linux-kernel - Re: [PATCH v2] x86/entry: Fix assumptions that the HW TSS is at the beginning of cpu

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Date:   Sun, 26 Nov 2017 16:58:37 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Dave Hansen <dave.hansen@...el.com>, X86 ML <x86@...nel.org>,
        Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2] x86/entry: Fix assumptions that the HW TSS is at the
 beginning of cpu_tss


* Andy Lutomirski <luto@...nel.org> wrote:

> On Sun, Nov 26, 2017 at 5:48 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Dave Hansen <dave.hansen@...el.com> wrote:
> >
> >> On 11/10/2017 08:05 PM, Andy Lutomirski wrote:
> >> > -struct tss_struct doublefault_tss __cacheline_aligned = {
> >> > -   .x86_tss = {
> >> > -           .sp0            = STACK_START,
> >> > -           .ss0            = __KERNEL_DS,
> >> > -           .ldt            = 0,
> >> ...
> >> > +struct x86_hw_tss doublefault_tss __cacheline_aligned = {
> >> > +   .sp0            = STACK_START,
> >> > +   .ss0            = __KERNEL_DS,
> >> > +   .ldt            = 0,
> >> > +   .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
> >>
> >> FWIW, I really like the trend of renaming the hardware structures in
> >> such a way that it's clear that they *are* hardware structures.
> >>
> >> It might also be nice to reference the relevant SDM sections on the
> >> topic, or even to include a comment along the lines of how it get used.
> >> This chunk from the SDM is particularly relevant:
> >>
> >> "The TSS holds information important to 64-bit mode and that is not
> >> directly related to the task-switch mechanism."
> >
> > That makes sense - I've updated this patch with the following description added to
> > struct x86_hw_tss:
> 
> I've folded this in along with all the reviews so far, and a few misc
> fixes from Boris' review.  I was planning to resend the whole series
> today after I track down the kbuild error.  Does that sound good?

Could you please do a delta to the very latest WIP.x86/mm instead?

In the latest I have included the review tags already, and all the easy-to-do 
review feedback as well, so the delta should be rasonably small.

These entry bits are destined for x86/urgent real soon, so Thomas and me are 
trying to pin the tree down and do delta changes only.

If it's a simple full interdiff between your latest and WIP.x86/mm that's fine as 
well, can backmerge everything accordingly.

Thanks,

	Ingo