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KVM: Cleanup string I/O instruction emulation
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Both vmx and svm decode the I/O instructions, and both botch the job,
requiring the instruction prefixes to be fetched in order to completely
decode the instruction.

So, if we see a string I/O instruction, use the x86 emulator to decode it,
as it already has all the prefix decoding machinery.

This patch defines ins/outs opcodes in x86_emulate.c and calls
emulate_instruction() from io_interception() (svm.c) and from handle_io()
(vmx.c).  It removes all vmx/svm prefix instruction decoders
(get_addr_size(), io_get_override(), io_address(), get_io_count())

Signed-off-by: Laurent Vivier <Laurent.Vivier@bull.net>
Signed-off-by: Avi Kivity <avi@qumranet.com>
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Laurent Vivier authored and Avi Kivity committed Oct 13, 2007
1 parent 9fdaaac commit e70669a
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Showing 4 changed files with 69 additions and 208 deletions.
3 changes: 3 additions & 0 deletions drivers/kvm/kvm_main.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1221,7 +1221,10 @@ int emulate_instruction(struct kvm_vcpu *vcpu,
emulate_ctxt.fs_base = get_segment_base(vcpu, VCPU_SREG_FS);

vcpu->mmio_is_write = 0;
vcpu->pio.string = 0;
r = x86_emulate_memop(&emulate_ctxt, &emulate_ops);
if (vcpu->pio.string)
return EMULATE_DO_MMIO;

if ((r || vcpu->mmio_is_write) && run) {
run->exit_reason = KVM_EXIT_MMIO;
Expand Down
149 changes: 10 additions & 139 deletions drivers/kvm/svm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -98,20 +98,6 @@ static inline u32 svm_has(u32 feat)
return svm_features & feat;
}

static unsigned get_addr_size(struct vcpu_svm *svm)
{
struct vmcb_save_area *sa = &svm->vmcb->save;
u16 cs_attrib;

if (!(sa->cr0 & X86_CR0_PE) || (sa->rflags & X86_EFLAGS_VM))
return 2;

cs_attrib = sa->cs.attrib;

return (cs_attrib & SVM_SELECTOR_L_MASK) ? 8 :
(cs_attrib & SVM_SELECTOR_DB_MASK) ? 4 : 2;
}

static inline u8 pop_irq(struct kvm_vcpu *vcpu)
{
int word_index = __ffs(vcpu->irq_summary);
Expand Down Expand Up @@ -995,147 +981,32 @@ static int shutdown_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
return 0;
}

static int io_get_override(struct vcpu_svm *svm,
struct vmcb_seg **seg,
int *addr_override)
{
u8 inst[MAX_INST_SIZE];
unsigned ins_length;
gva_t rip;
int i;

rip = svm->vmcb->save.rip;
ins_length = svm->next_rip - rip;
rip += svm->vmcb->save.cs.base;

if (ins_length > MAX_INST_SIZE)
printk(KERN_DEBUG
"%s: inst length err, cs base 0x%llx rip 0x%llx "
"next rip 0x%llx ins_length %u\n",
__FUNCTION__,
svm->vmcb->save.cs.base,
svm->vmcb->save.rip,
svm->vmcb->control.exit_info_2,
ins_length);

if (emulator_read_std(rip, inst, ins_length, &svm->vcpu)
!= X86EMUL_CONTINUE)
/* #PF */
return 0;

*addr_override = 0;
*seg = NULL;
for (i = 0; i < ins_length; i++)
switch (inst[i]) {
case 0xf0:
case 0xf2:
case 0xf3:
case 0x66:
continue;
case 0x67:
*addr_override = 1;
continue;
case 0x2e:
*seg = &svm->vmcb->save.cs;
continue;
case 0x36:
*seg = &svm->vmcb->save.ss;
continue;
case 0x3e:
*seg = &svm->vmcb->save.ds;
continue;
case 0x26:
*seg = &svm->vmcb->save.es;
continue;
case 0x64:
*seg = &svm->vmcb->save.fs;
continue;
case 0x65:
*seg = &svm->vmcb->save.gs;
continue;
default:
return 1;
}
printk(KERN_DEBUG "%s: unexpected\n", __FUNCTION__);
return 0;
}

