Re: [Qemu-devel] in_asm substitute for accel=kvm:tcg

[Andriy Gapon]

on 19/09/2013 19:53 Paolo Bonzini said the following:
> Il 19/09/2013 16:36, Andriy Gapon ha scritto:
>> Not sure how the code ends up at 0x9315 after that.
> 
> Events are dropped, probably corresponding to more emulation.

I've got a trace without dropped events between the last "normal" instruction
and the loop (and also including a snippet where the same code is executed
without a problem):
...
qemu-system-x86-12024 [003] 278157.048876: kvm_emulate_insn:     0:9366:b1 10
(prot32)
 qemu-system-x86-12024 [003] 278157.048877: kvm_entry:            vcpu 0
 qemu-system-x86-12024 [003] 278157.048878: kvm_emulate_insn:     0:9368:8e d1
(prot32)
 qemu-system-x86-12024 [003] 278157.048880: kvm_entry:            vcpu 0
 qemu-system-x86-12024 [003] 278157.048882: kvm_exit:             reason
CR_ACCESS rip 0x9312 info 0 0
 qemu-system-x86-12024 [003] 278157.048883: kvm_cr:               cr_write 0 = 
0x10
 qemu-system-x86-12024 [003] 278157.048885: kvm_entry:            vcpu 0
 qemu-system-x86-12024 [003] 278157.048886: kvm_emulate_insn:     0:9315:ea 1a
93 00 00 (real)
 qemu-system-x86-12024 [003] 278157.048887: kvm_entry:            vcpu 0
 qemu-system-x86-12024 [003] 278157.048888: kvm_emulate_insn:     0:931a:31 c0
(real)
... ...
 qemu-system-x86-12024 [003] 278157.048990: kvm_set_irq:          gsi 4 level 0
source 0
 qemu-system-x86-12024 [003] 278157.048991: kvm_pic_set_irq:      chip 0 pin 4
(edge|masked)
 qemu-system-x86-12024 [003] 278157.048992: kvm_ioapic_set_irq:   pin 4 dst 0
vec=0 (Fixed|physical|edge|masked)
 qemu-system-x86-12024 [003] 278157.049001: kvm_entry:            vcpu 0
 qemu-system-x86-12024 [003] 278157.049002: kvm_exit:             reason
IO_INSTRUCTION rip 0x1e675 info 3fd0008 0
 qemu-system-x86-12024 [003] 278157.049005: kvm_emulate_insn:     a000:1e675:ec
(prot32)
 qemu-system-x86-12024 [003] 278157.049005: kvm_pio:              pio_read at
0x3fd size 1 count 1
 qemu-system-x86-12024 [003] 278157.049006: kvm_userspace_exit:   reason
KVM_EXIT_IO (2)
 qemu-system-x86-12024 [003] 278157.049024: kvm_entry:            vcpu 0
 qemu-system-x86-12024 [003] 278157.049027: kvm_exit:             reason
CR_ACCESS rip 0x9312 info 0 0
 qemu-system-x86-12024 [003] 278157.049028: kvm_cr:               cr_write 0 = 
0x10
 qemu-system-x86-12024 [003] 278157.049030: kvm_entry:            vcpu 0
 qemu-system-x86-12024 [003] 278157.049031: kvm_emulate_insn:     0:9315: (real)
 qemu-system-x86-12024 [003] 278157.049033: kvm_emulate_insn:     0:9315: (real)
 qemu-system-x86-12024 [003] 278157.049034: kvm_emulate_insn:     0:9315: (real)
...

It's strange that no instruction gets reported in those repeating "0:9315:
(real)" lines.  It's like kvm is somehow losing track of what should be executed
and just loops over the same ip without actually doing anything.

-- 
Andriy Gapon