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Subject: Re: [PATCH v3 06/27] ocxl: Tally up the LPC memory on a link &
 allow it to be mapped
From:   "Alastair D'Silva" <alastair@au1.ibm.com>
To:     Frederic Barrat <fbarrat@linux.ibm.com>
Cc:     "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        "Oliver O'Halloran" <oohall@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Donnellan <ajd@linux.ibm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Rob Herring <robh@kernel.org>,
        Anton Blanchard <anton@ozlabs.org>,
        Krzysztof Kozlowski <krzk@kernel.org>,
        Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
        =?ISO-8859-1?Q?C=E9dric?= Le Goater <clg@kaod.org>,
        Anju T Sudhakar <anju@linux.vnet.ibm.com>,
        Hari Bathini <hbathini@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kurz <groug@kaod.org>,
        Nicholas Piggin <npiggin@gmail.com>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        Alexey Kardashevskiy <aik@ozlabs.ru>,
        linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        linux-nvdimm@lists.01.org, linux-mm@kvack.org
Date:   Wed, 26 Feb 2020 11:29:16 +1100
In-Reply-To: <4c8f704b-5607-5ca0-c00e-01e412117f6b@linux.ibm.com>
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         <20200221032720.33893-7-alastair@au1.ibm.com>
         <4c8f704b-5607-5ca0-c00e-01e412117f6b@linux.ibm.com>
Organization: IBM Australia
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On Tue, 2020-02-25 at 17:30 +0100, Frederic Barrat wrote:
> 
> Le 21/02/2020 à 04:26, Alastair D'Silva a écrit :
> > From: Alastair D'Silva <alastair@d-silva.org>
> > 
> > Tally up the LPC memory on an OpenCAPI link & allow it to be mapped
> > 
> > Signed-off-by: Alastair D'Silva <alastair@d-silva.org>
> > ---
> >   drivers/misc/ocxl/core.c          | 10 ++++++
> >   drivers/misc/ocxl/link.c          | 53
> > +++++++++++++++++++++++++++++++
> >   drivers/misc/ocxl/ocxl_internal.h | 33 +++++++++++++++++++
> >   3 files changed, 96 insertions(+)
> > 
> > diff --git a/drivers/misc/ocxl/core.c b/drivers/misc/ocxl/core.c
> > index b7a09b21ab36..2531c6cf19a0 100644
> > --- a/drivers/misc/ocxl/core.c
> > +++ b/drivers/misc/ocxl/core.c
> > @@ -230,8 +230,18 @@ static int configure_afu(struct ocxl_afu *afu,
> > u8 afu_idx, struct pci_dev *dev)
> >   	if (rc)
> >   		goto err_free_pasid;
> >   
> > +	if (afu->config.lpc_mem_size || afu-
> > >config.special_purpose_mem_size) {
> > +		rc = ocxl_link_add_lpc_mem(afu->fn->link, afu-
> > >config.lpc_mem_offset,
> > +					   afu->config.lpc_mem_size +
> > +					   afu-
> > >config.special_purpose_mem_size);
> > +		if (rc)
> > +			goto err_free_mmio;
> > +	}
> > +
> >   	return 0;
> >   
> > +err_free_mmio:
> > +	unmap_mmio_areas(afu);
> >   err_free_pasid:
> >   	reclaim_afu_pasid(afu);
> >   err_free_actag:
> > diff --git a/drivers/misc/ocxl/link.c b/drivers/misc/ocxl/link.c
> > index 58d111afd9f6..1e039cc5ebe5 100644
> > --- a/drivers/misc/ocxl/link.c
> > +++ b/drivers/misc/ocxl/link.c
> > @@ -84,6 +84,11 @@ struct ocxl_link {
> >   	int dev;
> >   	atomic_t irq_available;
> >   	struct spa *spa;
> > +	struct mutex lpc_mem_lock; /* protects lpc_mem & lpc_mem_sz */
> > +	u64 lpc_mem_sz; /* Total amount of LPC memory presented on the
> > link */
> > +	u64 lpc_mem;
> > +	int lpc_consumers;
> > +
> >   	void *platform_data;
> >   };
> >   static struct list_head links_list = LIST_HEAD_INIT(links_list);
> > @@ -396,6 +401,8 @@ static int alloc_link(struct pci_dev *dev, int
> > PE_mask, struct ocxl_link **out_l
> >   	if (rc)
> >   		goto err_spa;
> >   
> > +	mutex_init(&link->lpc_mem_lock);
> > +
> >   	/* platform specific hook */
> >   	rc = pnv_ocxl_spa_setup(dev, link->spa->spa_mem, PE_mask,
> >   				&link->platform_data);
> > @@ -711,3 +718,49 @@ void ocxl_link_free_irq(void *link_handle, int
> > hw_irq)
