Messages in this thread | | | Subject | Re: [PATCH] uio: Fix bus error that access memory mapped by physical | From | wubian <> | Date | Wed, 23 Jun 2021 20:32:55 +0800 |
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On 2021/6/23 下午5:25, Greg KH wrote: > A: Because it messes up the order in which people normally read text. > Q: Why is top-posting such a bad thing? > A: Top-posting. > Q: What is the most annoying thing in e-mail? > > A: No. > Q: Should I include quotations after my reply? > > http://daringfireball.net/2007/07/on_top > > On Wed, Jun 23, 2021 at 04:49:16PM +0800, wubian wrote: >> First,thanks for your reply >> >> I haven’t found this problem on the x86 platform. I only found it on arm64. >> I used gdb to track memset and found that the bus error in >> glibc/sysdeps/aarch64/memset.S: dc zva, dst; reference "Architecture >> Reference ManualArmv8, for Armv8-A architecture profile" manual found that >> the dc assembly instruction(performance optimization) is related to the >> operation of the cache, that is to say, there is a bus error in the >> operation of the cache, and then check the "ARM Cortex-A Series Programmer's >> Guide for ARMv8-A " manual, found that the armv8 architecture cache has data >> cache and write buffer, and there are two operation modes write-back and >> write-through, write operations in these two modes, the data flow will pass >> through the write buffer, and pgprot_noncached will prohibit data Cache and >> write buffer, this causes the dc command in memset to fail (bus error), and >> pgprot_writecombine does not prohibit write buffer, so the dc command in >> memset is successfully operated when pgprot_writecombine is used. > > Are you sure this is not just a specific hardware platform issue? Are > you sure this is going to be correct for _ALL_ arm64 systems? > > Perhaps get the arm64 developers to agree with what is happening here as > this is the first time anyone has reported this problem. > > What specific platform are you using that this issue happens on? > > thanks, > > greg k-h > >
I apologize for the kernel mail reply format problem, I will pay attention to it in the future.
I only found this problem on Huawei Kunpeng 920 cpu at present, and found that some people have raised similar problems on the Internet. link:https://github.com/ikwzm/udmabuf/issues/31
@Catalin Marinas @Will Deacon Has anyone reported a similar problem on the arm64 platform?
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