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

[Paolo Bonzini]

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.

> And here is original assembly code:
> rret_tramp:     movw $MEM_ESPR-0x08,%sp         # Reset stack pointer
>                 pushal                          # Save gp regs
>                 pushl %gs                       # Save
>                 pushl %fs                       #  seg
>                 pushl %ds                       #  regs
>                 pushl %es
>                 pushfl                          # Save %eflags
>                 cli                             # Disable interrupts
>                 std                             # String ops dec
>                 xorw %ax,%ax                    # Reset seg
>                 movw %ax,%ds                    #  regs
>                 movw %ax,%es                    #  (%ss is already 0)
>                 lidt idtdesc                    # Set IDT
>                 lgdt gdtdesc                    # Set GDT
>                 mov %cr0,%eax                   # Switch to protected
>                 inc %ax                         #  mode
>                 mov %eax,%cr0                   #
>                 ljmp $SEL_SCODE,$rret_tramp.1   # To 32-bit code
>                 .code32
> rret_tramp.1:   xorl %ecx,%ecx                  # Zero
>                 movb $SEL_SDATA,%cl             # Setup
>                 movw %cx,%ss                    #  32-bit
>                 movw %cx,%ds                    #  seg
>                 movw %cx,%es                    #  regs
>                 movl MEM_ESPR-0x04,%esp         # Switch to kernel stack
>                 leal 0x44(%esp,1),%esi          # Base of frame
>                 andb $~0x2,tss_desc+0x5         # Clear TSS busy
>                 movb $SEL_TSS,%cl               # Set task
>                 ltr %cx                         #  register
> 
> I can provide full logs, etc.
> Please let me know what else I could do.
> Thanks!
> -- 

1) Can you try loading the kvm_intel module with
emulate_invalid_guest_state=0?

2) What are the contents of fs and gs?  Why are they not zeroed?
Perhaps that is causing invalid guest state emulation to run, and then
something is triggering a bug in emulate_invalid_guest_state itself.

3) What is at 0x9315?

Paolo