static unsigned long io_address(struct vcpu_svm *svm, int ins, gva_t *address)
{
unsigned long addr_mask;
unsigned long *reg;
struct vmcb_seg *seg;
int addr_override;
struct vmcb_save_area *save_area = &svm->vmcb->save;
u16 cs_attrib = save_area->cs.attrib;
unsigned addr_size = get_addr_size(svm);

if (!io_get_override(svm, &seg, &addr_override))
return 0;

if (addr_override)
addr_size = (addr_size == 2) ? 4: (addr_size >> 1);

if (ins) {
reg = &svm->vcpu.regs[VCPU_REGS_RDI];
seg = &svm->vmcb->save.es;
} else {
reg = &svm->vcpu.regs[VCPU_REGS_RSI];
seg = (seg) ? seg : &svm->vmcb->save.ds;
}

addr_mask = ~0ULL >> (64 - (addr_size * 8));

if ((cs_attrib & SVM_SELECTOR_L_MASK) &&
!(svm->vmcb->save.rflags & X86_EFLAGS_VM)) {
*address = (*reg & addr_mask);
return addr_mask;
}

if (!(seg->attrib & SVM_SELECTOR_P_SHIFT)) {
svm_inject_gp(&svm->vcpu, 0);
return 0;
}

*address = (*reg & addr_mask) + seg->base;
return addr_mask;
}

static int io_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
{
u32 io_info = svm->vmcb->control.exit_info_1; //address size bug?
int size, down, in, string, rep;
unsigned port;
unsigned long count;
gva_t address = 0;

++svm->vcpu.stat.io_exits;

svm->next_rip = svm->vmcb->control.exit_info_2;

string = (io_info & SVM_IOIO_STR_MASK) != 0;

if (string) {
if (emulate_instruction(&svm->vcpu, kvm_run, 0, 0) == EMULATE_DO_MMIO)
return 0;
return 1;
}

in = (io_info & SVM_IOIO_TYPE_MASK) != 0;
port = io_info >> 16;
size = (io_info & SVM_IOIO_SIZE_MASK) >> SVM_IOIO_SIZE_SHIFT;
string = (io_info & SVM_IOIO_STR_MASK) != 0;
rep = (io_info & SVM_IOIO_REP_MASK) != 0;
count = 1;
down = (svm->vmcb->save.rflags & X86_EFLAGS_DF) != 0;

if (string) {
unsigned addr_mask;

addr_mask = io_address(svm, in, &address);
if (!addr_mask) {
printk(KERN_DEBUG "%s: get io address failed\n",
__FUNCTION__);
return 1;
}

if (rep)
count = svm->vcpu.regs[VCPU_REGS_RCX] & addr_mask;
}
return kvm_setup_pio(&svm->vcpu, kvm_run, in, size, count, string,
down, address, rep, port);
return kvm_setup_pio(&svm->vcpu, kvm_run, in, size, 1, 0,
down, 0, rep, port);
}

static int nop_on_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)
Expand Down
76 changes: 12 additions & 64 deletions drivers/kvm/vmx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1763,82 +1763,30 @@ static int handle_triple_fault(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
return 0;
}

static int get_io_count(struct kvm_vcpu *vcpu, unsigned long *count)
{
u64 inst;
gva_t rip;
int countr_size;
int i;

if ((vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_VM)) {
countr_size = 2;
} else {
u32 cs_ar = vmcs_read32(GUEST_CS_AR_BYTES);

countr_size = (cs_ar & AR_L_MASK) ? 8:
(cs_ar & AR_DB_MASK) ? 4: 2;
}

rip = vmcs_readl(GUEST_RIP);
if (countr_size != 8)
rip += vmcs_readl(GUEST_CS_BASE);

if (emulator_read_std(rip, &inst, sizeof(inst), vcpu) !=
X86EMUL_CONTINUE)
return 0;

for (i = 0; i < sizeof(inst); i++) {
switch (((u8*)&inst)[i]) {
case 0xf0:
case 0xf2:
case 0xf3:
case 0x2e:
case 0x36:
case 0x3e:
case 0x26:
case 0x64:
case 0x65:
case 0x66:
break;
case 0x67:
countr_size = (countr_size == 2) ? 4: (countr_size >> 1);
default:
goto done;
}
}
return 0;
done:
countr_size *= 8;
*count = vcpu->regs[VCPU_REGS_RCX] & (~0ULL >> (64 - countr_size));
//printk("cx: %lx\n", vcpu->regs[VCPU_REGS_RCX]);
return 1;
}

static int handle_io(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
{
u64 exit_qualification;
int size, down, in, string, rep;
unsigned port;
unsigned long count;
gva_t address;

