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From: Logan Gunthorpe <logang@deltatee.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-doc@vger.kernel.org, "Stephen Bates" <sbates@raithlin.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Christoffer Dall" <cdall@linaro.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	"Marc Zyngier" <marc.zyngier@arm.com>,
	"Kai-Heng Feng" <kai.heng.feng@canonical.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH 2/3] PCI: Allow specifying devices using a base bus and path of devfns
Date: Wed, 30 May 2018 11:36:01 -0600	[thread overview]
Message-ID: <d3a139c0-53d4-56cf-fa7e-8db5fb527136@deltatee.com> (raw)
In-Reply-To: <20180530102329.7423dc57@w520.home>



On 30/05/18 10:23 AM, Alex Williamson wrote:
> I like the idea, but can't we improve the implementation?  It seems
> that we shouldn't need to allocate more than a working copy of the
> original path string.  We can use strrchr() to find the last path
> divider ('/'), match the slot.fn after that to the current devfn, set
> that path divider to null, step to the next upstream device and
> repeat.  

Ok, I'll give it a shot. I thought this would be a bit more tricky, but
perhaps not.

> Also, since we're working from a downstream device up, I
> suspect we don't need to get and put references at each step, the
> downstream device probably already holds a reference to the upstream
> device for each step along the way.  

That makes sense to me. I think it's something I added in similar p2pdma
code from somebody's review. But sounds like I can probably strip it out
there too and just put a comment noting this.

Thanks,

Logan

WARNING: multiple messages have this Message-ID (diff)
From: Logan Gunthorpe <logang@deltatee.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-doc@vger.kernel.org, "Stephen Bates" <sbates@raithlin.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Christoffer Dall" <cdall@linaro.org>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	"Marc Zyngier" <marc.zyngier@arm.com>,
	"Kai-Heng Feng" <kai.heng.feng@canonical.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Christian König" <christian.koenig@amd.com>
Subject: Re: [PATCH 2/3] PCI: Allow specifying devices using a base bus and path of devfns
Date: Wed, 30 May 2018 11:36:01 -0600	[thread overview]
Message-ID: <d3a139c0-53d4-56cf-fa7e-8db5fb527136@deltatee.com> (raw)
In-Reply-To: <20180530102329.7423dc57@w520.home>



On 30/05/18 10:23 AM, Alex Williamson wrote:
> I like the idea, but can't we improve the implementation?  It seems
> that we shouldn't need to allocate more than a working copy of the
> original path string.  We can use strrchr() to find the last path
> divider ('/'), match the slot.fn after that to the current devfn, set
> that path divider to null, step to the next upstream device and
> repeat.  

Ok, I'll give it a shot. I thought this would be a bit more tricky, but
perhaps not.

> Also, since we're working from a downstream device up, I
> suspect we don't need to get and put references at each step, the
> downstream device probably already holds a reference to the upstream
> device for each step along the way.  

That makes sense to me. I think it's something I added in similar p2pdma
code from somebody's review. But sounds like I can probably strip it out
there too and just put a comment noting this.

Thanks,

Logan
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  reply	other threads:[~2018-05-30 17:36 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-24 21:48 [PATCH 0/3] Add parameter for disabling ACS redirection for P2P Logan Gunthorpe
2018-05-24 21:48 ` Logan Gunthorpe
2018-05-24 21:48 ` [PATCH 1/3] PCI: Make specifying PCI devices in kernel parameters reusable Logan Gunthorpe
2018-05-24 21:48   ` Logan Gunthorpe
2018-05-24 21:48 ` [PATCH 2/3] PCI: Allow specifying devices using a base bus and path of devfns Logan Gunthorpe
2018-05-24 21:48   ` Logan Gunthorpe
2018-05-30 16:23   ` Alex Williamson
2018-05-30 16:23     ` Alex Williamson
2018-05-30 17:36     ` Logan Gunthorpe [this message]
2018-05-30 17:36       ` Logan Gunthorpe
2018-05-24 21:48 ` [PATCH 3/3] PCI: Introduce the disable_acs_redir parameter Logan Gunthorpe
2018-05-24 21:48   ` Logan Gunthorpe
2018-05-25  8:28 ` [PATCH 0/3] Add parameter for disabling ACS redirection for P2P Christian König
2018-05-25  8:28   ` Christian König

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