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KVM: nVMX: Decoding memory operands of VMX instructions

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This patch includes a utility function for decoding pointer operands of VMX
instructions issued by L1 (a guest hypervisor)

Signed-off-by: Nadav Har'El <nyh@il.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Nadav Har'El 2011-05-25 23:04:56 +03:00 committed by Avi Kivity
parent b87a51ae28
commit 064aea7747
3 changed files with 59 additions and 1 deletions
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53
arch/x86/kvm/vmx.c
View file

@ -4342,6 +4342,59 @@ static int handle_vmoff(struct kvm_vcpu *vcpu)
return 1;
}
/*
* Decode the memory-address operand of a vmx instruction, as recorded on an
* exit caused by such an instruction (run by a guest hypervisor).
* On success, returns 0. When the operand is invalid, returns 1 and throws
* #UD or #GP.
*/
static int get_vmx_mem_address(struct kvm_vcpu *vcpu,
unsigned long exit_qualification,
u32 vmx_instruction_info, gva_t *ret)
{
/*
* According to Vol. 3B, "Information for VM Exits Due to Instruction
* Execution", on an exit, vmx_instruction_info holds most of the
* addressing components of the operand. Only the displacement part
* is put in exit_qualification (see 3B, "Basic VM-Exit Information").
* For how an actual address is calculated from all these components,
* refer to Vol. 1, "Operand Addressing".
*/
int scaling = vmx_instruction_info & 3;
int addr_size = (vmx_instruction_info >> 7) & 7;
bool is_reg = vmx_instruction_info & (1u << 10);
int seg_reg = (vmx_instruction_info >> 15) & 7;
int index_reg = (vmx_instruction_info >> 18) & 0xf;
bool index_is_valid = !(vmx_instruction_info & (1u << 22));
int base_reg = (vmx_instruction_info >> 23) & 0xf;
bool base_is_valid = !(vmx_instruction_info & (1u << 27));
if (is_reg) {
kvm_queue_exception(vcpu, UD_VECTOR);
return 1;
}
/* Addr = segment_base + offset */
/* offset = base + [index * scale] + displacement */
*ret = vmx_get_segment_base(vcpu, seg_reg);
if (base_is_valid)
*ret += kvm_register_read(vcpu, base_reg);
if (index_is_valid)
*ret += kvm_register_read(vcpu, index_reg)<<scaling;
*ret += exit_qualification; /* holds the displacement */
if (addr_size == 1) /* 32 bit */
*ret &= 0xffffffff;
/*
* TODO: throw #GP (and return 1) in various cases that the VM*
* instructions require it - e.g., offset beyond segment limit,
* unusable or unreadable/unwritable segment, non-canonical 64-bit
* address, and so on. Currently these are not checked.
*/
return 0;
}
/*
* The exit handlers return 1 if the exit was handled fully and guest execution
* may resume. Otherwise they set the kvm_run parameter to indicate what needs

3
arch/x86/kvm/x86.c
View file

@ -3848,7 +3848,7 @@ static int kvm_fetch_guest_virt(struct x86_emulate_ctxt *ctxt,
exception);
}
static int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
gva_t addr, void *val, unsigned int bytes,
struct x86_exception *exception)
{
@ -3858,6 +3858,7 @@ static int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
return kvm_read_guest_virt_helper(addr, val, bytes, vcpu, access,
exception);
}
EXPORT_SYMBOL_GPL(kvm_read_guest_virt);
static int kvm_read_guest_virt_system(struct x86_emulate_ctxt *ctxt,
gva_t addr, void *val, unsigned int bytes,

4
arch/x86/kvm/x86.h
View file

@ -81,4 +81,8 @@ int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip);
void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);
int kvm_read_guest_virt(struct x86_emulate_ctxt *ctxt,
gva_t addr, void *val, unsigned int bytes,
struct x86_exception *exception);
#endif