linux-kernel - Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

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Date:	Tue, 14 Jun 2016 10:24:16 -0700
From:	Dave Hansen <dave.hansen@...ux.intel.com>
To:	Lukasz Anaczkowski <lukasz.anaczkowski@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	tglx@...utronix.de, mingo@...hat.com, ak@...ux.intel.com,
	kirill.shutemov@...ux.intel.com, mhocko@...e.com,
	akpm@...ux-foundation.org, hpa@...or.com
Cc:	harish.srinivasappa@...el.com, lukasz.odzioba@...el.com,
	grzegorz.andrejczuk@...el.com, lukasz.daniluk@...el.com
Subject: Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

On 06/14/2016 10:01 AM, Lukasz Anaczkowski wrote:
> v2 (Lukasz Anaczkowski):
>     () fixed compilation breakage
...

By unconditionally defining the workaround code, even on kernels where
there is no chance of ever hitting this bug.  I think that's a pretty
poor way to do it.

Can we please stick this in one of the intel.c files, so it's only
present on CPU_SUP_INTEL builds?

Which reminds me...

> --- a/arch/x86/include/asm/pgtable_64.h
> +++ b/arch/x86/include/asm/pgtable_64.h
> @@ -178,6 +178,12 @@ extern void cleanup_highmap(void);
>  extern void init_extra_mapping_uc(unsigned long phys, unsigned long size);
>  extern void init_extra_mapping_wb(unsigned long phys, unsigned long size);
>  
> +#define ARCH_HAS_NEEDS_SWAP_PTL 1
> +static inline bool arch_needs_swap_ptl(void)
> +{
> +       return boot_cpu_has_bug(X86_BUG_PTE_LEAK);
> +}

Does this *REALLY* only affect 64-bit kernels?