Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-04 Thread Andy Lutomirski
On Sun, Apr 3, 2016 at 7:10 AM, Borislav Petkov wrote: > On Sun, Apr 03, 2016 at 06:55:00AM -0700, Andy Lutomirski wrote: >> > No, please don't fail at early boot. >> > >> > Early boot is just about the *worst* situation to try to debug odd >> > failures, exactly since things like

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-03 Thread Borislav Petkov
On Sun, Apr 03, 2016 at 06:55:00AM -0700, Andy Lutomirski wrote: > > No, please don't fail at early boot. > > > > Early boot is just about the *worst* situation to try to debug odd > > failures, exactly since things like printk may not be reliable, and > > things won't get logged etc. > > > > So

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-03 Thread Andy Lutomirski
On Sun, Apr 3, 2016 at 6:51 AM, Linus Torvalds wrote: > On Sun, Apr 3, 2016 at 3:07 AM, Borislav Petkov wrote: >> >> I'm wondering whether making it try to EFAULT correctly is the right >> thing to do... We're certainly more conservative if we panic

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-03 Thread Linus Torvalds
On Sun, Apr 3, 2016 at 3:07 AM, Borislav Petkov wrote: > > I'm wondering whether making it try to EFAULT correctly is the right > thing to do... We're certainly more conservative if we panic and not > allow some silently failed attempt at recovery which looks successful, > to

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-03 Thread Andy Lutomirski
On Sun, Apr 3, 2016 at 1:07 AM, Borislav Petkov wrote: > On Sat, Apr 02, 2016 at 10:52:48PM +0200, Borislav Petkov wrote: >> On Sat, Apr 02, 2016 at 01:16:07PM -0700, Andy Lutomirski wrote: >> > I have no idea why it was explicitly unsupported, but I'm guessing it >> > was just to

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-03 Thread Borislav Petkov
On Sat, Apr 02, 2016 at 10:52:48PM +0200, Borislav Petkov wrote: > On Sat, Apr 02, 2016 at 01:16:07PM -0700, Andy Lutomirski wrote: > > I have no idea why it was explicitly unsupported, but I'm guessing it > > was just to avoid duplicating the code. Early "ext" uaccess failures > > are certainly

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-02 Thread Borislav Petkov
On Sat, Apr 02, 2016 at 01:16:07PM -0700, Andy Lutomirski wrote: > I have no idea why it was explicitly unsupported, but I'm guessing it > was just to avoid duplicating the code. Early "ext" uaccess failures > are certainly not going to work, but I don't think this is a problem > -- there's no

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-02 Thread Andy Lutomirski
On Sat, Apr 2, 2016 at 11:52 AM, Borislav Petkov wrote: > On Sat, Apr 02, 2016 at 07:01:35AM -0700, Andy Lutomirski wrote: >> Now that early_fixup_exception has pt_regs, we can just call >> fixup_exception from it. This will make fancy exception handlers >> work early. >> >>

Re: [Xen-devel] [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

2016-04-02 Thread Borislav Petkov
On Sat, Apr 02, 2016 at 07:01:35AM -0700, Andy Lutomirski wrote: > Now that early_fixup_exception has pt_regs, we can just call > fixup_exception from it. This will make fancy exception handlers > work early. > > Signed-off-by: Andy Lutomirski > --- > arch/x86/mm/extable.c |