Messages in this thread Patch in this message | | | Date | Sat, 16 Nov 2019 12:32:44 +0000 | From | Marc Zyngier <> | Subject | Re: rmk/for-next bisection: boot on ox820-cloudengines-pogoplug-series-3 |
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On Sat, 16 Nov 2019 10:26:27 +0000 Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> (+ Arnd) > > On Sat, 16 Nov 2019 at 05:54, kernelci.org bot <bot@kernelci.org> wrote: > > > > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * > > * This automated bisection report was sent to you on the basis * > > * that you may be involved with the breaking commit it has * > > * found. No manual investigation has been done to verify it, * > > * and the root cause of the problem may be somewhere else. * > > * * > > * If you do send a fix, please include this trailer: * > > * Reported-by: "kernelci.org bot" <bot@kernelci.org> * > > * * > > * Hope this helps! * > > * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * > > > > rmk/for-next bisection: boot on ox820-cloudengines-pogoplug-series-3 > > > > Summary: > > Start: b6c3c42cfda0 ARM: 8938/1: kernel: initialize broadcast hrtimer based clock event device > > Details: https://kernelci.org/boot/id/5dcf3f0359b514dc84cf54c8 > > Plain log: https://storage.kernelci.org//rmk/for-next/v5.4-rc5-26-gb6c3c42cfda0/arm/oxnas_v6_defconfig/gcc-8/lab-baylibre/boot-ox820-cloudengines-pogoplug-series-3.txt > > HTML log: https://storage.kernelci.org//rmk/for-next/v5.4-rc5-26-gb6c3c42cfda0/arm/oxnas_v6_defconfig/gcc-8/lab-baylibre/boot-ox820-cloudengines-pogoplug-series-3.html > > Result: ea70bf6e92c5 ARM: 8935/1: decompressor: avoid CP15 barrier instructions in v7 cache setup code > > > > OK, so this regression is caused by the fact that the 'armv7' cache > maintenance routines in the decompressor are also used for ARMv6 cores > if they implement the CPUID extension, which I failed to realise when > I sent this patch.
Nobody expects the 11MPcore... :-(.
> There are roughly three ways to deal with this: > 1) add a mask/val match pair for ARM11MPcore and ARM1176 that hardwire > them to the ARMv6 routines, even though they implement the CPUID > extension. This would be very easy, but assumes that those two cores > are the only ones that are affected by this. > 2) modify the v7 routines to check for the L1Hvd MMFR1 attribute (in > the flush routine) and for the CP15BEN SCTLR bit (in the on/off > routines), and jump to the respective v6 variants if the CPU turns out > not to support the v7 one. > 3) revert the patch, and just enable the CP15 barriers (and issue a v7 > barrier) in the v7 on() and flush() routines. > > I am leaning towards the latter, since it is the most straightforward, > even though it mixes v7 and cp15 barriers in the same function, but > that was mostly a cosmetic concern anyway.
A potential alternative is to check for the presence of architected barriers in a macro (see the hack below). I've given it a go as a 32bit guest on an A72 box, both as ARM and Thumb, and nothing caught fire. Of course, it remains to be seen whether it works on a v6 machine (I don't think I have any left in my zoo -- please don't send me any), and more importantly whether we want to carry this kind of horror...
M.
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index ec14687aea3c..144de4b08547 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -656,19 +656,40 @@ params: ldr r0, =0x10000100 @ params_phys for RPC .align #endif - .macro v7dsb + @ Check for architected barrier instructions + @ Branch to the tgt label if v7 barriers are + @ not available. Corrupts the tmp register + @ as well as the flags. + .macro no_v7_barrier, tmp, tgt + mrc p15, 0, \tmp, c0, c2, 4 @ ID_ISAR4 + tst \tmp, #0xf << 16 + beq \tgt + .endm + + @ The following macros will use zreg as a temp + @ register, and will zero it after use. + .macro __dsb, zreg + no_v7_barrier \zreg, .L__dsb\@ ARM( .inst 0xf57ff04f @ v7+ dsb ) THUMB( dsb ) + mov \zreg, #0 +.L__dsb\@: mcreq p15, 0, \zreg, c7, c10, 4 @ dsb .endm - .macro v7dmb + .macro __dmb, zreg + no_v7_barrier \zreg, .L__dmb\@ ARM( .inst 0xf57ff05f @ v7+ dmb ) THUMB( dmb ) + mov \zreg, #0 +.L__dmb\@: mcreq p15, 0, \zreg, c7, c10, 5 @ dmb .endm - .macro v7isb + .macro __isb, zreg + no_v7_barrier \zreg, .L__isb\@ ARM( .inst 0xf57ff06f @ v7+ isb ) THUMB( isb ) + mov \zreg, #0 +.L__isb\@: mcreq p15, 0, \zreg, c7, c5, 4 @ isb .endm /* @@ -841,8 +862,7 @@ __armv7_mmu_cache_on: tst r11, #0xf @ VMSA movne r6, #CB_BITS | 0x02 @ !XN blne __setup_mmu - mov r0, #0 - v7dsb @ drain write buffer + __dsb r0 @ drain write buffer tst r11, #0xf @ VMSA mcrne p15, 0, r0, c8, c7, 0 @ flush I,D TLBs #endif @@ -864,11 +884,10 @@ __armv7_mmu_cache_on: mcrne p15, 0, r1, c3, c0, 0 @ load domain access control mcrne p15, 0, r6, c2, c0, 2 @ load ttb control #endif - v7isb + __isb lr mcr p15, 0, r0, c1, c0, 0 @ load control register mrc p15, 0, r0, c1, c0, 0 @ and read it back - mov r0, #0 - v7isb + __isb r0 mov pc, r12 __fa526_cache_on: @@ -1169,8 +1188,8 @@ __armv7_mmu_cache_off: mcr p15, 0, r0, c8, c7, 0 @ invalidate whole TLB #endif mcr p15, 0, r0, c7, c5, 6 @ invalidate BTC - v7dsb - v7isb + __dsb r0 + __isb r0 mov pc, r12 /* @@ -1233,7 +1252,7 @@ __armv7_mmu_cache_flush: mcr p15, 0, r10, c7, c14, 0 @ clean+invalidate D b iflush hierarchical: - v7dmb + __dmb r10 stmfd sp!, {r0-r7, r9-r11} mrc p15, 1, r0, c0, c0, 1 @ read clidr ands r3, r0, #0x7000000 @ extract loc from clidr @@ -1247,7 +1266,7 @@ loop1: cmp r1, #2 @ see what cache we have at this level blt skip @ skip if no cache, or just i-cache mcr p15, 2, r10, c0, c0, 0 @ select current cache level in cssr - v7isb @ isb to sych the new cssr&csidr + __isb r1 @ isb to sych the new cssr&csidr mrc p15, 1, r1, c0, c0, 0 @ read the new csidr and r2, r1, #7 @ extract the length of the cache lines add r2, r2, #4 @ add 4 (line length offset) @@ -1279,10 +1298,10 @@ finished: mov r10, #0 @ switch back to cache level 0 mcr p15, 2, r10, c0, c0, 0 @ select current cache level in cssr iflush: - v7dsb + __dsb r10 mcr p15, 0, r10, c7, c5, 0 @ invalidate I+BTB - v7dsb - v7isb + __dsb r10 + __isb r10 mov pc, lr __armv5tej_mmu_cache_flush: -- Jazz is not dead. It just smells funny...
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