From mboxrd@z Thu Jan 1 00:00:00 1970 From: murzin.v@gmail.com (Vladimir Murzin) Date: Sun, 27 Apr 2014 10:21:17 +0100 Subject: [RFC PATCH] arm64: make bitops 32-bit tolerant Message-ID: <1398590477-15375-1-git-send-email-murzin.v@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Xen assumes that bit operations are able to operate on 32-bit size and alignment [1]. For arm64 bitops are based on atomic exclusive load/store instructions to guarantee that changes are made atomically. However, these instructions require that address to be aligned to the data size. Because, by default, bitops operates on 64-bit size it implies that address should be aligned appropriately. All these lead to breakage of Xen assumption for bitops properties. This patch turns bitops to operate on 32-bit size/alignment. [1] http://www.gossamer-threads.com/lists/xen/devel/325613 Cc: catalin.marinas at arm.com Cc: will.deacon at arm.com Cc: david.vrabel at citrix.com Cc: Ian.Campbell at citrix.com Signed-off-by: Vladimir Murzin --- With this patch applied I was able to boot both Dom0 and DomU. @Pranav: Could I have your Tested-by on this patch? arch/arm64/lib/bitops.S | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-) diff --git a/arch/arm64/lib/bitops.S b/arch/arm64/lib/bitops.S index 7dac371..a6acfff 100644 --- a/arch/arm64/lib/bitops.S +++ b/arch/arm64/lib/bitops.S @@ -26,14 +26,14 @@ */ .macro bitop, name, instr ENTRY( \name ) - and w3, w0, #63 // Get bit offset + and w3, w0, #31 // Get bit offset eor w0, w0, w3 // Clear low bits mov x2, #1 add x1, x1, x0, lsr #3 // Get word offset lsl x3, x2, x3 // Create mask -1: ldxr x2, [x1] - \instr x2, x2, x3 - stxr w0, x2, [x1] +1: ldxr w2, [x1] + \instr w2, w2, w3 + stxr w0, w2, [x1] cbnz w0, 1b ret ENDPROC(\name ) @@ -41,15 +41,15 @@ ENDPROC(\name ) .macro testop, name, instr ENTRY( \name ) - and w3, w0, #63 // Get bit offset + and w3, w0, #31 // Get bit offset eor w0, w0, w3 // Clear low bits mov x2, #1 add x1, x1, x0, lsr #3 // Get word offset lsl x4, x2, x3 // Create mask -1: ldxr x2, [x1] +1: ldxr w2, [x1] lsr x0, x2, x3 // Save old value of bit - \instr x2, x2, x4 // toggle bit - stlxr w5, x2, [x1] + \instr w2, w2, w4 // toggle bit + stlxr w5, w2, [x1] cbnz w5, 1b dmb ish and x0, x0, #1 -- 1.8.3.2