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Re: [PATCH v2 11/18] AMD/IOMMU: return old PTE from {set,clear}_iommu_pte_present()


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Fri, 10 Dec 2021 13:05:56 +0100
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  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Fri, Sep 24, 2021 at 11:51:40AM +0200, Jan Beulich wrote:
> In order to free intermediate page tables when replacing smaller
> mappings by a single larger one callers will need to know the full PTE.
> Flush indicators can be derived from this in the callers (and outside
> the locked regions). First split set_iommu_pte_present() from
> set_iommu_ptes_present(): Only the former needs to return the old PTE,
> while the latter (like also set_iommu_pde_present()) doesn't even need
> to return flush indicators. Then change return types/values and callers
> accordingly.

Without looking at further patches I would say you only care to know
whether the old PTE was present (ie: pr bit set), at which point those
functions could also return a boolean instead of a full PTE?

Thanks, Roger.



 


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