On 29/03/16 19:26, Peter Maydell wrote: > On 29 March 2016 at 09:31, Sergey Fedorov <serge.f...@gmail.com> wrote: >> On 29/03/16 01:12, Richard Henderson wrote: >>> On 03/24/2016 08:11 AM, Paolo Bonzini wrote: >>>> There is also a case where a TB jumps to itself; it then appears twice >>>> in the list with different values in the low bits, such as this: >>>> >>>> tb->jmp_list_first = tb | 0; >>>> .--------------------' | >>>> | .-------' >>>> tb->jmp_list_next[0] = tb | 2; >>> Of course, it begs the question of why TB would be in its own list, >>> even if it does jump to itself. We only need the points-to list in >>> order to invalidate a TB and unlink it. But if TB is being >>> invalidated, we don't need to reset the jump within TB itself. >> If we're going to move tb_phys_invalidate() outside of tb_lock, we >> probably need to reset all jumps to the TB, even if it jumps to itself, >> so that it eventually finish its execution. > This is likely also the historical reason for the current code -- > originally we handled requesting a CPU exit by unlinking the TB, > so you needed to be able to detach jumps-to-self (these days we do > it by checking a flag at the start of each TB).
I'm not sure if CPU exit request is raised each time TB gets invalidated... Kind regards, Sergey