------------------------------ On Mon, Feb 10, 2014 10:50 PM GMT Larry Finger wrote: >On 02/10/2014 03:38 PM, Stanislaw Gruszka wrote: >> This patch fixes regression caused by commit a16dad77634 "MIPS: Fix >> potencial corruption". That commit fixes one corruption scenario in >> cost of adding another one, which actually start to cause crashes >> on Yeeloong laptop when rtl8187 driver is used. >> >> For correct DMA read operation on machines without DMA coherence, kernel >> have to invalidate cache, such it will refill later with new data that >> device wrote to memory, when that data is needed to process. We can only >> invalidate full cache line. Hence when cache line includes both dma >> buffer and some other data (written in cache, but not yet in main >> memory), the other data can not hit memory due to invalidation. That >> happen on rtl8187 where struct rtl8187_priv fields are located just >> before and after small buffers that are passed to USB layer and DMA >> is performed on them. >> >> To fix the problem we align buffers and reserve space after them to make >> them match cache line. >> >> This patch does not resolve all possible MIPS problems entirely, for >> that we have to assure that we always map cache aligned buffers for DMA, >> what can be complex or even not possible. But patch fixes visible and >> reproducible regression and seems other possible corruptions do not >> happen in practice, since Yeeloong laptop works stable without rtl8187 >> driver. >> >> Bug report: >> https://bugzilla.kernel.org/show_bug.cgi?id=54391 >> >> Reported-by: Petr Pisar <petr.pisar@xxxxxxxx> >> Bisected-by: Tom Li <biergaizi2009@xxxxxxxxx> >> Reported-and-tested-by: Tom Li <biergaizi2009@xxxxxxxxx> >> Cc: stable@xxxxxxxxxxxxxxx >> Signed-off-by: Stanislaw Gruszka <stf_xl@xxxxx> >> --- > >Congratulations to all for sorting this out. It could not have been too easy. > >The only effect I see on architectures with DMA coherence is that the private >data area has grown a little. Certainly, my RTL8187B device still works on x86_64. > >Acked-by: Larry Finger <Larry.Finger@xxxxxxxxxxxxx> > >Larry > >> drivers/net/wireless/rtl818x/rtl8187/rtl8187.h | 10 ++++++++-- >> 1 files changed, 8 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h b/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h >> index 56aee06..a6ad79f 100644 >> --- a/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h >> +++ b/drivers/net/wireless/rtl818x/rtl8187/rtl8187.h >> @@ -15,6 +15,8 @@ >> #ifndef RTL8187_H >> #define RTL8187_H >> >> +#include <linux/cache.h> >> + >> #include "rtl818x.h" >> #include "leds.h" >> >> @@ -139,7 +141,10 @@ struct rtl8187_priv { >> u8 aifsn[4]; >> u8 rfkill_mask; >> struct { >> - __le64 buf; >> + union { >> + __le64 buf; >> + u8 dummy1[L1_CACHE_BYTES]; >> + } ____cacheline_aligned; >> struct sk_buff_head queue; >> } b_tx_status; /* This queue is used by both -b and non-b devices */ >> struct mutex io_mutex; >> @@ -147,7 +152,8 @@ struct rtl8187_priv { >> u8 bits8; >> __le16 bits16; >> __le32 bits32; >> - } *io_dmabuf; >> + u8 dummy2[L1_CACHE_BYTES]; >> + } *io_dmabuf ____cacheline_aligned; >> bool rfkill_off; >> u16 seqno; >> }; >> >
