linux-kernel - Re: Is: x86: mm: Fix vmalloc_fault oops during lazy MMU updates Was: Re: [PATCH] mm/x86: Flush lazy MMU when DEBUG

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Message-ID: <20130228153846.GA9782@pd.tnic>
Date:	Thu, 28 Feb 2013 16:38:46 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>, mingo@...hat.com,
	tglx@...utronix.de, xen-devel@...ts.xen.org,
	linux-kernel@...r.kernel.org, samu.kallio@...rdeencloud.com,
	kraman@...hat.com, jwboyer@...hat.com
Subject: Re: Is: x86: mm: Fix vmalloc_fault oops during lazy MMU updates Was:
 Re: [PATCH] mm/x86: Flush lazy MMU when DEBUG_PAGEALLOC is set

On Thu, Feb 28, 2013 at 09:29:10AM -0500, Konrad Rzeszutek Wilk wrote:
> diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
> index fb674fd..4f7d793 100644
> --- a/arch/x86/mm/fault.c
> +++ b/arch/x86/mm/fault.c
> @@ -378,10 +378,12 @@ static noinline __kprobes int vmalloc_fault(unsigned long address)
>  	if (pgd_none(*pgd_ref))
>  		return -1;
>  
> -	if (pgd_none(*pgd))
> +	if (pgd_none(*pgd)) {
>  		set_pgd(pgd, *pgd_ref);
> -	else
> +		arch_flush_lazy_mmu_mode();

Do I understand it correctly that this would cost us a
"preempt_disable(); preempt_enable()" needlessly on baremetal when
running with CONFIG_PARAVIRT enabled?

Thanks.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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