Re: [Xen-devel] [PATCH v2 01/10] AMD/IOMMU: restrict feature logging

From: "Woods, Brian" <Brian.Woods@amd.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
	"Woods, Brian" <Brian.Woods@amd.com>,
	"Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [Xen-devel] [PATCH v2 01/10] AMD/IOMMU: restrict feature logging
Date: Mon, 1 Jul 2019 15:59:28 +0000	[thread overview]
Message-ID: <20190701155925.GA26642@amd.com> (raw)
In-Reply-To: <5D14DE6A020000780023B97B@prv1-mh.provo.novell.com>

On Thu, Jun 27, 2019 at 09:19:06AM -0600, Jan Beulich wrote:
> The common case is all IOMMUs having the same features. Log them only
> for the first IOMMU, or for any that have a differing feature set.
> 
> Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>

Acked-by: Brian Woods <brian.woods@amd.com>

> ---
> v2: New.
> 
> --- a/xen/drivers/passthrough/amd/iommu_detect.c
> +++ b/xen/drivers/passthrough/amd/iommu_detect.c
> @@ -62,6 +62,7 @@ void __init get_iommu_features(struct am
>  {
>      u32 low, high;
>      int i = 0 ;
> +    const struct amd_iommu *first;
>      static const char *__initdata feature_str[] = {
>          "- Prefetch Pages Command", 
>          "- Peripheral Page Service Request", 
> @@ -89,6 +90,11 @@ void __init get_iommu_features(struct am
>  
>      iommu->features = ((u64)high << 32) | low;
>  
> +    /* Don't log the same set of features over and over. */
> +    first = list_first_entry(&amd_iommu_head, struct amd_iommu, list);
> +    if ( iommu != first && iommu->features == first->features )
> +        return;
> +
>      printk("AMD-Vi: IOMMU Extended Features:\n");
>  
>      while ( feature_str[i] )
> 
> 
> 

-- 
Brian Woods

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