Re: [patch V2 19/29] x86/exceptions: Split debug IST stack

2019-04-05 Thread Thomas Gleixner
On Fri, 5 Apr 2019, Sean Christopherson wrote: > On Fri, Apr 05, 2019 at 05:07:17PM +0200, Thomas Gleixner wrote: > > + /* > > +* Note, this covers the guard page between DB and DB1 as well to > > +* avoid two checks. But by all means @addr can never point into > > +* the guard page.

Re: [patch V2 19/29] x86/exceptions: Split debug IST stack

2019-04-05 Thread Sean Christopherson
On Fri, Apr 05, 2019 at 05:07:17PM +0200, Thomas Gleixner wrote: > The debug IST stack is actually two separate debug stacks to handle #DB > recursion. This is required because the CPU starts always at top of stack > on exception entry, which means on #DB recursion the second #DB would > overwrite

[patch V2 19/29] x86/exceptions: Split debug IST stack

2019-04-05 Thread Thomas Gleixner
The debug IST stack is actually two separate debug stacks to handle #DB recursion. This is required because the CPU starts always at top of stack on exception entry, which means on #DB recursion the second #DB would overwrite the stack of the first. The low level entry code therefore adjusts the t