Re: [PATCH kernel v4 04/19] powerpc/powernv: Move npu struct from pnv_phb to pci_controller

[Alexey Kardashevskiy <aik@ozlabs.ru>]

On 06/12/2018 09:40, David Gibson wrote:
> On Wed, Dec 05, 2018 at 05:17:57PM +1100, Alexey Kardashevskiy wrote:
>>
>>
>> On 05/12/2018 16:47, Alexey Kardashevskiy wrote:
>>>
>>>
>>> On 05/12/2018 16:14, David Gibson wrote:
>>>> On Fri, Nov 23, 2018 at 04:52:49PM +1100, Alexey Kardashevskiy wrote:
>>>>> The powernv PCI code stores NPU data in the pnv_phb struct. The latter
>>>>> is referenced by pci_controller::private_data. We are going to have NPU2
>>>>> support in the pseries platform as well but it does not store any
>>>>> private_data in in the pci_controller struct; and even if it did,
>>>>> it would be a different data structure.
>>>>>
>>>>> This makes npu a pointer and stores it one level higher in
>>>>> the pci_controller struct.
>>>>>
>>>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>>>>> ---
>>>>> Changes:
>>>>> v4:
>>>>> * changed subj from "powerpc/powernv: Detach npu struct from pnv_phb"
>>>>> * got rid of global list of npus - store them now in pci_controller
>>>>> * got rid of npdev_to_npu() helper
>>>>> ---
>>>>>  arch/powerpc/include/asm/pci-bridge.h    |  1 +
>>>>>  arch/powerpc/platforms/powernv/pci.h     | 16 -----
>>>>>  arch/powerpc/platforms/powernv/npu-dma.c | 81 ++++++++++++++++++------
>>>>>  3 files changed, 64 insertions(+), 34 deletions(-)
>>>>>
>>>>> diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
>>>>> index 94d4490..aee4fcc 100644
>>>>> --- a/arch/powerpc/include/asm/pci-bridge.h
>>>>> +++ b/arch/powerpc/include/asm/pci-bridge.h
>>>>> @@ -129,6 +129,7 @@ struct pci_controller {
>>>>>  #endif	/* CONFIG_PPC64 */
>>>>>  
>>>>>  	void *private_data;
>>>>> +	struct npu *npu;
>>>>>  };
>>>>>  
>>>>>  /* These are used for config access before all the PCI probing
>>>>> diff --git a/arch/powerpc/platforms/powernv/pci.h b/arch/powerpc/platforms/powernv/pci.h
>>>>> index 2131373..f2d50974 100644
>>>>> --- a/arch/powerpc/platforms/powernv/pci.h
>>>>> +++ b/arch/powerpc/platforms/powernv/pci.h
>>>>> @@ -8,9 +8,6 @@
>>>>>  
>>>>>  struct pci_dn;
>>>>>  
>>>>> -/* Maximum possible number of ATSD MMIO registers per NPU */
>>>>> -#define NV_NMMU_ATSD_REGS 8
>>>>> -
>>>>>  enum pnv_phb_type {
>>>>>  	PNV_PHB_IODA1		= 0,
>>>>>  	PNV_PHB_IODA2		= 1,
>>>>> @@ -176,19 +173,6 @@ struct pnv_phb {
>>>>>  	unsigned int		diag_data_size;
>>>>>  	u8			*diag_data;
>>>>>  
>>>>> -	/* Nvlink2 data */
>>>>> -	struct npu {
>>>>> -		int index;
>>>>> -		__be64 *mmio_atsd_regs[NV_NMMU_ATSD_REGS];
>>>>> -		unsigned int mmio_atsd_count;
>>>>> -
>>>>> -		/* Bitmask for MMIO register usage */
>>>>> -		unsigned long mmio_atsd_usage;
>>>>> -
>>>>> -		/* Do we need to explicitly flush the nest mmu? */
>>>>> -		bool nmmu_flush;
>>>>> -	} npu;
>>>>> -
>>>>>  	int p2p_target_count;
>>>>>  };
>>>>>  
>>>>> diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
>>>>> index 91d488f..7dd5c0e5 100644
>>>>> --- a/arch/powerpc/platforms/powernv/npu-dma.c
>>>>> +++ b/arch/powerpc/platforms/powernv/npu-dma.c
>>>>> @@ -327,6 +327,25 @@ struct pnv_ioda_pe *pnv_pci_npu_setup_iommu(struct pnv_ioda_pe *npe)
>>>>>  	return gpe;
>>>>>  }
>>>>>  
>>>>> +/*
>>>>> + * NPU2 ATS
>>>>> + */
>>>>> +/* Maximum possible number of ATSD MMIO registers per NPU */
>>>>> +#define NV_NMMU_ATSD_REGS 8
>>>>> +
>>>>> +/* An NPU descriptor, valid for POWER9 only */
>>>>> +struct npu {
>>>>> +	int index;
>>>>> +	__be64 *mmio_atsd_regs[NV_NMMU_ATSD_REGS];
>>>>> +	unsigned int mmio_atsd_count;
>>>>> +
>>>>> +	/* Bitmask for MMIO register usage */
>>>>> +	unsigned long mmio_atsd_usage;
>>>>> +
>>>>> +	/* Do we need to explicitly flush the nest mmu? */
>>>>> +	bool nmmu_flush;
>>>>> +};
>>>>> +
>>>>>  /* Maximum number of nvlinks per npu */
>>>>>  #define NV_MAX_LINKS 6
>>>>>  
>>>>> @@ -478,7 +497,6 @@ static void acquire_atsd_reg(struct npu_context *npu_context,
>>>>>  	int i, j;
>>>>>  	struct npu *npu;
>>>>>  	struct pci_dev *npdev;
>>>>> -	struct pnv_phb *nphb;
>>>>>  
>>>>>  	for (i = 0; i <= max_npu2_index; i++) {
>>>>>  		mmio_atsd_reg[i].reg = -1;
>>>>> @@ -493,8 +511,10 @@ static void acquire_atsd_reg(struct npu_context *npu_context,
>>>>>  			if (!npdev)
>>>>>  				continue;
>>>>>  
>>>>> -			nphb = pci_bus_to_host(npdev->bus)->private_data;
>>>>> -			npu = &nphb->npu;
>>>>> +			npu = pci_bus_to_host(npdev->bus)->npu;
>>>>> +			if (!npu)
>>>>> +				continue;
>>>>
>>>> This patch changes a bunch of places that used to unconditionally
>>>> locate an NPU now have a failure path.
>>>>
>>>> Given that this used to always have an NPU, doesn't that mean that if
>>>> the NPU is not present something has already gone wrong, and we should
>>>> WARN_ON() or something?
>>>
>>>
>>>
>>> That means this is a leftover since I dropped that npdev_to_npu helper
>>> which could help but there was no real value in it. I'll remove the
>>> check here in the next respin.
>>
>>
>> Well, technically kmalloc() can fail in pnv_npu2_init() (but not later)
>> so can (in theory) end up with an NPU PHB and npu==NULL but it is sooo
>> unlikely...
> 
> More to the point, shouldn't you then fail immediately, rather than
> leaving the NULL floating around for later code?

Not sure I am following. pnv_npu2_init() is called at boot time so
failing-and-not-leaving-null-pointer here means panic and I definitely
do not want that. I am adding !npu checks in the next respin though,
pretty much replacing firmware_has_feature(FW_FEATURE_OPAL), do i miss
anything here?




-- 
Alexey