[PATCH] x86/mmcfg: Fix initalisation of variables in pci_mmcfg_nvidia_mcp55()

[PATCH] x86/mmcfg: Fix initalisation of variables in pci_mmcfg_nvidia_mcp55()

[Andrew Cooper]

Shifting into the sign bit of an integer is undefined behaviour.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>

I was experimenting with -fsanitise=undefined and this bit failed to compile,
as the initialisation became a non-constant expression.
---
 xen/arch/x86/x86_64/mmconfig-shared.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/x86_64/mmconfig-shared.c b/xen/arch/x86/x86_64/mmconfig-shared.c
index 742bc18..a7592c6 100644
--- a/xen/arch/x86/x86_64/mmconfig-shared.c
+++ b/xen/arch/x86/x86_64/mmconfig-shared.c
@@ -182,10 +182,10 @@ static const char __init *pci_mmcfg_nvidia_mcp55(void)
     int bus, i;
 
     static const u32 extcfg_regnum      = 0x90;
-    static const u32 extcfg_enable_mask = 1<<31;
-    static const u32 extcfg_start_mask  = 0xff<<16;
+    static const u32 extcfg_enable_mask = 1u << 31;
+    static const u32 extcfg_start_mask  = 0xffu << 16;
     static const int extcfg_start_shift = 16;
-    static const u32 extcfg_size_mask   = 0x3<<28;
+    static const u32 extcfg_size_mask   = 3u << 28;
     static const int extcfg_size_shift  = 28;
     static const int extcfg_sizebus[]   = {0xff, 0x7f, 0x3f, 0x1f};
     static const u32 extcfg_base_mask[] = {0x7ff8, 0x7ffc, 0x7ffe, 0x7fff};
-- 
2.1.4


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Re: [PATCH] x86/mmcfg: Fix initalisation of variables in pci_mmcfg_nvidia_mcp55()

[Jan Beulich]

>>> On 03.08.16 at 11:51, <andrew.cooper3@citrix.com> wrote:
> --- a/xen/arch/x86/x86_64/mmconfig-shared.c
> +++ b/xen/arch/x86/x86_64/mmconfig-shared.c
> @@ -182,10 +182,10 @@ static const char __init *pci_mmcfg_nvidia_mcp55(void)
>      int bus, i;
>  
>      static const u32 extcfg_regnum      = 0x90;
> -    static const u32 extcfg_enable_mask = 1<<31;
> -    static const u32 extcfg_start_mask  = 0xff<<16;
> +    static const u32 extcfg_enable_mask = 1u << 31;

Aiui only this one change is really related to the patch subject; the
other two I suppose you just alter for consistency? Anyway,
Acked-by: Jan Beulich <jbeulich@suse.com>

> +    static const u32 extcfg_start_mask  = 0xffu << 16;
>      static const int extcfg_start_shift = 16;
> -    static const u32 extcfg_size_mask   = 0x3<<28;
> +    static const u32 extcfg_size_mask   = 3u << 28;
>      static const int extcfg_size_shift  = 28;
>      static const int extcfg_sizebus[]   = {0xff, 0x7f, 0x3f, 0x1f};
>      static const u32 extcfg_base_mask[] = {0x7ff8, 0x7ffc, 0x7ffe, 0x7fff};
> -- 
> 2.1.4




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Re: [PATCH] x86/mmcfg: Fix initalisation of variables in pci_mmcfg_nvidia_mcp55()

[Andrew Cooper]

On 03/08/16 11:24, Jan Beulich wrote:
>>>> On 03.08.16 at 11:51, <andrew.cooper3@citrix.com> wrote:
>> --- a/xen/arch/x86/x86_64/mmconfig-shared.c
>> +++ b/xen/arch/x86/x86_64/mmconfig-shared.c
>> @@ -182,10 +182,10 @@ static const char __init *pci_mmcfg_nvidia_mcp55(void)
>>      int bus, i;
>>  
>>      static const u32 extcfg_regnum      = 0x90;
>> -    static const u32 extcfg_enable_mask = 1<<31;
>> -    static const u32 extcfg_start_mask  = 0xff<<16;
>> +    static const u32 extcfg_enable_mask = 1u << 31;
> Aiui only this one change is really related to the patch subject; the
> other two I suppose you just alter for consistency? Anyway,
> Acked-by: Jan Beulich <jbeulich@suse.com>

Indeed.

~Andrew

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