linux-kernel - Re: [PATCH 1/5] x86, pti: fix boot problems from Global-bit setting

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Date:   Mon, 23 Apr 2018 13:50:50 +0300
From:   Aaro Koskinen <aaro.koskinen@...ia.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
CC:     <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        <mceier@...il.com>, <aarcange@...hat.com>, <luto@...nel.org>,
        <arjan@...ux.intel.com>, <bp@...en8.de>,
        <dan.j.williams@...el.com>, <dwmw2@...radead.org>,
        <gregkh@...uxfoundation.org>, <hughd@...gle.com>,
        <jpoimboe@...hat.com>, <jgross@...e.com>, <keescook@...gle.com>,
        <torvalds@...ux-foundation.org>, <namit@...are.com>,
        <peterz@...radead.org>, <tglx@...utronix.de>
Subject: Re: [PATCH 1/5] x86, pti: fix boot problems from Global-bit setting

Hi,

On Fri, Apr 20, 2018 at 03:20:19PM -0700, Dave Hansen wrote:
> Part of the global bit _setting_ patches also includes clearing the
> Global bit when we do not want it.  That is done with
> set_memory_nonglobal(), which uses change_page_attr_clear() in
> pageattr.c under the covers.
> 
> The TLB flushing code inside pageattr.c has has checks like
> BUG_ON(irqs_disabled()), looking for interrupt disabling that might
> cause deadlocks.  But, these also trip in early boot on certain
> preempt configurations.  Just copy the existing BUG_ON() sequence from
> cpa_flush_range() to the other two sites and check for early boot.
> 
> Signed-off-by: Dave Hansen <dave.hansen@...ux.intel.com>
> Fixes: 39114b7a7 (x86/pti: Never implicitly clear _PAGE_GLOBAL for kernel image)
> Reported-by: Mariusz Ceier <mceier@...il.com>
> Reported-by: Aaro Koskinen <aaro.koskinen@...ia.com>

Tested-by: Aaro Koskinen <aaro.koskinen@...ia.com>

A.

> Cc: Andrea Arcangeli <aarcange@...hat.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Arjan van de Ven <arjan@...ux.intel.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: David Woodhouse <dwmw2@...radead.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Hugh Dickins <hughd@...gle.com>
> Cc: Josh Poimboeuf <jpoimboe@...hat.com>
> Cc: Juergen Gross <jgross@...e.com>
> Cc: Kees Cook <keescook@...gle.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Nadav Amit <namit@...are.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: linux-mm@...ck.org
> ---
> 
>  b/arch/x86/mm/pageattr.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff -puN arch/x86/mm/pageattr.c~pti-glb-boot-problem-fix arch/x86/mm/pageattr.c
> --- a/arch/x86/mm/pageattr.c~pti-glb-boot-problem-fix	2018-04-20 14:10:01.086749169 -0700
> +++ b/arch/x86/mm/pageattr.c	2018-04-20 14:10:01.090749169 -0700
> @@ -172,7 +172,7 @@ static void __cpa_flush_all(void *arg)
>  
>  static void cpa_flush_all(unsigned long cache)
>  {
> -	BUG_ON(irqs_disabled());
> +	BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);
>  
>  	on_each_cpu(__cpa_flush_all, (void *) cache, 1);
>  }
> @@ -236,7 +236,7 @@ static void cpa_flush_array(unsigned lon
>  	unsigned long do_wbinvd = cache && numpages >= 1024; /* 4M threshold */
>  #endif
>  
> -	BUG_ON(irqs_disabled());
> +	BUG_ON(irqs_disabled() && !early_boot_irqs_disabled);
>  
>  	on_each_cpu(__cpa_flush_all, (void *) do_wbinvd, 1);
>  
> _