From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hr2.samba.org (hr2.samba.org [IPv6:2a01:4f8:192:486::147:1]) by lists.ozlabs.org (Postfix) with ESMTP id C85E61A0B87 for ; Mon, 7 Mar 2016 15:20:35 +1100 (AEDT) Date: Mon, 7 Mar 2016 15:19:52 +1100 From: Anton Blanchard To: Oliver O'Halloran Cc: linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] powerpc/process: fix altivec SPR not being saved Message-ID: <20160307151952.4df95a71@kryten> In-Reply-To: <1457303588-29173-1-git-send-email-oohall@gmail.com> References: <1457303588-29173-1-git-send-email-oohall@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Hi Oliver, > In save_sprs() in process.c contains the following test: > > if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) > t->vrsave = mfspr(SPRN_VRSAVE); > > CPU feature with the mask 0x1 is CPU_FTR_COHERENT_ICACHE so the test > is equivilent to: > > if (cpu_has_feature(CPU_FTR_ALTIVEC) && > cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) > > On CPUs without support for both (i.e G5) this results in vrsave not > being saved between context switches. The vector register > save/restore code doesn't use VRSAVE to determine which registers to > save/restore, but the value of VRSAVE is used to determine if altivec > is being used in several code paths. Nice catch, not sure how I missed that. As Ben suggests, it should definitely go to -stable as well. Feel free to add my sign off: Signed-off-by: Anton Blanchard Anton > Signed-off-by: Oliver O'Halloran > --- > arch/powerpc/kernel/process.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/powerpc/kernel/process.c > b/arch/powerpc/kernel/process.c index 8224852..5a4d4d1 100644 > --- a/arch/powerpc/kernel/process.c > +++ b/arch/powerpc/kernel/process.c > @@ -855,7 +855,7 @@ void restore_tm_state(struct pt_regs *regs) > static inline void save_sprs(struct thread_struct *t) > { > #ifdef CONFIG_ALTIVEC > - if (cpu_has_feature(cpu_has_feature(CPU_FTR_ALTIVEC))) > + if (cpu_has_feature(CPU_FTR_ALTIVEC)) > t->vrsave = mfspr(SPRN_VRSAVE); > #endif > #ifdef CONFIG_PPC_BOOK3S_64