[Skiboot] [PATCH-RESEND] capi: Disable CAPP virtual machines

Stewart Smith stewart at linux.vnet.ibm.com
Thu Feb 1 19:29:20 AEDT 2018

Vaibhav Jain <vaibhav at linux.vnet.ibm.com> writes:
> When exercising more than one CAPI accelerators simultaneously in
> cache coherency mode, the verification team is seeing a deadlock. To
> fix this a workaround of disabling CAPP virtual machines is
> suggested. These 'virtual machines' let PSL queue multiple CAPP
> commands for servicing by CAPP there by increasing
> throughput. Below is the error scenario described by the h/w team:
> " With virtual machines enabled we had a deadlock scenario where with 2
> or more CAPI's in a system you could get in a deadlock scenario due to
> cast-outs that are required break the deadlock (evict lines that
> another CAPI is requesting) get stuck in the virtual machine queue by
> a command ahead of it that is being retried by the same scenario in
> the other CAPI. "
> So this patch updates CAPP APC Master Powerbus control
> register during CAPP init to also set Bit(12) that disables CAPP
> virtual machines. This forces processing of CAPP commands from PSL one
> at a time and thereby preventing above mentioned deadlock scenario.
> Signed-off-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
> ---
> Change-log:
> Resend -> Updated the patch description with more info CAPP virtual
>        	  machines and the error scenario.
> ---
>  hw/phb4.c | 1 +
>  1 file changed, 1 insertion(+)

Thanks! Merged to master as of 5a959af3fb417c4269b625d9ff2cb204f20728d5
Stewart Smith
OPAL Architect, IBM.

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