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

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Message-ID: <CALCETrUNM_xsxMKbw1nrvgaF-_bRJtfFCFFrjook0zJ=6urq-Q@mail.gmail.com>
Date:   Sun, 26 Nov 2017 07:41:11 -0800
From:   Andy Lutomirski <luto@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Andy Lutomirski <luto@...nel.org>, 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

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?