[Qemu-devel] [PATCH v3 2/9] target-arm: Add computation of starting level for S2 PTW

[Edgar E. Iglesias]

From: "Edgar E. Iglesias" <address@hidden>

The starting level for S2 pagetable walks is computed
differently from the S1 starting level. Implement the S2
variant.

Signed-off-by: Edgar E. Iglesias <address@hidden>
---
 target-arm/helper.c | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 5a5e5f0..507324f 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -6549,18 +6549,33 @@ static bool get_phys_addr_lpae(CPUARMState *env, 
target_ulong address,
         goto do_fault;
     }
 
-    /* The starting level depends on the virtual address size (which can be
-     * up to 48 bits) and the translation granule size. It indicates the number
-     * of strides (granule_sz bits at a time) needed to consume the bits
-     * of the input address. In the pseudocode this is:
-     *  level = 4 - RoundUp((inputsize - grainsize) / stride)
-     * where their 'inputsize' is our 'va_size - tsz', 'grainsize' is
-     * our 'granule_sz + 3' and 'stride' is our 'granule_sz'.
-     * Applying the usual "rounded up m/n is (m+n-1)/n" and simplifying:
-     *     = 4 - (va_size - tsz - granule_sz - 3 + granule_sz - 1) / granule_sz
-     *     = 4 - (va_size - tsz - 4) / granule_sz;
-     */
-    level = 4 - (va_size - tsz - 4) / granule_sz;
+    if (mmu_idx != ARMMMUIdx_S2NS) {
+        /* The starting level depends on the virtual address size (which can
+         * be up to 48 bits) and the translation granule size. It indicates
+         * the number of strides (granule_sz bits at a time) needed to
+         * consume the bits of the input address. In the pseudocode this is:
+         *  level = 4 - RoundUp((inputsize - grainsize) / stride)
+         * where their 'inputsize' is our 'va_size - tsz', 'grainsize' is
+         * our 'granule_sz + 3' and 'stride' is our 'granule_sz'.
+         * Applying the usual "rounded up m/n is (m+n-1)/n" and simplifying:
+         * = 4 - (va_size - tsz - granule_sz - 3 + granule_sz - 1) / granule_sz
+         * = 4 - (va_size - tsz - 4) / granule_sz;
+         */
+        level = 4 - (va_size - tsz - 4) / granule_sz;
+    } else {
+        unsigned int startlevel = extract32(tcr->raw_tcr, 6, 2);
+
+        /* For stage 2 translations the starting level is specified by the
+         * VCTR_EL2.SL0 field (whose interpretation depends on the page size)
+         */
+        if (granule_sz == 9) {
+            /* 4K pages */
+            level = 2 - startlevel;
+        } else {
+            /* 16K or 64K pages */
+            level = 3 - startlevel;
+        }
+    }
 
     /* Clear the vaddr bits which aren't part of the within-region address,
      * so that we don't have to special case things when calculating the
-- 
1.9.1