linux-kernel - Re: [BUGFIX][PATCH] pci: check for 4k resource_size alignment in sriov

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Message-ID: <CAE9FiQVKLmrryoOhyjr_rGucGGZLW=PSD=s_AjW0Za6vHCvOtg@mail.gmail.com>
Date:	Fri, 27 Jan 2012 13:05:41 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	svaidy@...ux.vnet.ibm.com
Cc:	Ram Pai <linuxram@...ibm.com>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [BUGFIX][PATCH] pci: check for 4k resource_size alignment in sriov_init

On Fri, Jan 27, 2012 at 11:10 AM, Vaidyanathan Srinivasan
<svaidy@...ux.vnet.ibm.com> wrote:
> Hi Ram and Jesse,
>
> I found a trivial issue with page size alignment check on IBM POWER
> box with 64k base page size.  In sriov_init(), changing the check from
> PAGE_SIZE (arch and config dependent) to HW_PAGE_SIZE (always 4k) was
> required to use one of the sriov adapter as PF since the
> resource_size() comes up as 0x8000 and PAGE_SIZE would be 0x10000 for
> pseries boxes.
>
> I think resource_size() could be less than SystemPageSize, but I would
> like your comments/ack/nack on any consequences of checking for only
> 4k alignment here in a system with larger base page size.
>
> Thanks,
> Vaidy
>
> ---
>
>    pci: check for 4k resource_size alignment in sriov_init
>
>    pci sriov_init should check for 4k page size alignment of resource_size
>    even if base page size is larger -- like 64k in powerpc.
>
>    Signed-off-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 0321fa3..5816fa0 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -474,7 +474,7 @@ found:
>                                     pos + PCI_SRIOV_BAR + i * 4);
>                if (!res->flags)
>                        continue;
> -               if (resource_size(res) & (PAGE_SIZE - 1)) {
> +               if (resource_size(res) & (HW_PAGE_SIZE - 1)) {
>                        rc = -EIO;
>                        goto failed;
>                }
>

but HW_PAGE_SIZE is only defined for powerpc.

also there is PAGE_SHIFT around in that function.

maybe you can just define another MARCO according to IOV spec?

Thanks

Yinghai
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