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x86, pageattr: fix slow_virt_to_phys() for X86_PAE

PATCH In review Dexuan Cui 1 participant 2 messages Oct 29, 2014

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Memory management x86 x86 MM
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Dexuan Cui

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#0 lore raw

PATCH 1/1 x86, pageattr: fix slow_virt_to_phys() for X86_PAE

pte_pfn() returns a PFN of long (32 bits in 32-PAE), then "long << PAGE_SHIFT" will overflow for PFNs above 4GB.

Due to this issue, some Linux 32-PAE distros, running as guests on Hyper-V, with 5GB memory assigned, can't load the netvsc driver successfully and hence the synthetic network device can't work (we can use the kernel parameter mem=3000M to work around the issue).

Cc K. Y. Srinivasan <[email protected]>
Cc Haiyang Zhang <[email protected]>
Signed-off-by Dexuan Cui <[email protected]>
---
 arch/x86/mm/pageattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/mm/pageattr.c +1 -1
index ae242a7..36de293 100644
@@ -409,7 +409,7 @@ phys_addr_t slow_virt_to_phys(void *__virt_addr)
 	psize = page_level_size(level);
 	pmask = page_level_mask(level);
 	offset = virt_addr & ~pmask;
-	phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
+	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
 	return (phys_addr | offset);
 }
 EXPORT_SYMBOL_GPL(slow_virt_to_phys);
Signature · 7 lines
1.9.1

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author
#1 lore raw
Quoted 32 lines

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Dexuan Cui
Sent: Wednesday, October 29, 2014 18:54 PM
To: [email protected]; [email protected]; linux- [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]; [email protected]
Cc: KY Srinivasan; Haiyang Zhang
Subject: [PATCH] x86, pageattr: fix slow_virt_to_phys() for X86_PAE

pte_pfn() returns a PFN of long (32 bits in 32-PAE), then "long << PAGE_SHIFT" will overflow for PFNs above 4GB.

Due to this issue, some Linux 32-PAE distros, running as guests on Hyper-V, with 5GB memory assigned, can't load the netvsc driver successfully and hence the synthetic network device can't work (we can use the kernel parameter
mem=3000M to work around the issue).

Cc K. Y. Srinivasan <[email protected]>
Cc Haiyang Zhang <[email protected]>
Signed-off-by Dexuan Cui <[email protected]>
---
 arch/x86/mm/pageattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/mm/pageattr.c +0 -0
index ae242a7..36de293 100644

arch/x86/mm/pageattr.c phys_addr_t slow_virt_to_phys(void *__virt_addr) · line 415

Quoted 8 lines
arch/x86/mm/pageattr.c +1 -1
@@ -409,7 +409,7 @@ phys_addr_t slow_virt_to_phys(void *__virt_addr)
 	psize = page_level_size(level);
 	pmask = page_level_mask(level);
 	offset = virt_addr & ~pmask;
-	phys_addr = pte_pfn(*pte) << PAGE_SHIFT;
+	phys_addr = (phys_addr_t)pte_pfn(*pte) << PAGE_SHIFT;
 	return (phys_addr | offset);
 }
 EXPORT_SYMBOL_GPL(slow_virt_to_phys);

Sorry for sending the same patch twice due to my silly typing!

Thanks,
-- Dexuan

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