2014-10-29 09:46:25

by Dexuan Cui

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(-)

diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index ae242a7..36de293 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -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);
--
1.9.1

2014-10-29 10:07:06

by Dexuan Cui

Subject: RE: [PATCH] x86, pageattr: fix slow_virt_to_phys() for X86_PAE

> -----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(-)
>
> diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
> index ae242a7..36de293 100644
> --- a/arch/x86/mm/pageattr.c
> +++ b/arch/x86/mm/pageattr.c
> @@ -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