)
{
short offset = vmcs_field_to_offset(field);
char *p;
if (offset < 0)
return offset;
p = (char *)vmcs12 + offset;
char *p = (char *)vmcs12 + offset;
switch (vmcs_field_width(field)) {
case VMCS_FIELD_WIDTH_NATURAL_WIDTH:
*ret = *((natural_width *)p);
return 0;
return *((natural_width *)p);
case VMCS_FIELD_WIDTH_U16:
*ret = *((u16 *)p);
return 0;
return *((u16 *)p);
case VMCS_FIELD_WIDTH_U32:
*ret = *((u32 *)p);
return 0;
return *((u32 *)p);
case VMCS_FIELD_WIDTH_U64:
*ret = *((u64 *)p);
return 0;
return *((u64 *)p);
default:
WARN_ON(1);
return -ENOENT;
WARN_ON_ONCE(1);
return -1;
}
}
static inline int vmcs12_write_any(struct vmcs12 *vmcs12,
unsigned long field, u64 field_value){
short offset = vmcs_field_to_offset(field);
static inline void vmcs12_write_any(struct vmcs12 *vmcs12, unsigned long field,
u16 offset, u64 field_value)
{
char *p = (char *)vmcs12 + offset;
if (offset < 0)
return offset;
switch (vmcs_field_width(field)) {
case VMCS_FIELD_WIDTH_U16:
*(u16 *)p = field_value;
return 0;
break;
case VMCS_FIELD_WIDTH_U32:
*(u32 *)p = field_value;
return 0;
break;
case VMCS_FIELD_WIDTH_U64:
*(u64 *)p = field_value;
return 0;
break;
case VMCS_FIELD_WIDTH_NATURAL_WIDTH:
*(natural_width *)p = field_value;
return 0;
break;
default:
WARN_ON(1);
return -ENOENT;
WARN_ON_ONCE(1);
break;
}
}
#endif /* __KVM_X86_VMX_VMCS12_H */