> On Apr 12, 2019, at 4:17 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Fri, Apr 12, 2019 at 12:56:33PM +0200, Peter Zijlstra wrote: >> On Thu, Apr 11, 2019 at 11:13:48PM +0200, Peter Zijlstra wrote: >>> On Thu, Apr 11, 2019 at 09:54:24PM +0200, Peter Zijlstra wrote: >>>> On Thu, Apr 11, 2019 at 09:39:06PM +0200, Peter Zijlstra wrote: >>>>> I think this bisect is bad. If you look at your own logs this patch >>>>> merely changes the failure, but doesn't make it go away. >>>>> >>>>> Before this patch (in fact, before tip/core/mm entirely) the errror >>>>> reads like the below, which suggests there is memory corruption >>>>> somewhere, and the fingered patch just makes it trigger differently. >>>>> >>>>> It would be very good to find the source of this corruption, but I'm >>>>> fairly certain it is not here. >>>> >>>> I went back to v4.20 to try and find a time when the below error did not >>>> occur, but even that reliably triggers the warning. >>> >>> So I also tested v4.19 and found that that was good, which made me >>> bisect v4.19..v4.20 >>> >>> # bad: [8fe28cb58bcb235034b64cbbb7550a8a43fd88be] Linux 4.20 >>> # good: [84df9525b0c27f3ebc2ebb1864fa62a97fdedb7d] Linux 4.19 >>> git bisect start 'v4.20' 'v4.19' >>> # bad: [ec9c166434595382be3babf266febf876327774d] Merge tag 'mips_fixes_4.20_1' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux >>> git bisect bad ec9c166434595382be3babf266febf876327774d >>> # bad: [50b825d7e87f4cff7070df6eb26390152bb29537] Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next >>> git bisect bad 50b825d7e87f4cff7070df6eb26390152bb29537 >>> # good: [99e9acd85ccbdc8f5785f9e961d4956e96bd6aa5] Merge tag 'mlx5-updates-2018-10-17' of git://git.kernel.org/pub/scm/linux/kernel/git/saeed/linux >>> git bisect good 99e9acd85ccbdc8f5785f9e961d4956e96bd6aa5 >>> # good: [c403993a41d50db1e7d9bc2d43c3c8498162312f] Merge tag 'for-linus-4.20' of https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fcminyard%2Flinux-ipmi&data=02%7C01%7Cnamit%40vmware.com%7Ca1c3ea5d4bc34cfc785508d6bf388ff3%7Cb39138ca3cee4b4aa4d6cd83d9dd62f0%7C0%7C0%7C636906647013777573&sdata=3VSR3VdE5rxOitAdkqFNPpAnAtLgDmYLzJtoUrs5v9Y%3D&reserved=0 >>> git bisect good c403993a41d50db1e7d9bc2d43c3c8498162312f >>> # good: [c05f3642f4304dd081876e77a68555b6aba4483f] Merge branch 'perf-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip >>> git bisect good c05f3642f4304dd081876e77a68555b6aba4483f >>> # bad: [44786880df196a4200c178945c4d41675faf9fb7] Merge branch 'parisc-4.20-1' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux >>> git bisect bad 44786880df196a4200c178945c4d41675faf9fb7 >>> # bad: [99792e0cea1ed733cdc8d0758677981e0cbebfed] Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip >>> git bisect bad 99792e0cea1ed733cdc8d0758677981e0cbebfed >>> # good: [fec98069fb72fb656304a3e52265e0c2fc9adf87] Merge branch 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip >>> git bisect good fec98069fb72fb656304a3e52265e0c2fc9adf87 >>> # bad: [a31acd3ee8f7dbc0370bdf4a4bfef7a8c13c7542] x86/mm: Page size aware flush_tlb_mm_range() >>> git bisect bad a31acd3ee8f7dbc0370bdf4a4bfef7a8c13c7542 >>> # good: [a7295fd53c39ce781a9792c9dd2c8747bf274160] x86/mm/cpa: Use flush_tlb_kernel_range() >>> git bisect good a7295fd53c39ce781a9792c9dd2c8747bf274160 >>> # good: [9cf38d5559e813cccdba8b44c82cc46ba48d0896] kexec: Allocate decrypted control pages for kdump if SME is enabled >>> git bisect good 9cf38d5559e813cccdba8b44c82cc46ba48d0896 >>> # good: [5b12904065798fee8b153a506ac7b72d5ebbe26c] x86/mm/doc: Clean up the x86-64 virtual memory layout descriptions >>> git bisect good 5b12904065798fee8b153a506ac7b72d5ebbe26c >>> # good: [cf089611f4c446285046fcd426d90c18f37d2905] proc/vmcore: Fix i386 build error of missing copy_oldmem_page_encrypted() >>> git bisect good cf089611f4c446285046fcd426d90c18f37d2905 >>> # good: [a5b966ae42a70b194b03eaa5eaea70d8b3790c40] Merge branch 'tlb/asm-generic' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux into x86/mm >>> git bisect good a5b966ae42a70b194b03eaa5eaea70d8b3790c40 >>> # first bad commit: [a31acd3ee8f7dbc0370bdf4a4bfef7a8c13c7542] x86/mm: Page size aware flush_tlb_mm_range() >>> >>> And 'funnily' the bad patch is one of mine too :/ >>> >>> I'll go have a look at that tomorrow, because currrently I'm way past >>> tired. >> >> OK, so the below patchlet makes it all good. It turns out that the >> provided config has: >> >> CONFIG_X86_L1_CACHE_SHIFT=7 >> >> which then, for some obscure raisin, results in flush_tlb_mm_range() >> compiling to use 320 bytes of stack: >> >> sub $0x140,%rsp >> >> Where a 'defconfig' build results in: >> >> sub $0x58,%rsp >> >> The thing that pushes it over the edge in the above fingered patch is >> the addition of a field to struct flush_tlb_info, which grows if from 32 >> to 36 bytes. >> >> So my proposal is to basically revert that, unless we can come up with >> something that GCC can't screw up. > > To clarify, 'that' is Nadav's patch: > > 515ab7c41306 ("x86/mm: Align TLB invalidation info") > > which turns out to be the real problem. Sorry for that. I still think it should be aligned, especially with all the effort the Intel puts around to avoid bus-locking on unaligned atomic operations. So the right solution seems to me as putting this data structure off stack. It would prevent flush_tlb_mm_range() from being reentrant, so we can keep a few entries for this matter and atomically increase the entry number every time we enter flush_tlb_mm_range(). But my question is - should flush_tlb_mm_range() be reentrant, or can we assume no TLB shootdowns are initiated in interrupt handlers and #MC handlers?
