Re: [PATCH for-5.0 v5 01/23] ppc/xive: Record the IPB in the associated NVT

["Cédric Le Goater" <clg@kaod.org>]

On 18/11/2019 16:44, Greg Kurz wrote:
> On Fri, 15 Nov 2019 17:24:14 +0100
> Cédric Le Goater <clg@kaod.org> wrote:
> 
>> When an interrupt can not be presented to a vCPU, because it is not
>> running on any of the HW treads, the XIVE presenter updates the
>> Interrupt Pending Buffer register of the associated XIVE NVT
>> structure. This is only done if backlog is activated in the END but
>> this is generally the case.
>>
>> The current code assumes that the fields of the NVT structure is
>> architected with the same layout of the thread interrupt context
>> registers. Fix this assumption and define an offset for the IPB
>> register backup value in the NVT.
>>
> 
> Does this fix a visible bug in the powernv machine ? If so,
> maybe worth describing the symptoms.

no. this is a preliminary work for escalation suppport and to dump 
the contents of the NVT table.
 
> Anyway, this seems conforment to the XIVE spec I have, so FWIW:

FYI, the NVT structure evolves in the XIVE2 specs.

C.
 
> Reviewed-by: Greg Kurz <groug@kaod.org>
> 
>> Signed-off-by: Cédric Le Goater <clg@kaod.org>
>> ---
>>  include/hw/ppc/xive_regs.h |  1 +
>>  hw/intc/xive.c             | 11 +++++++++--
>>  2 files changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/hw/ppc/xive_regs.h b/include/hw/ppc/xive_regs.h
>> index 55307cd1533c..530f232b04f8 100644
>> --- a/include/hw/ppc/xive_regs.h
>> +++ b/include/hw/ppc/xive_regs.h
>> @@ -255,6 +255,7 @@ typedef struct XiveNVT {
>>          uint32_t        w2;
>>          uint32_t        w3;
>>          uint32_t        w4;
>> +#define NVT_W4_IPB               PPC_BITMASK32(16, 23)
>>          uint32_t        w5;
>>          uint32_t        w6;
>>          uint32_t        w7;
>> diff --git a/hw/intc/xive.c b/hw/intc/xive.c
>> index 3d472e29c858..177663d2b43e 100644
>> --- a/hw/intc/xive.c
>> +++ b/hw/intc/xive.c
>> @@ -1607,14 +1607,21 @@ static void xive_router_end_notify(XiveRouter *xrtr, uint8_t end_blk,
>>       * - logical server : forward request to IVPE (not supported)
>>       */
>>      if (xive_end_is_backlog(&end)) {
>> +        uint8_t ipb;
>> +
>>          if (format == 1) {
>>              qemu_log_mask(LOG_GUEST_ERROR,
>>                            "XIVE: END %x/%x invalid config: F1 & backlog\n",
>>                            end_blk, end_idx);
>>              return;
>>          }
>> -        /* Record the IPB in the associated NVT structure */
>> -        ipb_update((uint8_t *) &nvt.w4, priority);
>> +        /*
>> +         * Record the IPB in the associated NVT structure for later
>> +         * use. The presenter will resend the interrupt when the vCPU
>> +         * is dispatched again on a HW thread.
>> +         */
>> +        ipb = xive_get_field32(NVT_W4_IPB, nvt.w4) | priority_to_ipb(priority);
>> +        nvt.w4 = xive_set_field32(NVT_W4_IPB, nvt.w4, ipb);
>>          xive_router_write_nvt(xrtr, nvt_blk, nvt_idx, &nvt, 4);
>>  
>>          /*
>