drivers/gpu/drm/i915/i915_reg.h:90:shift-overflow problem ?

drivers/gpu/drm/i915/i915_reg.h:90:shift-overflow problem ?

[David Binderman]

Hello there,

drivers/gpu/drm/i915/i915_reg.h:90:28: warning: result of ‘65535 <<
20’ requires 37 bits to represent, but ‘int’ only has 32 bits
[-Wshift-overflow=]

Source code is

#define   BSM_MASK (0xFFFF << 20)

Maybe better code

#define   BSM_MASK (((unsigned long) 0xFFFF) << 20)


Regards

David Binderman
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[PATCH] drm/i915: fix BSM_MASK definition

[Jani Nikula]

The PCI config space BSM (Base of Stolen Memory) register has bits
20..31 set. The BSM_MASK definition goes beyond 32 bits, fix it.

drivers/gpu/drm/i915/i915_reg.h:90:28: warning: result of ‘65535 << 20’
requires 37 bits to represent, but ‘int’ only has 32 bits
[-Wshift-overflow=]

References: http://mid.gmane.org/CAMzoambf23FJH3Lq-gKcrVEus-bqFLxA35n0YjKGhqWOAJdBqg@mail.gmail.com
Reported-by: David Binderman <linuxdev.baldrick@gmail.com>
Cc: David Binderman <linuxdev.baldrick@gmail.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Fixes: e10fa551ae37 ("drm/i915: Clean up PCI config register handling")
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/i915_reg.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index b407411e31ba..769ac8f7ab61 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -87,7 +87,7 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
 #define   DEVEN_MCHBAR_EN (1 << 28)
 
 #define BSM 0x5c
-#define   BSM_MASK (0xFFFF << 20)
+#define   BSM_MASK (0xFFF << 20)
 
 #define HPLLCC	0xc0 /* 85x only */
 #define   GC_CLOCK_CONTROL_MASK		(0x7 << 0)
-- 
2.1.4

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Re: drivers/gpu/drm/i915/i915_reg.h:90:shift-overflow problem ?

[Chris Wilson]

On Mon, May 30, 2016 at 11:32:59AM +0100, David Binderman wrote:
> Hello there,
> 
> drivers/gpu/drm/i915/i915_reg.h:90:28: warning: result of ‘65535 <<
> 20’ requires 37 bits to represent, but ‘int’ only has 32 bits
> [-Wshift-overflow=]
> 
> Source code is
> 
> #define   BSM_MASK (0xFFFF << 20)
> 
> Maybe better code
> 
> #define   BSM_MASK (((unsigned long) 0xFFFF) << 20)

#define BSM_MASK (~0u << 20)

It should be a 32bit mask. The current (with the exception of undefined
behaviour of shifting into the signbit, fortunately gcc does what we
expect) code is functionally current as the mask will be truncated to
32bits.
-Chris

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Re: drivers/gpu/drm/i915/i915_reg.h:90:shift-overflow problem ?

[Jani Nikula]

On Mon, 30 May 2016, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> On Mon, May 30, 2016 at 11:32:59AM +0100, David Binderman wrote:
>> Hello there,
>> 
>> drivers/gpu/drm/i915/i915_reg.h:90:28: warning: result of ‘65535 <<
>> 20’ requires 37 bits to represent, but ‘int’ only has 32 bits
>> [-Wshift-overflow=]
>> 
>> Source code is
>> 
>> #define   BSM_MASK (0xFFFF << 20)
>> 
>> Maybe better code
>> 
>> #define   BSM_MASK (((unsigned long) 0xFFFF) << 20)
>
> #define BSM_MASK (~0u << 20)
>
> It should be a 32bit mask. The current (with the exception of undefined
> behaviour of shifting into the signbit, fortunately gcc does what we
> expect) code is functionally current as the mask will be truncated to
> 32bits.

In the patch I used BSM_MASK (0xFFF << 20). It does have the UB of
shifting into the sign bit, but then we have loads of e.g. (1 << 31) in
i915_reg.h which is no different.

The original code before e10fa551ae37b had ~((1<<20) - 1).

