Re: my simh-vax crashed: panic: pmap_enter on PG_SREF page

[Jason Thorpe <thorpej%me.com@localhost>]

> On Dec 20, 2023, at 6:59 PM, Jason Thorpe <thorpej%me.com@localhost> wrote:
> 
>> On Dec 20, 2023, at 6:50 PM, Kalvis Duckmanton <kalvisd%gmail.com@localhost> wrote:
>> 
>> On 21/12/23 13:05, Greg Oster wrote:
>>> On 2023-12-20 19.42, Johnny Billquist wrote:
>>>> Nothing concrete, except that that amount of memory did have issues in the past. We hope it had been fixed, but maybe there is some kind of issue with that much memory still? Could you try with less physical memory? Like 128M?
>>> 
>>> I've seen this error at least 3 times now too.... this last time was with 256MB, but I'm pretty sure the first two were with just 64MB RAM.
>> 
>> I've seen this also - from my notes it appeared to be due to stale entries in the translation buffer for the pages in system space holding the page table entries for P0 or P1 space.  Flushing the translation buffer when extending P0 or P1 space seems to have fixed it.  I'm attaching a patch for consideration.
> 
> That patch looks pretty reasonable, but wouldn’t it be better to invalidate the outgoing range?  Generally, best practice is to invalidate a TLB thing when it becomes invalid, rather than when it get a new value.

Maybe something like this?

	https://www.netbsd.org/~thorpej/vax-pmap-tbi-ptps-patch.txt

i.e. when the PTE in Sysmap that maps the PTP is invalidated.

-- thorpej