linux-kernel - Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 06 Nov 2009 10:15:02 +0900
From:	Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
To:	Bjorn Helgaas <bjorn.helgaas@...com>,
	Matthew Wilcox <matthew@....cx>
CC:	Jesse Barnes <jbarnes@...tuousgeek.org>, rdh@...t.sun.com,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci/pcie: Avoid unnecessary PCIe link retrains

Bjorn Helgaas wrote:
> On Thursday 05 November 2009 12:07:07 pm Matthew Wilcox wrote:
>> On Thu, Nov 05, 2009 at 12:59:25PM -0600, Bjorn Helgaas wrote:
>>> Here's another possibility, the idea being to collect all the PCIe
>>> stuff in one place.  This would require a lot of changes in the PCIe
>>> driver code, but most of them would be trivial.
>> I don't like the idea of kmallocing a 6- or 10-byte data structure
>> ... better to keep it in the pci_dev.  Maybe embedding a pcie_dev inside
>> the pci_dev would be a good idea, but unless there're more things to
>> move to it, this seems like a net loss to me.
> 
> That's true, it's not worth it for such a small structure.  I figured
> there would probably be more PCIe-related stuff that could go there,
> e.g., embedding the link_state directly.  But I haven't looked to
> see whether there actually is enough PCIe stuff to make it worthwhile.
> 

In my understanding, there are the following PCIe specific data in
struct pci_dev. It is not many.

	u8 pcie_cap;			*I added this time
	u8 pcie_type;
	struct pcie_link_state *link_state;
	unsigned int ari_enabled:1;
	unsigned int is_pcie:1;		*No longer needed and will be removed.
	unsigned int aer_firmware_first:1;

How about keeping cap offset in pci_dev so far and introducing the
following wrapper function?

static inline pcie_cap(struct pci_dev *pdev)
{
        return pdev->pcie_cap;
}

When we actually need a new data structure for PCIe-related stuff in the
future, all we need to do would be changing this wrapper like below.

static inline pcie_cap(struct pci_dev *pdev)
{
	struct pcie_dev *pcie = pdev->pcie;
	if (pcie)
		return pcie->cap;
	return 0;
}

Thanks,
Kenji Kaneshige

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/