Insta-reset-bootloop with r328166 and vm.pmap.pcid_enabled=1

[Ian FREISLICH]

Hi

I cannot for the life of me recall why I had vm.pmap.pcid_enabled=1 set
in loader.conf, but I did.  Most likely very historical reasons.

r328166 and later reset without dropping into the debugger during boot,
no panic message.

Ian

[Konstantin Belousov]

Post by Ian FREISLICH
Hi
I cannot for the life of me recall why I had vm.pmap.pcid_enabled=1 set
in loader.conf, but I did.  Most likely very historical reasons.
r328166 and later reset without dropping into the debugger during boot,
no panic message.

Yes, this is how it is currently behaves.
PCID can be used to optimize PTI, see https://reviews.freebsd.org/D13985.
It is used for very differrent algorithm when PTI=1, comparing with PTI=0.

[Ian FREISLICH]

Post by Konstantin Belousov

Post by Ian FREISLICH
Hi
I cannot for the life of me recall why I had vm.pmap.pcid_enabled=1 set
in loader.conf, but I did.  Most likely very historical reasons.
r328166 and later reset without dropping into the debugger during boot,
no panic message.

Yes, this is how it is currently behaves.
PCID can be used to optimize PTI, see https://reviews.freebsd.org/D13985.
It is used for very differrent algorithm when PTI=1, comparing with PTI=0.

Maybe there should be an "interlock" on these knobs, although judging
from the number of reports I'm the only that shot my foot.

Ian

[Ed Maste]

On 25 January 2018 at 17:21, Ian FREISLICH

Post by Ian FREISLICH

Post by Konstantin Belousov
Yes, this is how it is currently behaves.
PCID can be used to optimize PTI, see https://reviews.freebsd.org/D13985.
It is used for very differrent algorithm when PTI=1, comparing with PTI=0.

Maybe there should be an "interlock" on these knobs, although judging
from the number of reports I'm the only that shot my foot.

Sorry for the trouble.

Once D13985 is committed these knobs can both be set to 1 (and in fact
that will be the default configuration on Intel systems). I suspect
the commit will happen soon and until then it's just a temporary bump
inherent in running -current.