linux-kernel - Re: [PATCH 2/5] powerpc: Map & release OpenCAPI LPC memory

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Message-Id: <df0e5246-abd2-7bf0-be3d-ae339aac4b57@linux.ibm.com>
Date:   Thu, 19 Sep 2019 10:38:03 +0200
From:   Frederic Barrat <fbarrat@...ux.ibm.com>
To:     "Alastair D'Silva" <alastair@....ibm.com>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>,
        Allison Randal <allison@...utok.net>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Vaibhav Jain <vaibhav@...ux.ibm.com>,
        Cédric Le Goater <clg@...d.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Gibson <david@...son.dropbear.id.au>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Nicholas Piggin <npiggin@...il.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] powerpc: Map & release OpenCAPI LPC memory



Le 19/09/2019 à 02:58, Alastair D'Silva a écrit :
> On Wed, 2019-09-18 at 16:03 +0200, Frederic Barrat wrote:
>>
>> Le 17/09/2019 à 03:42, Alastair D'Silva a écrit :
>>> From: Alastair D'Silva <alastair@...ilva.org>
>>>
>>> Map & release OpenCAPI LPC memory.
>>>
>>> Signed-off-by: Alastair D'Silva <alastair@...ilva.org>
>>> ---
>>>    arch/powerpc/include/asm/pnv-ocxl.h   |  2 ++
>>>    arch/powerpc/platforms/powernv/ocxl.c | 42
>>> +++++++++++++++++++++++++++
>>>    2 files changed, 44 insertions(+)
>>>
>>> diff --git a/arch/powerpc/include/asm/pnv-ocxl.h
>>> b/arch/powerpc/include/asm/pnv-ocxl.h
>>> index 7de82647e761..f8f8ffb48aa8 100644
>>> --- a/arch/powerpc/include/asm/pnv-ocxl.h
>>> +++ b/arch/powerpc/include/asm/pnv-ocxl.h
>>> @@ -32,5 +32,7 @@ extern int pnv_ocxl_spa_remove_pe_from_cache(void
>>> *platform_data, int pe_handle)
>>>    
>>>    extern int pnv_ocxl_alloc_xive_irq(u32 *irq, u64 *trigger_addr);
>>>    extern void pnv_ocxl_free_xive_irq(u32 irq);
>>> +extern u64 pnv_ocxl_platform_lpc_setup(struct pci_dev *pdev, u64
>>> size);
>>> +extern void pnv_ocxl_platform_lpc_release(struct pci_dev *pdev);
>>>    
>>>    #endif /* _ASM_PNV_OCXL_H */
>>> diff --git a/arch/powerpc/platforms/powernv/ocxl.c
>>> b/arch/powerpc/platforms/powernv/ocxl.c
>>> index 8c65aacda9c8..81393728d6a3 100644
>>> --- a/arch/powerpc/platforms/powernv/ocxl.c
>>> +++ b/arch/powerpc/platforms/powernv/ocxl.c
>>> @@ -475,6 +475,48 @@ void pnv_ocxl_spa_release(void *platform_data)
>>>    }
>>>    EXPORT_SYMBOL_GPL(pnv_ocxl_spa_release);
>>>    
>>> +u64 pnv_ocxl_platform_lpc_setup(struct pci_dev *pdev, u64 size)
>>> +{
>>> +	struct pci_controller *hose = pci_bus_to_host(pdev->bus);
>>> +	struct pnv_phb *phb = hose->private_data;
>>> +	struct pci_dn *pdn = pci_get_pdn(pdev);
>>> +	u32 bdfn = (pdn->busno << 8) | pdn->devfn;
>>
>> We can spare a call to pci_get_pdn() with
>> bdfn = (pdev->bus->number << 8) | pdev->devfn;
>>
> 
> Ok.
> 
>>
>>> +	u64 base_addr = 0;
>>> +
>>> +	int rc = opal_npu_mem_alloc(phb->opal_id, bdfn, size,
>>> &base_addr);
>>> +
>>> +	WARN_ON(rc);
>>
>> Instead of a WARN, we should catch the error and return a null
>> address
>> to the caller.
>>
> 
> base_addr will be 0 in the error case, are you suggesting we just
> remove the WARN_ON()?


Well, we don't really have any reason to keep going if the opal call 
fails, right? And anyway, I wouldn't make any assumption on the content 
of base_addr if the call fails.
But my remark was really to avoid polluting the logs with the WARN 
output. The stack backtrace and register content is scary and is not 
going to help in that situation. A proper error message is more suitable.

   Fred



>>> +
>>> +	base_addr = be64_to_cpu(base_addr);
>>> +
>>> +	rc = check_hotplug_memory_addressable(base_addr, base_addr +
>>> size);
>>
>> That code is missing?
>>
> 
> That's added in the following patch on the mm list:
>   [PATCH v3 1/2] memory_hotplug: Add a bounds check to
> check_hotplug_memory_range()
> 
>>
>>> +	if (rc) {
>>> +		dev_warn(&pdev->dev,
>>> +			 "LPC memory range 0x%llx-0x%llx is not fully
>>> addressable",
>>> +			 base_addr, base_addr + size - 1);
>>> +		return 0;
>>> +	}
>>> +
>>> +
>>> +	return base_addr;
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_ocxl_platform_lpc_setup);
>>> +
>>> +void pnv_ocxl_platform_lpc_release(struct pci_dev *pdev)
>>> +{
>>> +	struct pci_controller *hose = pci_bus_to_host(pdev->bus);
>>> +	struct pnv_phb *phb = hose->private_data;
>>> +	struct pci_dn *pdn = pci_get_pdn(pdev);
>>> +	u32 bdfn;
>>> +	int rc;
>>> +
>>> +	bdfn = (pdn->busno << 8) | pdn->devfn;
>>> +	rc = opal_npu_mem_release(phb->opal_id, bdfn);
>>> +	WARN_ON(rc);
>>
>> Same comments as above.
>>
>>     Fred
>>
>>
>>
>>> +}
>>> +EXPORT_SYMBOL_GPL(pnv_ocxl_platform_lpc_release);
>>> +
>>> +
>>>    int pnv_ocxl_spa_remove_pe_from_cache(void *platform_data, int
>>> pe_handle)
>>>    {
>>>    	struct spa_data *data = (struct spa_data *) platform_data;
>>>