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From: Lennert Buytenhek <buytenh@wantstofly.org>
To: "Suthikulpanit, Suravee" <suravee.suthikulpanit@amd.com>
Cc: iommu@lists.linux-foundation.org
Subject: Re: [PATCH] iommu/amd: Fix I/O page fault logging ratelimit test
Date: Wed, 21 Jul 2021 16:46:52 +0300	[thread overview]
Message-ID: <YPglTERWMajeo6Sj@wantstofly.org> (raw)
In-Reply-To: <79c1cd8b-c680-b3fb-08f0-47c42290d1a4@amd.com>

On Tue, Jul 20, 2021 at 07:05:50PM -0500, Suthikulpanit, Suravee wrote:

> Hi Lennert,

Hi Suravee,


> > On an AMD system, I/O page faults are usually logged like this:
> > ....
> > diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> > index 811a49a95d04..7ae426b092f2 100644
> > --- a/drivers/iommu/amd/iommu.c
> > +++ b/drivers/iommu/amd/iommu.c
> > @@ -483,7 +483,7 @@ static void amd_iommu_report_page_fault(u16 devid, u16 domain_id,
> >   	if (dev_data && __ratelimit(&dev_data->rs)) {
> >   		pci_err(pdev, "Event logged [IO_PAGE_FAULT domain=0x%04x address=0x%llx flags=0x%04x]\n",
> >   			domain_id, address, flags);
> > -	} else if (printk_ratelimit()) {
> > +	} else if (!dev_data && printk_ratelimit()) {
> 
> This seems a bit confusing. Also, according to the following comment in include/linux/printk.h:
> 
> /*
>  * Please don't use printk_ratelimit(), because it shares ratelimiting state
>  * with all other unrelated printk_ratelimit() callsites.  Instead use
>  * printk_ratelimited() or plain old __ratelimit().
>  */
> 
> We probably should move away from using printk_ratelimit() here.
> What about the following change instead?
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 811a49a95d04..8eb5d3519743 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -480,11 +480,12 @@ static void amd_iommu_report_page_fault(u16 devid, u16 domain_id,
>         if (pdev)
>                 dev_data = dev_iommu_priv_get(&pdev->dev);
> 
> -       if (dev_data && __ratelimit(&dev_data->rs)) {
> -               pci_err(pdev, "Event logged [IO_PAGE_FAULT domain=0x%04x address=0x%llx flags=0x%04x]\n",
> -                       domain_id, address, flags);
> -       } else if (printk_ratelimit()) {
> -               pr_err("Event logged [IO_PAGE_FAULT device=%02x:%02x.%x domain=0x%04x address=0x%llx flags=0x%04x]\n",
> +       if (dev_data) {
> +               if (__ratelimit(&dev_data->rs))
> +                       pci_err(pdev, "Event logged [IO_PAGE_FAULT domain=0x%04x address=0x%llx flags=0x%04x]\n",
> +                               domain_id, address, flags);
> +       } else {
> +               pr_err_ratelimited("Event logged [IO_PAGE_FAULT device=%02x:%02x.%x domain=0x%04x address=0x%llx flags=0x%04x]\n",
>                         PCI_BUS_NUM(devid), PCI_SLOT(devid), PCI_FUNC(devid),
>                         domain_id, address, flags);
>         }

Looks good!


> Note also that there might be other places in this file that would need
> similar modification as well.

Indeed, there are two more sites like these.

I've sent a new patch that incorporates your feedback.  Thank you!


Cheers,
Lennert
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      reply	other threads:[~2021-07-21 13:46 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19  0:47 [PATCH] iommu/amd: Fix I/O page fault logging ratelimit test Lennert Buytenhek
2021-07-21  0:05 ` Suthikulpanit, Suravee via iommu
2021-07-21 13:46   ` Lennert Buytenhek [this message]

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