Re: [Qemu-devel] interrupt handling in qemu

[Peter Maydell]

On 28 December 2011 10:42, Avi Kivity <address@hidden> wrote:
> It's possible to check for an interrupt before every instruction,
> without any overhead:
>
> - when a signal arrives, check the instruction pointer. If it points
> outside tcg code, set a flag and return.
> - consult a table indexed by the instruction pointer, that gives the
> number of bytes to the next guest instruction boundary
> - if nonzero, set a breakpoint at that boundary, and resume
> - remove the breakpoint (if set)
> - adjust the TB to return on the current instruction pointer
> - return

This assumes you have hardware breakpoints on your host, so
it's not portable.

(You also need to add a check-and-handle-flag for every return
from a helper function to TCG code, and of course you need to
actually create the instruction-boundary table. These are both
overheads.)

-- PMM