From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60985) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YUxh2-0003xb-P4 for qemu-devel@nongnu.org; Mon, 09 Mar 2015 09:26:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YUxgz-0003HQ-H4 for qemu-devel@nongnu.org; Mon, 09 Mar 2015 09:26:00 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:36215) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YUxgz-0003HK-5n for qemu-devel@nongnu.org; Mon, 09 Mar 2015 09:25:57 -0400 Received: by lbiz11 with SMTP id z11so44990365lbi.3 for ; Mon, 09 Mar 2015 06:25:56 -0700 (PDT) Date: Mon, 9 Mar 2015 14:26:11 +0100 From: Christoffer Dall Message-ID: <20150309132611.GB20559@cbox> References: <1425479753-18349-1-git-send-email-alex.bennee@linaro.org> <1425479753-18349-6-git-send-email-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1425479753-18349-6-git-send-email-alex.bennee@linaro.org> Subject: Re: [Qemu-devel] [PATCH v2 5/6] target-arm: kvm64 fix save/restore of SPSR regs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Alex =?iso-8859-1?Q?Benn=E9e?= Cc: Peter Maydell , kvm@vger.kernel.org, marc.zyngier@arm.com, qemu-devel@nongnu.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org On Wed, Mar 04, 2015 at 02:35:52PM +0000, Alex Bennée wrote: > From: Christoffer Dall > > The current code was negatively indexing the cpu state array and not > synchronizing banked spsr register state with the current mode's spsr > state, causing occasional failures with migration. > > Some munging is done to take care of the aarch64 mapping and also to > ensure the most current value of the spsr is updated to the banked > registers (relevant for KVM<->TCG migration). > > Signed-off-by: Christoffer Dall > Signed-off-by: Alex Bennée > > --- > v2 (ajb) > - minor tweaks and clarifications > v3 > - Use the correct bank index function for setting/getting env->spsr > - only deal with spsrs in elevated exception levels > > diff --git a/target-arm/kvm64.c b/target-arm/kvm64.c > index c60e989..45e5c3f 100644 > --- a/target-arm/kvm64.c > +++ b/target-arm/kvm64.c > @@ -140,6 +140,7 @@ int kvm_arch_put_registers(CPUState *cs, int level) > uint64_t val; > int i; > int ret; > + unsigned int el; > > ARMCPU *cpu = ARM_CPU(cs); > CPUARMState *env = &cpu->env; > @@ -206,9 +207,27 @@ int kvm_arch_put_registers(CPUState *cs, int level) > return ret; > } > > + /* Saved Program State Registers > + * > + * Before we restore from the banked_spsr[] array we need to > + * ensure that any modifications to env->spsr are correctly > + * reflected and map aarch64 exception levels if required. > + */ > + el = arm_current_el(env); > + if (el > 0) { > + if (is_a64(env)) { > + g_assert(el == 1); > + /* KVM only maps KVM_SPSR_SVC to KVM_SPSR_EL1 for aarch64 ATM */ not sure about the 'for aarch64' comment; I would say that it's for aarch32 support. Also, you can drop the ATM, since this is user space ABI that we don't change easily. don't you need to do env->banked_spsr[0] = env->spsr first? > + env->banked_spsr[1] = env->banked_spsr[0]; > + } else { > + i = bank_number(env->uncached_cpsr & CPSR_M); > + env->banked_spsr[i] = env->spsr; so here we don't need to worry about banked_spsr[1] = banked_spsr[0] because banked_spsr[0] is meaningless for 32-bit state and we only sync banked_spsr[1] and up to KVM, correct? I think this is what may deserve a comment. > + } > + } > + > for (i = 0; i < KVM_NR_SPSR; i++) { > reg.id = AARCH64_CORE_REG(spsr[i]); > - reg.addr = (uintptr_t) &env->banked_spsr[i - 1]; > + reg.addr = (uintptr_t) &env->banked_spsr[i+1]; > ret = kvm_vcpu_ioctl(cs, KVM_SET_ONE_REG, ®); > if (ret) { > return ret; > @@ -253,6 +272,7 @@ int kvm_arch_get_registers(CPUState *cs) > struct kvm_one_reg reg; > uint64_t val; > uint32_t fpr; > + unsigned int el; > int i; > int ret; > > @@ -325,15 +345,35 @@ int kvm_arch_get_registers(CPUState *cs) > return ret; > } > > + /* Fetch the SPSR registers > + * > + * KVM has an array of state indexed for all the possible aarch32 > + * privilage levels. Although not all are valid at all points privilege > + * there are some transitions possible which can access old state > + * so it is worth keeping them all. > + */ dubious comment overall > for (i = 0; i < KVM_NR_SPSR; i++) { > reg.id = AARCH64_CORE_REG(spsr[i]); > - reg.addr = (uintptr_t) &env->banked_spsr[i - 1]; > + reg.addr = (uintptr_t) &env->banked_spsr[i+1]; > ret = kvm_vcpu_ioctl(cs, KVM_GET_ONE_REG, ®); > if (ret) { > return ret; > } > } > > + el = arm_current_el(env); > + if (el > 0) { > + if (is_a64(env)) { > + g_assert(el == 1); > + /* KVM maps KVM_SPSR_SVC to KVM_SPSR_EL1 for aarch64 */ same as above > + env->banked_spsr[0] = env->banked_spsr[1]; > + i = aarch64_banked_spsr_index(el); > + } else { > + i = bank_number(env->uncached_cpsr & CPSR_M); same potential place for comment as above. > + } > + env->spsr = env->banked_spsr[i]; > + } > + > /* Advanced SIMD and FP registers */ > for (i = 0; i < 32; i++) { > reg.id = AARCH64_SIMD_CORE_REG(fp_regs.vregs[i]); > -- > 2.3.1 >