[PATCH v5sub1 2/8] arm64: add support for ioremap() block mappings

On Mon, Feb 01, 2016 at 02:10:04PM +0000, Mark Rutland wrote:

On Mon, Feb 01, 2016 at 11:54:47AM +0100, Ard Biesheuvel wrote:

quoted

This wires up the existing generic huge-vmap feature, which allows
ioremap() to use PMD or PUD sized block mappings. It also adds support
to the unmap path for dealing with block mappings, which will allow us
to unmap the __init region using unmap_kernel_range() in a subsequent
patch.

Signed-off-by: Ard Biesheuvel <redacted>

Reviewed-by: Mark Rutland <mark.rutland@arm.com>

I was a little bit worried about this potentially not matching the
granularity we used when creating mappings, but seeing how
p?d_clear_huge are called by unmap_kernel_range, I think this is fine.

I tried the warnings below and they didn't trigger. Anyway, if we ever
unmapped more, I guess we would have quickly triggered a kernel fault.

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index fb42a5bffe47..40362d62d1e1 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c

@@ -77,8 +77,10 @@ static void vunmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end)
 	pmd = pmd_offset(pud, addr);
 	do {
 		next = pmd_addr_end(addr, end);
-		if (pmd_clear_huge(pmd))
+		if (pmd_clear_huge(pmd)) {
+			WARN_ON(next < addr + PMD_SIZE);
 			continue;
+		}
 		if (pmd_none_or_clear_bad(pmd))
 			continue;
 		vunmap_pte_range(pmd, addr, next);

@@ -93,8 +95,10 @@ static void vunmap_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end)
 	pud = pud_offset(pgd, addr);
 	do {
 		next = pud_addr_end(addr, end);
-		if (pud_clear_huge(pud))
+		if (pud_clear_huge(pud)) {
+			WARN_ON(next < addr + PUD_SIZE);
 			continue;
+		}
 		if (pud_none_or_clear_bad(pud))
 			continue;
 		vunmap_pmd_range(pud, addr, next);

-- 
Catalin