[SRU][Wily][PATCH 1/1] x86/mm: Fix slow_virt_to_phys() for X86_PAE again

[Joseph Salisbury]

From: Dexuan Cui <decui at microsoft.com>

BugLink: http://bugs.launchpad.net/bugs/1549601

"d1cd12108346: x86, pageattr: Prevent overflow in slow_virt_to_phys() for
X86_PAE" was unintentionally removed by the recent "34437e67a672: x86/mm: Fix
slow_virt_to_phys() to handle large PAT bit".

And, the variable 'phys_addr' was defined as "unsigned long" by mistake -- it should
be "phys_addr_t".

As a result, Hyper-V network driver in 32-PAE Linux guest can't work again.

Fixes: commit 34437e67a672: "x86/mm: Fix slow_virt_to_phys() to handle large PAT bit"
Signed-off-by: Dexuan Cui <decui at microsoft.com>
Reviewed-by: Toshi Kani <toshi.kani at hpe.com>
Cc: olaf at aepfle.de
Cc: gregkh at linuxfoundation.org
Cc: jasowang at redhat.com
Cc: driverdev-devel at linuxdriverproject.org
Cc: linux-mm at kvack.org
Cc: apw at canonical.com
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: K. Y. Srinivasan <kys at microsoft.com>
Cc: Haiyang Zhang <haiyangz at microsoft.com>
Link: http://lkml.kernel.org/r/1456394292-9030-1-git-send-email-decui@microsoft.com
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
(backported from commit bf70e5513dfea29c3682e7eb3dbb45f0723bac09)
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 arch/x86/include/asm/page_types.h |  6 ++++++
 arch/x86/mm/pageattr.c            | 25 +++++++++++++++++++++----
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
index c7c712f..d825589 100644
--- a/arch/x86/include/asm/page_types.h
+++ b/arch/x86/include/asm/page_types.h
@@ -9,6 +9,12 @@
 #define PAGE_SIZE	(_AC(1,UL) << PAGE_SHIFT)
 #define PAGE_MASK	(~(PAGE_SIZE-1))
 
+#define PMD_PAGE_SIZE		(_AC(1, UL) << PMD_SHIFT)
+#define PMD_PAGE_MASK		(~(PMD_PAGE_SIZE-1))
+
+#define PUD_PAGE_SIZE           (_AC(1, UL) << PUD_SHIFT)
+#define PUD_PAGE_MASK           (~(PUD_PAGE_SIZE-1))
+
 #define __PHYSICAL_MASK		((phys_addr_t)((1ULL << __PHYSICAL_MASK_SHIFT) - 1))
 #define __VIRTUAL_MASK		((1UL << __VIRTUAL_MASK_SHIFT) - 1)
 
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 727158c..2e5c533 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -423,10 +423,27 @@ phys_addr_t slow_virt_to_phys(void *__virt_addr)
 
 	pte = lookup_address(virt_addr, &level);
 	BUG_ON(!pte);
-	pmask = page_level_mask(level);
-	offset = virt_addr & ~pmask;
-	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
-	return (phys_addr | offset);
+
+	/*
+	 * pXX_pfn() returns unsigned long, which must be cast to phys_addr_t
+	 * before being left-shifted PAGE_SHIFT bits -- this trick is to
+	 * make 32-PAE kernel work correctly.
+	 */
+	switch (level) {
+	case PG_LEVEL_1G:
+		phys_addr = (phys_addr_t)pud_pfn(*(pud_t *)pte) << PAGE_SHIFT;
+		offset = virt_addr & ~PUD_PAGE_MASK;
+		break;
+	case PG_LEVEL_2M:
+		phys_addr = (phys_addr_t)pmd_pfn(*(pmd_t *)pte) << PAGE_SHIFT;
+		offset = virt_addr & ~PMD_PAGE_MASK;
+		break;
+	default:
+		phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
+		offset = virt_addr & ~PAGE_MASK;
+	}
+
+	return (phys_addr_t)(phys_addr | offset);
 }
 EXPORT_SYMBOL_GPL(slow_virt_to_phys);
 
-- 
1.9.1