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SubjectRe: [PATCH] iommu/amd: flush not present cache in iommu_map_page
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.

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