From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bilbo.ozlabs.org (bilbo.ozlabs.org [203.10.76.25]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "bilbo.ozlabs.org", Issuer "CAcert Class 3 Root" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 0C66EDDE23 for ; Thu, 2 Apr 2009 15:02:43 +1100 (EST) From: Michael Neuling To: benh@kernel.crashing.org, paulus@samba.org MIME-Version: 1.0 Subject: [PATCH] powerpc: change giveup_fpu/altivec to disable VSX for current Date: Thu, 02 Apr 2009 15:02:42 +1100 Message-ID: <2074.1238644962@neuling.org> Cc: linuxppc-dev@ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , When we call giveup_fpu, we need to need to turn off VSX in current. If we don't, on return to current it may execute a VSX instruction (before the next FP), and not have it's register state refreshed correctly from the thread_struct. Ditto for altivec. This caused a bug where an unaligned lfs or stfs (which calls giveup_fpu so it can use the FPRs) to return to userspace with FP off but VSX on. Then if a VSX instruction is executed, before another FP instruction, it will proceed without another exception and hence have the incorrect register state for VSX registers 0-31. lfs unaligned <- alignment exception turns FP off but leaves VSX on VSX instruction <- no exception since VSX on, hence we get the wrong VSX register values for VSX registers 0-31 (overlapping the FPRs) Signed-off-by: Michael Neuling --- arch/powerpc/kernel/fpu.S | 5 +++++ arch/powerpc/kernel/misc_64.S | 8 ++++++++ 2 files changed, 13 insertions(+) Index: linux-2.6-ozlabs/arch/powerpc/kernel/fpu.S =================================================================== --- linux-2.6-ozlabs.orig/arch/powerpc/kernel/fpu.S +++ linux-2.6-ozlabs/arch/powerpc/kernel/fpu.S @@ -145,6 +145,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_VSX) beq 1f PPC_LL r4,_MSR-STACK_FRAME_OVERHEAD(r5) li r3,MSR_FP|MSR_FE0|MSR_FE1 +#ifdef CONFIG_VSX +BEGIN_FTR_SECTION + oris r3,r3,MSR_VSX@h +END_FTR_SECTION_IFSET(CPU_FTR_VSX) +#endif andc r4,r4,r3 /* disable FP for previous task */ PPC_STL r4,_MSR-STACK_FRAME_OVERHEAD(r5) 1: Index: linux-2.6-ozlabs/arch/powerpc/kernel/misc_64.S =================================================================== --- linux-2.6-ozlabs.orig/arch/powerpc/kernel/misc_64.S +++ linux-2.6-ozlabs/arch/powerpc/kernel/misc_64.S @@ -495,7 +495,15 @@ _GLOBAL(giveup_altivec) stvx vr0,r4,r3 beq 1f ld r4,_MSR-STACK_FRAME_OVERHEAD(r5) +#ifdef CONFIG_VSX +BEGIN_FTR_SECTION + lis r3,(MSR_VEC|MSR_VSX)@h +FTR_SECTION_ELSE + lis r3,MSR_VEC@h +ALT_FTR_SECTION_END_IFSET(CPU_FTR_VSX) +#else lis r3,MSR_VEC@h +#endif andc r4,r4,r3 /* disable FP for previous task */ std r4,_MSR-STACK_FRAME_OVERHEAD(r5) 1: