Re: [Qemu-devel] [PATCH v5 15/17] ppc/pnv: Add cut down PSI bridge model and hookup external interrupt

[Cédric Le Goater]

On 10/25/2016 07:30 AM, David Gibson wrote:
> On Sat, Oct 22, 2016 at 11:46:48AM +0200, Cédric Le Goater wrote:
>> From: Benjamin Herrenschmidt <address@hidden>
>>
>> The PSI (Processor Service Interface) is one of the engines of the
>> "Bridge" unit which connects the different interfaces to the Power
>> Processor.
>>
>> This adds just enough of the PSI bridge to handle various on-chip and
>> the one external interrupt. The rest of PSI has to do with the link to
>> the IBM FSP service processor which we don't plan to emulate (not used
>> on OpenPower machines).
>>
>> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
>> [clg: - updated for qemu-2.7
>>       - changed the XSCOM interface to fit new model
>>       - QOMified the model
>>       - reworked set_xive ]
>> Signed-off-by: Cédric Le Goater <address@hidden>
>> ---
>>
>>  When skiboot initializes PSIHB, it fills the xives with server=0,
>>  prio=0xff, which is fine, but for some reason the last two xive
>>  settings reach the qemu MMIO region with a bogus value :
>>  
>>      pnv_psi_mmio_write: MMIO write 0x30 val 0x000000ff00000000
>>      pnv_psi_mmio_write: MMIO write 0x60 val 0x000000ff20000000
>>      pnv_psi_mmio_write: MMIO write 0x68 val 0x000000ff40000000
>>      pnv_psi_mmio_write: MMIO write 0x70 val 0x000000ff60000000
>>      pnv_psi_mmio_write: MMIO write 0x78 val 0xffffffff80000000
>>      pnv_psi_mmio_write: MMIO write 0x80 val 0xffffffffa0000000
>>
>>  It looks like a badly initialized temp variable in the call
>>  stack. The memory regions look fine, maybe in stdcix ? For the
>>  moment, I have added a logging error to catch non zero values as the
>>  guest should not do that in any case.
> 
> Just to clarify, I think you're saying that you believe this to be a
> skiboot (guest side) bug rather than a qemu bug.  Is that right?

Yes. I just found why. The P8_IRQ_PSI_* values in skiboot need to
be unsigned because they are shifted left of 29 bits :

        ...
        #define P8_IRQ_PSI_LOCAL_ERR            4
        #define P8_IRQ_PSI_EXTERNAL             5       /* Used for UART */
        ...
        out_be64(psi->regs + PSIHB_XIVR_LOCAL_ERR,
                 (0xffull << 32) | (P8_IRQ_PSI_LOCAL_ERR << 29));
        out_be64(psi->regs + PSIHB_XIVR_HOST_ERR,
                 (0xffull << 32) | (P8_IRQ_PSI_EXTERNAL << 29));


I will send a skiboot patch but we need to keep the code as it is. 

Thanks

C.