iommu/amd: Introduce first_pte_l7() helper

Given an arbitrary pte that is part of a large mapping, this function
returns the first pte of the series (and optionally the mapped size and
number of PTEs)
It will be re-used in a subsequent patch to replace an existing L7
mapping.

Fixes: 6d568ef9a622 ("iommu/amd: Allow downgrading page-sizes in alloc_pte()")
Signed-off-by: Andrei Dulea <adulea@amazon.de>

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index c7e28a8..a227e7a 100644 (file)
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -501,6 +501,29 @@ static void iommu_uninit_device(struct device *dev)
         */
 }
 
+/*
+ * Helper function to get the first pte of a large mapping
+ */
+static u64 *first_pte_l7(u64 *pte, unsigned long *page_size,
+                        unsigned long *count)
+{
+       unsigned long pte_mask, pg_size, cnt;
+       u64 *fpte;
+
+       pg_size  = PTE_PAGE_SIZE(*pte);
+       cnt      = PAGE_SIZE_PTE_COUNT(pg_size);
+       pte_mask = ~((cnt << 3) - 1);
+       fpte     = (u64 *)(((unsigned long)pte) & pte_mask);
+
+       if (page_size)
+               *page_size = pg_size;
+
+       if (count)
+               *count = cnt;
+
+       return fpte;
+}
+
 /****************************************************************************
  *
  * Interrupt handling functions
@@ -1567,17 +1590,12 @@ static u64 *fetch_pte(struct protection_domain *domain,
                *page_size = PTE_LEVEL_PAGE_SIZE(level);
        }
 
-       if (PM_PTE_LEVEL(*pte) == 0x07) {
-               unsigned long pte_mask;
-
-               /*
-                * If we have a series of large PTEs, make
-                * sure to return a pointer to the first one.
-                */
-               *page_size = pte_mask = PTE_PAGE_SIZE(*pte);
-               pte_mask   = ~((PAGE_SIZE_PTE_COUNT(pte_mask) << 3) - 1);
-               pte        = (u64 *)(((unsigned long)pte) & pte_mask);
-       }
+       /*
+        * If we have a series of large PTEs, make
+        * sure to return a pointer to the first one.
+        */
+       if (PM_PTE_LEVEL(*pte) == PAGE_MODE_7_LEVEL)
+               pte = first_pte_l7(pte, page_size, NULL);
 
        return pte;
 }