On 2020-09-01 16:02, Greg KH wrote: > On Fri, Aug 28, 2020 at 12:03:38PM +0200, Bodo Stroesser wrote: >> Hi, >> I'm adding stable@xxxxxxxxxxxxxxx >> >> Once again, this time really adding stable. >> >> On 2020-06-03 04:31, Martin K. Petersen wrote: >>> On Thu, 28 May 2020 21:31:08 +0200, Bodo Stroesser wrote: >>> >>>> 1) If remaining ring space before the end of the ring is >>>> smaller then the next cmd to write, tcmu writes a padding >>>> entry which fills the remaining space at the end of the >>>> ring. >>>> Then tcmu calls tcmu_flush_dcache_range() with the size >>>> of struct tcmu_cmd_entry as data length to flush. >>>> If the space filled by the padding was smaller then >>>> tcmu_cmd_entry, tcmu_flush_dcache_range() is called for >>>> an address range reaching behind the end of the vmalloc'ed >>>> ring. >>>> tcmu_flush_dcache_range() in a loop calls >>>> flush_dcache_page(virt_to_page(start)); >>>> for every page being part of the range. On x86 the line is >>>> optimized out by the compiler, as flush_dcache_page() is >>>> empty on x86. >>>> But I assume the above can cause trouble on other >>>> architectures that really have a flush_dcache_page(). >>>> For paddings only the header part of an entry is relevant >>>> Due to alignment rules the header always fits in the >>>> remaining space, if padding is needed. >>>> So tcmu_flush_dcache_range() can safely be called with >>>> sizeof(entry->hdr) as the length here. >>>> >>>> [...] >>> >>> Applied to 5.8/scsi-queue, thanks! >>> >>> [1/1] scsi: target: tcmu: Fix size in calls to tcmu_flush_dcache_range >>> https://git.kernel.org/mkp/scsi/c/8c4e0f212398 >>> >> >> The full commit of this patch is: >> 8c4e0f212398cdd1eb4310a5981d06a723cdd24f >> >> This patch is the first of four patches that are necessary to run tcmu >> on ARM without crash. For details please see >> https://bugzilla.kernel.org/show_bug.cgi?id=208045 >> Upsteam commits of patches 2,3, and 4 are: >> 2: 3c58f737231e "scsi: target: tcmu: Optimize use of flush_dcache_page" >> 3: 3145550a7f8b "scsi: target: tcmu: Fix crash in tcmu_flush_dcache_range >> on ARM" >> 4: 5a0c256d96f0 "scsi: target: tcmu: Fix crash on ARM during cmd >> completion" >> >> Since patches 3 and 4 already were accepted for 5.8, 5.4, and 4.19, and >> I sent a request to add patch 2 about 1 hour ago, please consider adding >> this patch to 5.4 and 4.19, because without it tcmu on ARM will still >> crash. > > I don't see such a request, and am confused now. > > What exact commits do you want backported, and to what trees? > > thanks, > > greg k-h > Sorry for the confusion. The subject of the request I mentioned is "Re: [PATCH v2 0/2] scsi: target: tcmu: fix crashes on ARM" because it is for the first patch of a small series of two. Please backport to kernels 4.19 and 5.4 (it is part of 5.8 from beginning): 8c4e0f212398 "scsi: target: tcmu: fix size in calls to tcmu_flush_dcache_range" Please backport to kernels 4.19, 5.4 and 5.8: 3c58f737231e "scsi: target: tcmu: Optimize use of flush_dcache_page" Backporting to 4.14 or earlier AFAICS would need more work, especially testing. I don't think that its worth it. Thank you, Bodo
