Commit dd856efa authored by Avi Kivity's avatar Avi Kivity Committed by Marcelo Tosatti
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KVM: x86 emulator: access GPRs on demand



Instead of populating the entire register file, read in registers
as they are accessed, and write back only the modified ones.  This
saves a VMREAD and VMWRITE on Intel (for rsp, since it is not usually
used during emulation), and a two 128-byte copies for the registers.
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent 66a03505
......@@ -85,6 +85,19 @@ struct x86_instruction_info {
#define X86EMUL_INTERCEPTED 6 /* Intercepted by nested VMCB/VMCS */
struct x86_emulate_ops {
/*
* read_gpr: read a general purpose register (rax - r15)
*
* @reg: gpr number.
*/
ulong (*read_gpr)(struct x86_emulate_ctxt *ctxt, unsigned reg);
/*
* write_gpr: write a general purpose register (rax - r15)
*
* @reg: gpr number.
* @val: value to write.
*/
void (*write_gpr)(struct x86_emulate_ctxt *ctxt, unsigned reg, ulong val);
/*
* read_std: Read bytes of standard (non-emulated/special) memory.
* Used for descriptor reading.
......@@ -281,8 +294,10 @@ struct x86_emulate_ctxt {
bool rip_relative;
unsigned long _eip;
struct operand memop;
u32 regs_valid; /* bitmaps of registers in _regs[] that can be read */
u32 regs_dirty; /* bitmaps of registers in _regs[] that have been written */
/* Fields above regs are cleared together. */
unsigned long regs[NR_VCPU_REGS];
unsigned long _regs[NR_VCPU_REGS];
struct operand *memopp;
struct fetch_cache fetch;
struct read_cache io_read;
......@@ -394,4 +409,7 @@ int emulator_task_switch(struct x86_emulate_ctxt *ctxt,
u16 tss_selector, int idt_index, int reason,
bool has_error_code, u32 error_code);
int emulate_int_real(struct x86_emulate_ctxt *ctxt, int irq);
void emulator_invalidate_register_cache(struct x86_emulate_ctxt *ctxt);
void emulator_writeback_register_cache(struct x86_emulate_ctxt *ctxt);
#endif /* _ASM_X86_KVM_X86_EMULATE_H */
This diff is collapsed.
......@@ -4313,7 +4313,19 @@ static void emulator_get_cpuid(struct x86_emulate_ctxt *ctxt,
kvm_cpuid(emul_to_vcpu(ctxt), eax, ebx, ecx, edx);
}
static ulong emulator_read_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg)
{
return kvm_register_read(emul_to_vcpu(ctxt), reg);
}
static void emulator_write_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg, ulong val)
{
kvm_register_write(emul_to_vcpu(ctxt), reg, val);
}
static struct x86_emulate_ops emulate_ops = {
.read_gpr = emulator_read_gpr,
.write_gpr = emulator_write_gpr,
.read_std = kvm_read_guest_virt_system,
.write_std = kvm_write_guest_virt_system,
.fetch = kvm_fetch_guest_virt,
......@@ -4348,14 +4360,6 @@ static struct x86_emulate_ops emulate_ops = {
.get_cpuid = emulator_get_cpuid,
};
static void cache_all_regs(struct kvm_vcpu *vcpu)
{
kvm_register_read(vcpu, VCPU_REGS_RAX);
kvm_register_read(vcpu, VCPU_REGS_RSP);
kvm_register_read(vcpu, VCPU_REGS_RIP);
vcpu->arch.regs_dirty = ~0;
}
static void toggle_interruptibility(struct kvm_vcpu *vcpu, u32 mask)
{
u32 int_shadow = kvm_x86_ops->get_interrupt_shadow(vcpu, mask);
......@@ -4382,12 +4386,10 @@ static void inject_emulated_exception(struct kvm_vcpu *vcpu)
kvm_queue_exception(vcpu, ctxt->exception.vector);
}
static void init_decode_cache(struct x86_emulate_ctxt *ctxt,
const unsigned long *regs)
static void init_decode_cache(struct x86_emulate_ctxt *ctxt)
{
memset(&ctxt->twobyte, 0,
(void *)&ctxt->regs - (void *)&ctxt->twobyte);
memcpy(ctxt->regs, regs, sizeof(ctxt->regs));
(void *)&ctxt->_regs - (void *)&ctxt->twobyte);
ctxt->fetch.start = 0;
ctxt->fetch.end = 0;
......@@ -4402,14 +4404,6 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
int cs_db, cs_l;
/*
* TODO: fix emulate.c to use guest_read/write_register
* instead of direct ->regs accesses, can save hundred cycles
* on Intel for instructions that don't read/change RSP, for
* for example.
*/
cache_all_regs(vcpu);
kvm_x86_ops->get_cs_db_l_bits(vcpu, &cs_db, &cs_l);
ctxt->eflags = kvm_get_rflags(vcpu);
......@@ -4421,7 +4415,7 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
X86EMUL_MODE_PROT16;
ctxt->guest_mode = is_guest_mode(vcpu);
init_decode_cache(ctxt, vcpu->arch.regs);
init_decode_cache(ctxt);
vcpu->arch.emulate_regs_need_sync_from_vcpu = false;
}
......@@ -4441,7 +4435,6 @@ int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq, int inc_eip)
return EMULATE_FAIL;
ctxt->eip = ctxt->_eip;
memcpy(vcpu->arch.regs, ctxt->regs, sizeof ctxt->regs);
kvm_rip_write(vcpu, ctxt->eip);
kvm_set_rflags(vcpu, ctxt->eflags);
......@@ -4599,7 +4592,7 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
changes registers values during IO operation */
if (vcpu->arch.emulate_regs_need_sync_from_vcpu) {
vcpu->arch.emulate_regs_need_sync_from_vcpu = false;
memcpy(ctxt->regs, vcpu->arch.regs, sizeof ctxt->regs);
emulator_invalidate_register_cache(ctxt);
}
restart:
......@@ -4637,7 +4630,6 @@ restart:
toggle_interruptibility(vcpu, ctxt->interruptibility);
kvm_set_rflags(vcpu, ctxt->eflags);
kvm_make_request(KVM_REQ_EVENT, vcpu);
memcpy(vcpu->arch.regs, ctxt->regs, sizeof ctxt->regs);
vcpu->arch.emulate_regs_need_sync_to_vcpu = false;
kvm_rip_write(vcpu, ctxt->eip);
} else
......@@ -5591,8 +5583,7 @@ int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
* that usually, but some bad designed PV devices (vmware
* backdoor interface) need this to work
*/
struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
memcpy(vcpu->arch.regs, ctxt->regs, sizeof ctxt->regs);
emulator_writeback_register_cache(&vcpu->arch.emulate_ctxt);
vcpu->arch.emulate_regs_need_sync_to_vcpu = false;
}
regs->rax = kvm_register_read(vcpu, VCPU_REGS_RAX);
......@@ -5723,6 +5714,7 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
{
struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
int ret;
unsigned reg;
init_emulate_ctxt(vcpu);
......@@ -5732,7 +5724,6 @@ int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
if (ret)
return EMULATE_FAIL;
memcpy(vcpu->arch.regs, ctxt->regs, sizeof ctxt->regs);
kvm_rip_write(vcpu, ctxt->eip);
kvm_set_rflags(vcpu, ctxt->eflags);
kvm_make_request(KVM_REQ_EVENT, vcpu);
......
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