Hi Julien,
On 21/02/2022 19:13, Julien Grall wrote:
On 21/02/2022 19:05, Ayan Kumar Halder wrote:
If we (ie Xen) didn't decode the instruction manually, then
check_p2m() has not been invoked yet. This is because of the
following (info.dabt.valid == True) :-
if ( !is_data || !info.dabt.valid )
{
...
if ( check_p2m(is_data, gpa) )
return;
...
}
So, in this scenario ( !info.dabt.valid), it would not be necessary
to invoke check_p2m() after try_handle_mmio().
However, if we havenot decoded the instruction manually (ie
info.dabt.valid == True), and try_handle_mmio() returns IO_UNHANDLED,
then it will be necessary to invoke "check_p2m(is_data, gpa)"
Hmmm you are right. But this doesn't seem to match the code you wrote
below. What did I miss?
My code was not correct. I have rectified it as below. Please let me
know if it looks sane.
<snip>
case FSC_FLT_TRANS:
{
info.gpa = gpa;
info.dabt = hsr.dabt;
/*
* Assumption :- Most of the times when we get a data abort and
the ISS
* is invalid or an instruction abort, the underlying cause is
that the
* page tables have not been set up correctly.
*/
if ( !is_data || !info.dabt.valid )
{
if ( check_p2m(is_data, gpa) )
return;
/*
* If the instruction abort could not be resolved by
setting the
* appropriate bits in the translation table, then Xen should
* forward the abort to the guest.
*/
if ( !is_data )
goto inject_abt;
try_decode_instruction(regs, &info);
/*
* If Xen could not decode the instruction or encountered
an error
* while decoding, then it should forward the abort to the
guest.
*/
if ( info.dabt_instr.state == INSTR_ERROR )
goto inject_abt;
}
state = try_handle_mmio(regs, &info);
switch ( state )
{
case IO_ABORT:
goto inject_abt;
case IO_HANDLED:
/*
* If the instruction was decoded and has executed
successfully
* on the MMIO region, then Xen should execute the next
part of
* the instruction. (for eg increment the rn if it is a
* post-indexing instruction.
*/
post_increment_register(&info.dabt_instr);
advance_pc(regs, hsr);
return;
case IO_RETRY:
/* finish later */
return;
case IO_UNHANDLED:
/* IO unhandled, try another way to handle it. */
break;
}
/*
* If the instruction was valid but Xen could not emulate the
instruction
* then it should configure the page tables to set the correct
page table
* entry corresponding to the faulting address. If it was
successful, it
* should return to the guest to retry the instruction (hoping
that the
* instruction will not be trapped to Xen again).
* However, if Xen was not successful in setting the page
tables, then
* it should forward the abort to the guest.
*/
if ( info.dabt.valid && check_p2m(is_data, gpa) )
return;
break;
}
default:
<snip>
- Ayan
Cheers,
