On 3/15/2018 7:01 PM, Mark Rutland wrote:

On Thu, Mar 15, 2018 at 06:15:04PM +0530, Chintan Pandya wrote:

quoted

@@ -91,10 +93,15 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
  
  		if (ioremap_pmd_enabled() &&
  		    ((next - addr) == PMD_SIZE) &&
-		    IS_ALIGNED(phys_addr + addr, PMD_SIZE) &&
-		    pmd_free_pte_page(pmd)) {
-			if (pmd_set_huge(pmd, phys_addr + addr, prot))
+		    IS_ALIGNED(phys_addr + addr, PMD_SIZE)) {
+			old_pmd = *pmd;
+			pmd_clear(pmd);
+			flush_tlb_pgtable(&init_mm, addr);
+			if (pmd_set_huge(pmd, phys_addr + addr, prot)) {
+				pmd_free_pte_page(&old_pmd);
  				continue;
+			} else
+				set_pmd(pmd, old_pmd);
  		}
  

Can we have something like a pmd_can_set_huge() helper? Then we could
avoid pointless modification and TLB invalidation work when
pmd_set_huge() will fail.

Actually, pmd_set_huge() will never fail because, if
CONFIG_HAVE_ARCH_HUGE_VMAP is disabled, ioremap_pmd_enabled()
will fail and if enabled (i.e. ARM64 & x86), they don't fail
in their implementation. So, rather we can do the following.

-                       if (pmd_set_huge(pmd, phys_addr + addr, prot)) {
-                               pmd_free_pte_page(&old_pmd);
-                               continue;
-                       } else
-                               set_pmd(pmd, old_pmd);
+                       pmd_set_huge(pmd, phys_addr + addr, prot)
+                       pmd_free_pte_page(&old_pmd);
+                       continue;

	if (ioremap_pmd_enabled() &&
	    ((next - addr) == PMD_SIZE) &&
	    IS_ALIGNED(phys_addr + addr, PMD_SIZE) &&
	    pmd_can_set_huge(pmd, phys_addr + addr, prot)) {
	    	// clear entries, invalidate TLBs, and free tables
		...
		continue;

	}

Thanks,
MArk.

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Chintan
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