x86/mm: Fix slow_virt_to_phys() for X86_PAE again]

hi Greg,

Please apply this fix (bf70e5513dfea) on top of v4.4. v4.3 does not have the bug.
v4.5 and later has the fix already.

Thanks,

Ingo

----- Forwarded message from tip-bot for Dexuan Cui <[email protected]> -----

Date: Thu, 25 Feb 2016 10:57:39 -0800
From: tip-bot for Dexuan Cui <[email protected]>
To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected],
[email protected]
Subject: [tip:x86/urgent] x86/mm: Fix slow_virt_to_phys() for X86_PAE again

Commit-ID:  bf70e5513dfea29c3682e7eb3dbb45f0723bac09
Gitweb:     http://git.kernel.org/tip/bf70e5513dfea29c3682e7eb3dbb45f0723bac09
Author:     Dexuan Cui <[email protected]>
AuthorDate: Thu, 25 Feb 2016 01:58:12 -0800
Committer:  Thomas Gleixner <[email protected]>
CommitDate: Thu, 25 Feb 2016 19:53:15 +0100

x86/mm: Fix slow_virt_to_phys() for X86_PAE again

"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.

---
 arch/x86/mm/pageattr.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

index 2440814..9cf96d8 100644
@@ -419,24 +419,30 @@ pmd_t *lookup_pmd_address(unsigned long address)
 phys_addr_t slow_virt_to_phys(void *__virt_addr)
 {
 	unsigned long virt_addr = (unsigned long)__virt_addr;
-	unsigned long phys_addr, offset;
+	phys_addr_t phys_addr;
+	unsigned long offset;
 	enum pg_level level;
 	pte_t *pte;
 
 	pte = lookup_address(virt_addr, &level);
 	BUG_ON(!pte);
 
+	/*
+	 * 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 = pud_pfn(*(pud_t *)pte) << PAGE_SHIFT;
+		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 = pmd_pfn(*(pmd_t *)pte) << PAGE_SHIFT;
+		phys_addr = (phys_addr_t)pmd_pfn(*(pmd_t *)pte) << PAGE_SHIFT;
 		offset = virt_addr & ~PMD_PAGE_MASK;
 		break;
 	default:
-		phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
+		phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
 		offset = virt_addr & ~PAGE_MASK;
 	}
 

----- End forwarded message -----

Now queued up, thanks.

greg k-h