Re: [Qemu-devel] [Qemu-ppc] [PATCH 3/5] target-ppc: Build error log

[Aravinda Prasad <aravinda@linux.vnet.ibm.com>]

On Wednesday 27 August 2014 03:20 PM, Alexander Graf wrote:
> 
> 
> On 25.08.14 15:45, Aravinda Prasad wrote:
>> Whenever there is a physical memory error due to bit
>> flips, which cannot be corrected by hardware, the error
>> is passed on to the kernel. If the memory address in
>> error belongs to guest address space then guest kernel
>> is responsible to take action. Hence the error is passed
>> on to guest via KVM by invoking 0x200 NMI vector.
>>
>> However, guest OS, as per PAPR, expects an error log
>> upon such error. This patch registers a new hcall
>> which is issued from 0x200 interrupt vector and builds
>> the error log, copies the error log to rtas space and
>> passes the address of the error log to guest
>>
>> Enhancement to KVM to perform above functionality is
>> already in upstream kernel.
>>
>> Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
> 
> Why do we have to maintain the error log inside the rtas blob? Can't we
> just create a fixed MMIO region that is backed by an error log device in
> QEMU?
> 
> Then this call would just always return that specific address and we'd
> also have a single file that deals with all of the error reporting.

PAPR requires error log to be inside rtas space. Hence guest OS
explicitly checks if error log is inside rtas space.

VALID_FWNMI_BUFFER does this check inside fwnmi_get_errinfo() in the kernel.

Regards,
Aravinda

> 
> 
> Alex
> 

-- 
Regards,
Aravinda