linux-kernel - Re: [PATCH 3/4] Revert "x86: disable IOMMUs on kernel crash"

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Message-ID: <20100403174128.GQ24846@8bytes.org>
Date:	Sat, 3 Apr 2010 19:41:28 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Chris Wright <chrisw@...s-sol.org>
Cc:	Joerg Roedel <joerg.roedel@....com>, nhorman@...hat.com,
	nhorman@...driver.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org, hbabu@...ibm.com,
	iommu@...ts.linux-foundation.org, ebiederm@...ssion.com,
	vgoyal@...hat.com
Subject: Re: [PATCH 3/4] Revert "x86: disable IOMMUs on kernel crash"

On Fri, Apr 02, 2010 at 06:27:54PM -0700, Chris Wright wrote:
> This effectively reverts commit 61d047be99757fd9b0af900d7abce9a13a337488.
> 
> Disabling the IOMMU can potetially allow DMA transactions to
> complete without being translated.  Leave it enabled, and allow
> crash kernel to do the IOMMU reinitialization properly.
> 
> Cc: Joerg Roedel <joerg.roedel@....com>
> Cc: Eric Biederman <ebiederm@...ssion.com>
> Cc: Neil Horman <nhorman@...driver.com>
> Cc: Vivek Goyal <vgoyal@...hat.com>
> Signed-off-by: Chris Wright <chrisw@...s-sol.org>
> ---
>  arch/x86/kernel/crash.c |    6 ------
>  1 file changed, 6 deletions(-)
> 
> --- a/arch/x86/kernel/crash.c
> +++ b/arch/x86/kernel/crash.c
> @@ -27,7 +27,6 @@
>  #include <asm/cpu.h>
>  #include <asm/reboot.h>
>  #include <asm/virtext.h>
> -#include <asm/x86_init.h>
>  
>  #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC)
>  
> @@ -103,10 +102,5 @@ void native_machine_crash_shutdown(struc
>  #ifdef CONFIG_HPET_TIMER
>  	hpet_disable();
>  #endif
> -
> -#ifdef CONFIG_X86_64
> -	x86_platform.iommu_shutdown();
> -#endif
> -
>  	crash_save_cpu(regs, safe_smp_processor_id());

Another problem: This also breaks if the kdump kernel has no
iommu-support.

	Joerg

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