On 8/27/20 12:17 PM, Edgar E. Iglesias wrote:
> On Tue, Aug 25, 2020 at 01:59:35PM -0700, Richard Henderson wrote:
>> If the last insn on a page is imm, or a branch with delay slot,
>> then end a tb early if this has not begun the tb.  If it has
>> begun the tb, then we can allow the tb to span two pages as if
>> the imm plus its consumer, or branch plus delay, or imm plus
>> branch plus delay, are a single insn.
>>
>> If the insn in the delay slot faults, then the exception handler
>> will have reset the PC to the beginning of this sequence anyway,
>> via the stored D_FLAG and BIMM_FLAG bits.
>>
>> Disable all of this when single-stepping.
> 
> 
> Hi Richard,
> 
> We've got a Linux boot that fails after applying this patch.
> It goes from always working to only working like 1 out of 3 times.
> It fails deep in user-space so I don't have a good log for it.

Hmm.  Let's just put this off for now.  I'm not 100% happy with it anyway,
since it adjusts the data structures in weird ways.


r~

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