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center
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✗ Ro.CI.BAT: failure for drm/i915: fix BSM_MASK definition

[Patchwork]

== Series Details ==

Series: drm/i915: fix BSM_MASK definition
URL   : https://patchwork.freedesktop.org/series/7982/
State : failure

== Summary ==

Series 7982v1 drm/i915: fix BSM_MASK definition
http://patchwork.freedesktop.org/api/1.0/series/7982/revisions/1/mbox

Test gem_close_race:
        Subgroup basic-process:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
Test gem_exec_basic:
        Subgroup basic-render:
                pass       -> DMESG-WARN (ro-ivb2-i7-3770)
        Subgroup readonly-render:
                dmesg-warn -> PASS       (ro-ivb2-i7-3770)
Test gem_exec_flush:
        Subgroup basic-uc-ro-default:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
        Subgroup basic-wb-prw-default:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
Test gem_exec_store:
        Subgroup basic-blt:
                dmesg-warn -> PASS       (ro-ivb2-i7-3770)
        Subgroup basic-default:
                dmesg-warn -> PASS       (ro-ivb2-i7-3770)
Test gem_mmap_gtt:
        Subgroup basic-small-copy:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup basic-write-no-prefault:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
Test gem_pwrite:
        Subgroup basic:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
Test gem_storedw_loop:
        Subgroup basic-bsd:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup basic-render:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
Test kms_addfb_basic:
        Subgroup addfb25-framebuffer-vs-set-tiling:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup addfb25-x-tiled:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup addfb25-y-tiled-small:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup bad-pitch-1024:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup bad-pitch-63:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup framebuffer-vs-set-tiling:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
        Subgroup too-high:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup too-wide:
                dmesg-warn -> PASS       (ro-skl-i7-6700hq)
        Subgroup unused-offsets:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
Test kms_force_connector_basic:
        Subgroup force-edid:
                pass       -> DMESG-WARN (ro-ivb2-i7-3770)
Test kms_pipe_crc_basic:
        Subgroup suspend-read-crc-pipe-b:
                pass       -> INCOMPLETE (fi-hsw-i7-4770k)
Test kms_setmode:
        Subgroup basic-clone-single-crtc:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)
Test kms_sink_crc_basic:
                pass       -> DMESG-WARN (ro-skl-i7-6700hq)

fi-bdw-i7-5557u  total:102  pass:93   dwarn:0   dfail:0   fail:0   skip:8  
fi-hsw-i7-4770k  total:190  pass:172  dwarn:0   dfail:0   fail:0   skip:17 
fi-hsw-i7-4770r  total:209  pass:186  dwarn:0   dfail:0   fail:0   skip:23 
fi-skl-i7-6700k  total:209  pass:184  dwarn:0   dfail:0   fail:0   skip:25 
fi-snb-i7-2600   total:209  pass:170  dwarn:0   dfail:0   fail:0   skip:39 
ro-bdw-i5-5250u  total:102  pass:93   dwarn:0   dfail:0   fail:0   skip:8  
ro-bsw-n3050     total:209  pass:168  dwarn:0   dfail:0   fail:2   skip:39 
ro-byt-n2820     total:209  pass:169  dwarn:0   dfail:0   fail:3   skip:37 
ro-hsw-i3-4010u  total:209  pass:186  dwarn:0   dfail:0   fail:0   skip:23 
ro-hsw-i7-4770r  total:102  pass:82   dwarn:0   dfail:0   fail:0   skip:19 
ro-ilk-i7-620lm  total:1    pass:0    dwarn:0   dfail:0   fail:0   skip:0  
ro-ilk1-i5-650   total:204  pass:146  dwarn:0   dfail:0   fail:1   skip:57 
ro-ivb-i7-3770   total:102  pass:75   dwarn:0   dfail:0   fail:0   skip:26 
ro-ivb2-i7-3770  total:102  pass:46   dwarn:33  dfail:0   fail:0   skip:22 
ro-skl-i7-6700hq total:204  pass:172  dwarn:11  dfail:0   fail:0   skip:21 
ro-snb-i7-2620M  total:102  pass:72   dwarn:0   dfail:0   fail:0   skip:29 
fi-bsw-n3050 failed to connect after reboot
fi-byt-n2820 failed to connect after reboot
ro-bdw-i7-5557U failed to connect after reboot
ro-bdw-i7-5600u failed to connect after reboot

Results at /archive/results/CI_IGT_test/RO_Patchwork_1053/

031f2bb drm-intel-nightly: 2016y-05m-30d-17h-51m-33s UTC integration manifest
8832bc7 drm/i915: fix BSM_MASK definition

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