++vcpu->stat.io_exits;
exit_qualification = vmcs_read64(EXIT_QUALIFICATION);
in = (exit_qualification & 8) != 0;
size = (exit_qualification & 7) + 1;
string = (exit_qualification & 16) != 0;

if (string) {
if (emulate_instruction(vcpu, kvm_run, 0, 0) == EMULATE_DO_MMIO)
return 0;
return 1;
}

size = (exit_qualification & 7) + 1;
in = (exit_qualification & 8) != 0;
down = (vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_DF) != 0;
count = 1;
rep = (exit_qualification & 32) != 0;
port = exit_qualification >> 16;
address = 0;
if (string) {
if (rep && !get_io_count(vcpu, &count))
return 1;
address = vmcs_readl(GUEST_LINEAR_ADDRESS);
}
return kvm_setup_pio(vcpu, kvm_run, in, size, count, string, down,
address, rep, port);

return kvm_setup_pio(vcpu, kvm_run, in, size, 1, 0, down,
0, rep, port);
}

static void
Expand Down
49 changes: 44 additions & 5 deletions drivers/kvm/x86_emulate.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -103,9 +103,12 @@ static u8 opcode_table[256] = {
/* 0x58 - 0x5F */
ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
ImplicitOps, ImplicitOps, ImplicitOps, ImplicitOps,
/* 0x60 - 0x6F */
/* 0x60 - 0x6B */
0, 0, 0, DstReg | SrcMem32 | ModRM | Mov /* movsxd (x86/64) */ ,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
/* 0x6C - 0x6F */
SrcNone | ByteOp | ImplicitOps, SrcNone | ImplicitOps, /* insb, insw/insd */
SrcNone | ByteOp | ImplicitOps, SrcNone | ImplicitOps, /* outsb, outsw/outsd */
/* 0x70 - 0x7F */
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
/* 0x80 - 0x87 */
Expand Down Expand Up @@ -428,10 +431,11 @@ struct operand {
})

/* Access/update address held in a register, based on addressing mode. */
#define address_mask(reg) \
((ad_bytes == sizeof(unsigned long)) ? \
(reg) : ((reg) & ((1UL << (ad_bytes << 3)) - 1)))
#define register_address(base, reg) \
((base) + ((ad_bytes == sizeof(unsigned long)) ? (reg) : \
((reg) & ((1UL << (ad_bytes << 3)) - 1))))

((base) + address_mask(reg))
#define register_address_increment(reg, inc) \
do { \
/* signed type ensures sign extension to long */ \
Expand Down Expand Up @@ -1116,6 +1120,41 @@ x86_emulate_memop(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
special_insn:
if (twobyte)
goto twobyte_special_insn;
switch(b) {
case 0x6c: /* insb */
case 0x6d: /* insw/insd */
if (kvm_setup_pio(ctxt->vcpu, NULL,
1, /* in */
(d & ByteOp) ? 1 : op_bytes, /* size */
rep_prefix ?
address_mask(_regs[VCPU_REGS_RCX]) : 1, /* count */
1, /* strings */
(_eflags & EFLG_DF), /* down */
register_address(ctxt->es_base,
_regs[VCPU_REGS_RDI]), /* address */
rep_prefix,
_regs[VCPU_REGS_RDX] /* port */
) == 0)
return -1;
return 0;
case 0x6e: /* outsb */
case 0x6f: /* outsw/outsd */
if (kvm_setup_pio(ctxt->vcpu, NULL,
0, /* in */
(d & ByteOp) ? 1 : op_bytes, /* size */
rep_prefix ?
address_mask(_regs[VCPU_REGS_RCX]) : 1, /* count */
1, /* strings */
(_eflags & EFLG_DF), /* down */
register_address(override_base ?
*override_base : ctxt->ds_base,
_regs[VCPU_REGS_RSI]), /* address */
rep_prefix,
_regs[VCPU_REGS_RDX] /* port */
) == 0)
return -1;
return 0;
}
if (rep_prefix) {
if (_regs[VCPU_REGS_RCX] == 0) {
ctxt->vcpu->rip = _eip;
Expand Down

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