> >   	atomic_inc(&link->irq_available);
> >   }
> >   EXPORT_SYMBOL_GPL(ocxl_link_free_irq);
> > +
> > +int ocxl_link_add_lpc_mem(void *link_handle, u64 offset, u64 size)
> > +{
> > +	struct ocxl_link *link = (struct ocxl_link *) link_handle;
> > +
> > +	// Check for overflow
> > +	if (offset > (offset + size))
> > +		return -EINVAL;
> > +
> > +	mutex_lock(&link->lpc_mem_lock);
> > +	link->lpc_mem_sz = max(link->lpc_mem_sz, offset + size);
> > +
> > +	mutex_unlock(&link->lpc_mem_lock);
> > +
> > +	return 0;
> > +}
> > +
> > +u64 ocxl_link_lpc_map(void *link_handle, struct pci_dev *pdev)
> > +{
> > +	struct ocxl_link *link = (struct ocxl_link *) link_handle;
> > +
> > +	mutex_lock(&link->lpc_mem_lock);
> > +
> > +	if(!link->lpc_mem)
> > +		link->lpc_mem = pnv_ocxl_platform_lpc_setup(pdev, link-
> > >lpc_mem_sz);
> > +
> > +	if(link->lpc_mem)
> > +		link->lpc_consumers++;
> > +	mutex_unlock(&link->lpc_mem_lock);
> > +
> > +	return link->lpc_mem;
> > +}
> > +
> > +void ocxl_link_lpc_release(void *link_handle, struct pci_dev
> > *pdev)
> > +{
> > +	struct ocxl_link *link = (struct ocxl_link *) link_handle;
> > +
> > +	mutex_lock(&link->lpc_mem_lock);
> > +	WARN_ON(--link->lpc_consumers < 0);
> 
> Here, we always decrement the lpc_consumers count. However, it was
> only 
> incremented if the mapping was setup correctly in opal.
> 
> We could arguably claim that ocxl_link_lpc_release() should only be 
> called if ocxl_link_lpc_map() succeeded, but it would make error
> path 
> handling easier if we only decrement the lpc_consumers count if 
> link->lpc_mem is set. So that we can just call
> ocxl_link_lpc_release() 
> in error paths without having to worry about triggering the WARN_ON
> message.
> 
>    Fred
> 
> 

Ok, this makes sense.

> 
> > +	if (link->lpc_consumers == 0) {
> > +		pnv_ocxl_platform_lpc_release(pdev);
> > +		link->lpc_mem = 0;
> > +	}
> > +
> > +	mutex_unlock(&link->lpc_mem_lock);
> > +}
> > diff --git a/drivers/misc/ocxl/ocxl_internal.h
> > b/drivers/misc/ocxl/ocxl_internal.h
> > index 198e4e4bc51d..d0c8c4838f42 100644
> > --- a/drivers/misc/ocxl/ocxl_internal.h
> > +++ b/drivers/misc/ocxl/ocxl_internal.h
> > @@ -142,4 +142,37 @@ int ocxl_irq_offset_to_id(struct ocxl_context
> > *ctx, u64 offset);
> >   u64 ocxl_irq_id_to_offset(struct ocxl_context *ctx, int irq_id);
> >   void ocxl_afu_irq_free_all(struct ocxl_context *ctx);
> >   
> > +/**
> > + * ocxl_link_add_lpc_mem() - Increment the amount of memory
> > required by an OpenCAPI link
> > + *
> > + * @link_handle: The OpenCAPI link handle
> > + * @offset: The offset of the memory to add
> > + * @size: The amount of memory to increment by
> > + *
> > + * Returns 0 on success, negative on overflow
> > + */
> > +int ocxl_link_add_lpc_mem(void *link_handle, u64 offset, u64
> > size);
> > +
> > +/**
> > + * ocxl_link_lpc_map() - Map the LPC memory for an OpenCAPI device
> > + * Since LPC memory belongs to a link, the whole LPC memory
> > available
> > + * on the link must be mapped in order to make it accessible to a
> > device.
> > + * @link_handle: The OpenCAPI link handle
> > + * @pdev: A device that is on the link
> > + *
> > + * Returns the address of the mapped LPC memory, or 0 on error
> > + */
> > +u64 ocxl_link_lpc_map(void *link_handle, struct pci_dev *pdev);
> > +
> > +/**
> > + * ocxl_link_lpc_release() - Release the LPC memory device for an
> > OpenCAPI device
> > + *
> > + * Offlines LPC memory on an OpenCAPI link for a device. If this
> > is the
> > + * last device on the link to release the memory, unmap it from
> > the link.
> > + *
> > + * @link_handle: The OpenCAPI link handle
> > + * @pdev: A device that is on the link
> > + */
> > +void ocxl_link_lpc_release(void *link_handle, struct pci_dev
> > *pdev);
> > +
> >   #endif /* _OCXL_INTERNAL_H_ */
> > 
-- 
Alastair D'Silva
Open Source Developer
Linux Technology Centre, IBM Australia
mob: 0423 762 819