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From: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
To: Tom Murphy <tmurphy-nzgTgzXrdUbQT0dZR+AlfA@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	murphyt7-/Zw1syy4LHg@public.gmane.org
Subject: Re: [PATCH] iommu/amd: flush not present cache in iommu_map_page
Date: Wed, 24 Apr 2019 07:32:46 -0700	[thread overview]
Message-ID: <20190424143246.GA24079@infradead.org> (raw)
In-Reply-To: <20190424141900.8883-1-tmurphy-nzgTgzXrdUbQT0dZR+AlfA@public.gmane.org>

On Wed, Apr 24, 2019 at 03:18:59PM +0100, Tom Murphy via iommu wrote:
> check if there is a not-present cache present and flush it if there is.
> 
> Signed-off-by: Tom Murphy <tmurphy-nzgTgzXrdUbQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/iommu/amd_iommu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index f7cdd2ab7f11..8ef43224aae0 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -1636,6 +1636,12 @@ static int iommu_map_page(struct protection_domain *dom,
>  		pte[i] = __pte;
>  
>  	update_domain(dom);
> +	if (!dom->updated) {
> +		if (unlikely(amd_iommu_np_cache)) {
> +			domain_flush_pages(dom, bus_addr, page_size);
> +			domain_flush_complete(dom);
> +		}
> +	}

The two conditions can go into one if statement to make this a little
more clear.

And I'd really like to understand the unlikely - amd_iommu_np_cache
is set based on a hardware capability, so it seems rather odd to mark
it unlikely.  Dynamic branch prediction really should do the right thing
here usually.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Tom Murphy <tmurphy@arista.com>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	murphyt7@tcd.ie
Subject: Re: [PATCH] iommu/amd: flush not present cache in iommu_map_page
Date: Wed, 24 Apr 2019 07:32:46 -0700	[thread overview]
Message-ID: <20190424143246.GA24079@infradead.org> (raw)
Message-ID: <20190424143246.twDsSxCId0PzuzkeMQHUKk7KWspd0SwIDDTV2n2fx9E@z> (raw)
In-Reply-To: <20190424141900.8883-1-tmurphy@arista.com>

On Wed, Apr 24, 2019 at 03:18:59PM +0100, Tom Murphy via iommu wrote:
> check if there is a not-present cache present and flush it if there is.
> 
> Signed-off-by: Tom Murphy <tmurphy@arista.com>
> ---
>  drivers/iommu/amd_iommu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index f7cdd2ab7f11..8ef43224aae0 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -1636,6 +1636,12 @@ static int iommu_map_page(struct protection_domain *dom,
>  		pte[i] = __pte;
>  
>  	update_domain(dom);
> +	if (!dom->updated) {
> +		if (unlikely(amd_iommu_np_cache)) {
> +			domain_flush_pages(dom, bus_addr, page_size);
> +			domain_flush_complete(dom);
> +		}
> +	}

The two conditions can go into one if statement to make this a little
more clear.

And I'd really like to understand the unlikely - amd_iommu_np_cache
is set based on a hardware capability, so it seems rather odd to mark
it unlikely.  Dynamic branch prediction really should do the right thing
here usually.
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Tom Murphy <tmurphy@arista.com>
Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	murphyt7@tcd.ie
Subject: Re: [PATCH] iommu/amd: flush not present cache in iommu_map_page
Date: Wed, 24 Apr 2019 07:32:46 -0700	[thread overview]
Message-ID: <20190424143246.GA24079@infradead.org> (raw)
In-Reply-To: <20190424141900.8883-1-tmurphy@arista.com>

On Wed, Apr 24, 2019 at 03:18:59PM +0100, Tom Murphy via iommu wrote:
> check if there is a not-present cache present and flush it if there is.
> 
> Signed-off-by: Tom Murphy <tmurphy@arista.com>
> ---
>  drivers/iommu/amd_iommu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index f7cdd2ab7f11..8ef43224aae0 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -1636,6 +1636,12 @@ static int iommu_map_page(struct protection_domain *dom,
>  		pte[i] = __pte;
>  
>  	update_domain(dom);
> +	if (!dom->updated) {
> +		if (unlikely(amd_iommu_np_cache)) {
> +			domain_flush_pages(dom, bus_addr, page_size);
> +			domain_flush_complete(dom);
> +		}
> +	}

The two conditions can go into one if statement to make this a little
more clear.

And I'd really like to understand the unlikely - amd_iommu_np_cache
is set based on a hardware capability, so it seems rather odd to mark
it unlikely.  Dynamic branch prediction really should do the right thing
here usually.

  parent reply	other threads:[~2019-04-24 14:32 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-24 14:18 [PATCH] iommu/amd: flush not present cache in iommu_map_page Tom Murphy
2019-04-24 14:18 ` Tom Murphy via iommu
     [not found] ` <20190424141900.8883-1-tmurphy-nzgTgzXrdUbQT0dZR+AlfA@public.gmane.org>
2019-04-24 14:32   ` Christoph Hellwig [this message]
2019-04-24 14:32     ` Christoph Hellwig
2019-04-24 14:32     ` Christoph Hellwig
     [not found]     ` <20190424143246.GA24079-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2019-04-24 14:47       ` Tom Murphy via iommu
2019-04-24 14:47         ` Tom Murphy
2019-04-24 14:47         ` Tom Murphy via iommu
     [not found]         ` <CAPL0++7w0wR+hid=0XkGtH2wR0qvL1oNheEMQOM=8CtyhNLmag-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2019-04-24 14:58           ` Christoph Hellwig
2019-04-24 14:58             ` Christoph Hellwig
2019-04-24 14:58             ` Christoph Hellwig
2019-04-24 15:55             ` Joerg Roedel
2019-04-24 15:55               ` Joerg Roedel
2019-04-24 16:25               ` Tom Murphy
2019-04-24 16:25                 ` Tom Murphy via iommu

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