[PATCH v2 2/4] ioremap: Implement TLB_INV before huge mapping

[Chintan Pandya]

Huge mapping changes PMD/PUD which could have
valid previous entries. This requires proper
TLB maintanance on some architectures, like
ARM64.

Implent BBM (break-before-make) safe TLB
invalidation.

Here, I've used flush_tlb_pgtable() instead
of flush_kernel_range() because invalidating
intermediate page_table entries could have
been optimized for specific arch. That's the
case with ARM64 at least.

Signed-off-by: Chintan Pandya <cpandya at codeaurora.org>
---
 lib/ioremap.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/lib/ioremap.c b/lib/ioremap.c
index 54e5bba..55f8648 100644
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -13,6 +13,7 @@
 #include <linux/export.h>
 #include <asm/cacheflush.h>
 #include <asm/pgtable.h>
+#include <asm-generic/tlb.h>
 
 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
 static int __read_mostly ioremap_p4d_capable;
@@ -80,6 +81,7 @@ static inline int ioremap_pmd_range(pud_t *pud, unsigned long addr,
 		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
 {
 	pmd_t *pmd;
+	pmd_t old_pmd;
 	unsigned long next;
 
 	phys_addr -= addr;
@@ -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);
 		}
 
 		if (ioremap_pte_range(pmd, addr, next, phys_addr + addr, prot))
@@ -107,6 +114,7 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr,
 		unsigned long end, phys_addr_t phys_addr, pgprot_t prot)
 {
 	pud_t *pud;
+	pud_t old_pud;
 	unsigned long next;
 
 	phys_addr -= addr;
@@ -118,10 +126,15 @@ static inline int ioremap_pud_range(p4d_t *p4d, unsigned long addr,
 
 		if (ioremap_pud_enabled() &&
 		    ((next - addr) == PUD_SIZE) &&
-		    IS_ALIGNED(phys_addr + addr, PUD_SIZE) &&
-		    pud_free_pmd_page(pud)) {
-			if (pud_set_huge(pud, phys_addr + addr, prot))
+		    IS_ALIGNED(phys_addr + addr, PUD_SIZE)) {
+			old_pud = *pud;
+			pud_clear(pud);
+			flush_tlb_pgtable(&init_mm, addr);
+			if (pud_set_huge(pud, phys_addr + addr, prot)) {
+				pud_free_pmd_page(&old_pud);
 				continue;
+			} else
+				set_pud(pud, old_pud);
 		}
 
 		if (ioremap_pmd_range(pud, addr, next, phys_addr + addr, prot))
-- 
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