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

From: Eric W. Biederman
Date: Sat Apr 03 2010 - 13:49:25 EST


Joerg Roedel <joro@xxxxxxxxxx> writes:

> 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@xxxxxxx>
>> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
>> Cc: Neil Horman <nhorman@xxxxxxxxxxxxx>
>> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
>> Signed-off-by: Chris Wright <chrisw@xxxxxxxxxxxx>
>> ---
>> 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.

Not a problem. We require a lot of things of the kdump kernel,
and it is immediately apparent in a basic sanity test.

Eric
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