Re: [ARM32] panic when sshd responding

[Chuck Silvers <chuq%chuq.com@localhost>]

On Thu, Jun 19, 2008 at 10:08:25AM -0700, Matt Thomas wrote:
> On Jun 19, 2008, at 9:55 AM, Chris Gilbert wrote:
>> On Thu, June 19, 2008 10:49 am, Andy Shevchenko wrote:
>>> The last patch is wrong. There is some kind of lucky.
>>
>> Yes, it is :)  I discussed this with Matt, and we think the issue is that
>> pmap_kenter_pa is being a bit too paranoid in trying to avoid cache alias
>> issues.  And that's what the KASSERT is trying to detect.
>>
>> We think the right thing to do is assert there are no managed writeable
>> mappings (which there shouldn't be as the loan switches the pages to read
>> only, and so flushes the data & write back cache)
>
> Upon further thought, I think the socket loan code should use
> pmap_enter/pmap_remove instead pmap_kenter_pa/pmap_kremove.


I think the thinking already moved away from this idea, but just in case...

pages loaned to the kernel must be mapped with pmap_kenter_pa()
so that if the page is freed from its original object or anon,
the pmap_page_protect(VM_PROT_NONE) call that happens in that path
doesn't remove the kernel's mapping of the page.

-Chuck