Isaku Yamahata wrote: > On Fri, Dec 05, 2008 at 04:02:51PM +0900, Isaku Yamahata wrote: >> On Fri, Dec 05, 2008 at 02:36:25PM +0800, Zhang, Xiantao wrote: >>> Isaku Yamahata wrote: >>>> For those who want to test it, here is the slightly update patch. >>>> NOTE: this version doesn't solve the potential infinite loop >>>> which Alex is suspecting about. >>>> >>>> IA64: fix emulation of fp emulation >>>> >>>> This patch fixes bug reported as >>>> http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=1392 >>>> >>>> When pv domain case, FPSWA hypercall isn't implemented properly. >>>> So avoid the injecting floating point fault/trap at this moment. >>>> However this may cause infinite loop depending on dtlb cache. >>>> The right fix is to implement the hypercall properly however >>>> it wouldn't be very straight forward because the argument >>>> of fpswa is large and includes pointers. >>>> >>>> When hvm domain case, floating point trap case iip was incremented >>>> improperly. removed the increment >>>> >>>> Signed-off-by: Isaku Yamahata <[EMAIL PROTECTED]> >>>> >>>> diff --git a/xen/arch/ia64/vmx/vmx_fault.c >>>> b/xen/arch/ia64/vmx/vmx_fault.c --- a/xen/arch/ia64/vmx/vmx_fault.c >>>> +++ b/xen/arch/ia64/vmx/vmx_fault.c >>>> @@ -130,10 +130,8 @@ void vmx_reflect_interruption(u64 ifa, u >>>> status = handle_fpu_swa(0, regs, isr); >>>> if (!status) >>>> return; >>>> - else if (IA64_RETRY == status) { >>>> - vcpu_decrement_iip(vcpu); >>>> + else if (IA64_RETRY == status) >>>> return; >>>> - } >>>> break; >>>> >>>> case 29: // IA64_DEBUG_VECTOR >>> >>> Hi, Isaku >>> Why do you think the decrement is useless ? For trap case, the >>> iip should point to the next instruction instead of the one which >>> results in the trap. So once need retry, the iip should be back to >>> the privious one ? >> >> Ouch, you are correct. >> When I compared the handler with Linux one, I was confused. > > Hmm, more thoughts. > Trap means that the instruction was already executed, so backing iip > means the instruction will be executed twice. > The result would be wrong. For example, how about if the destination > register is one of the source register. > (Or is it safe to execute the instruction twice given that > FP trap was triggered? I'm not sure about such a corner case. need > to dig into the specs...)
Oh, that maybe a potential issue we didn't sense it before. > If we fail to get a bundle in a guest when FP trap, > we can't reexecute the instruction. We have to inject floating > point trap into guest. For HVM, injecting it to guest should be the right way to go. > Arrg, so FPSWA hypercall has to be implemented correctly? > What about HVM domain case? _______________________________________________ Xen-ia64-devel mailing list Xen-ia64-devel@lists.xensource.com http://lists.xensource.com/xen-ia64-devel
