On Tue, Dec 01, 2015 at 11:57:16AM +0000, Marc Zyngier wrote: > On 01/12/15 11:50, Christoffer Dall wrote: > > On Tue, Dec 01, 2015 at 12:44:26PM +0100, Christoffer Dall wrote: > >> On Tue, Dec 01, 2015 at 11:32:20AM +0000, Marc Zyngier wrote: > >>> On 30/11/15 19:50, Christoffer Dall wrote: > >>>> On Fri, Nov 27, 2015 at 06:49:58PM +0000, Marc Zyngier wrote: > >>>>> Implement the vgic-v3 save restore as a direct translation of > >>>>> the assembly code version. > >>>>> > >>>>> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> > >>>>> --- > >>>>> arch/arm64/kvm/hyp/Makefile | 1 + > >>>>> arch/arm64/kvm/hyp/hyp.h | 3 + > >>>>> arch/arm64/kvm/hyp/vgic-v3-sr.c | 222 ++++++++++++++++++++++++++++++++++++++++ > >>>>> 3 files changed, 226 insertions(+) > >>>>> create mode 100644 arch/arm64/kvm/hyp/vgic-v3-sr.c > >>>>> > >>>>> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile > >>>>> index d8d5968..d1e38ce 100644 > >>>>> --- a/arch/arm64/kvm/hyp/Makefile > >>>>> +++ b/arch/arm64/kvm/hyp/Makefile > >>>>> @@ -3,3 +3,4 @@ > >>>>> # > >>>>> > >>>>> obj-$(CONFIG_KVM_ARM_HOST) += vgic-v2-sr.o > >>>>> +obj-$(CONFIG_KVM_ARM_HOST) += vgic-v3-sr.o > >>>>> diff --git a/arch/arm64/kvm/hyp/hyp.h b/arch/arm64/kvm/hyp/hyp.h > >>>>> index 78f25c4..a31cb6e 100644 > >>>>> --- a/arch/arm64/kvm/hyp/hyp.h > >>>>> +++ b/arch/arm64/kvm/hyp/hyp.h > >>>>> @@ -30,5 +30,8 @@ > >>>>> void __vgic_v2_save_state(struct kvm_vcpu *vcpu); > >>>>> void __vgic_v2_restore_state(struct kvm_vcpu *vcpu); > >>>>> > >>>>> +void __vgic_v3_save_state(struct kvm_vcpu *vcpu); > >>>>> +void __vgic_v3_restore_state(struct kvm_vcpu *vcpu); > >>>>> + > >>>>> #endif /* __ARM64_KVM_HYP_H__ */ > >>>>> > >>>>> diff --git a/arch/arm64/kvm/hyp/vgic-v3-sr.c b/arch/arm64/kvm/hyp/vgic-v3-sr.c > >>>>> new file mode 100644 > >>>>> index 0000000..b490db5 > >>>>> --- /dev/null > >>>>> +++ b/arch/arm64/kvm/hyp/vgic-v3-sr.c > >>>>> @@ -0,0 +1,222 @@ > >>>>> +/* > >>>>> + * Copyright (C) 2012-2015 - ARM Ltd > >>>>> + * Author: Marc Zyngier <marc.zyngier@xxxxxxx> > >>>>> + * > >>>>> + * This program is free software; you can redistribute it and/or modify > >>>>> + * it under the terms of the GNU General Public License version 2 as > >>>>> + * published by the Free Software Foundation. > >>>>> + * > >>>>> + * This program is distributed in the hope that it will be useful, > >>>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of > >>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > >>>>> + * GNU General Public License for more details. > >>>>> + * > >>>>> + * You should have received a copy of the GNU General Public License > >>>>> + * along with this program. If not, see <http://www.gnu.org/licenses/>. > >>>>> + */ > >>>>> + > >>>>> +#include <linux/compiler.h> > >>>>> +#include <linux/irqchip/arm-gic-v3.h> > >>>>> +#include <linux/kvm_host.h> > >>>>> + > >>>>> +#include <asm/kvm_mmu.h> > >>>>> + > >>>>> +#include "hyp.h" > >>>>> + > >>>>> +/* > >>>>> + * We store LRs in reverse order to let the CPU deal with streaming > >>>>> + * access. Use this macro to make it look saner... > >>>>> + */ > >>>>> +#define LR_OFFSET(n) (15 - n) > >>>>> + > >>>>> +#define read_gicreg(r) \ > >>>>> + ({ \ > >>>>> + u64 reg; \ > >>>>> + asm volatile("mrs_s %0, " __stringify(r) : "=r" (reg)); \ > >>>>> + reg; \ > >>>>> + }) > >>>>> + > >>>>> +#define write_gicreg(v,r) \ > >>>>> + do { \ > >>>>> + u64 __val = (v); \ > >>>>> + asm volatile("msr_s " __stringify(r) ", %0" : : "r" (__val));\ > >>>>> + } while (0) > >>>> > >>>> remind me what the msr_s and mrs_s do compared to msr and mrs? > >>> > >>> They do the same job, only for the system registers which are not in the > >>> original ARMv8 architecture spec, and most likely not implemented by > >>> old(er) compilers. > >>> > >>>> are these the reason why we need separate macros to access the gic > >>>> registers compared to 'normal' sysregs? > >>> > >>> Indeed. > >>> > >>>>> + > >>>>> +/* vcpu is already in the HYP VA space */ > >>>>> +void __hyp_text __vgic_v3_save_state(struct kvm_vcpu *vcpu) > >>>>> +{ > >>>>> + struct vgic_v3_cpu_if *cpu_if = &vcpu->arch.vgic_cpu.vgic_v3; > >>>>> + u64 val; > >>>>> + u32 nr_lr, nr_pri; > >>>>> + > >>>>> + /* > >>>>> + * Make sure stores to the GIC via the memory mapped interface > >>>>> + * are now visible to the system register interface. > >>>>> + */ > >>>>> + dsb(st); > >>>>> + > >>>>> + cpu_if->vgic_vmcr = read_gicreg(ICH_VMCR_EL2); > >>>>> + cpu_if->vgic_misr = read_gicreg(ICH_MISR_EL2); > >>>>> + cpu_if->vgic_eisr = read_gicreg(ICH_EISR_EL2); > >>>>> + cpu_if->vgic_elrsr = read_gicreg(ICH_ELSR_EL2); > >>>>> + > >>>>> + write_gicreg(0, ICH_HCR_EL2); > >>>>> + val = read_gicreg(ICH_VTR_EL2); > >>>>> + nr_lr = val & 0xf; > >>>> > >>>> this is not technically nr_lr, it's max_lr or max_lr_idx or something > >>>> like that. > >>> > >>> Let's go for max_lr_idx then. > >>> > >>>>> + nr_pri = ((u32)val >> 29) + 1; > >>>> > >>>> nit: nr_pri_bits > >>>> > >>>>> + > >>>>> + switch (nr_lr) { > >>>>> + case 15: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(15)] = read_gicreg(ICH_LR15_EL2); > >>>>> + case 14: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(14)] = read_gicreg(ICH_LR14_EL2); > >>>>> + case 13: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(13)] = read_gicreg(ICH_LR13_EL2); > >>>>> + case 12: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(12)] = read_gicreg(ICH_LR12_EL2); > >>>>> + case 11: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(11)] = read_gicreg(ICH_LR11_EL2); > >>>>> + case 10: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(10)] = read_gicreg(ICH_LR10_EL2); > >>>>> + case 9: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(9)] = read_gicreg(ICH_LR9_EL2); > >>>>> + case 8: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(8)] = read_gicreg(ICH_LR8_EL2); > >>>>> + case 7: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(7)] = read_gicreg(ICH_LR7_EL2); > >>>>> + case 6: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(6)] = read_gicreg(ICH_LR6_EL2); > >>>>> + case 5: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(5)] = read_gicreg(ICH_LR5_EL2); > >>>>> + case 4: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(4)] = read_gicreg(ICH_LR4_EL2); > >>>>> + case 3: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(3)] = read_gicreg(ICH_LR3_EL2); > >>>>> + case 2: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(2)] = read_gicreg(ICH_LR2_EL2); > >>>>> + case 1: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(1)] = read_gicreg(ICH_LR1_EL2); > >>>>> + case 0: > >>>>> + cpu_if->vgic_lr[LR_OFFSET(0)] = read_gicreg(ICH_LR0_EL2); > >>>> > >>>> I don't understand this; LR_OFFSET(0) == (15 - 0) == 15, so > >>>> > >>>> cpu_if->vgic_lr[15] = read_gicreg(ICH_LR0_EL2) ? > >>> > >>> Just like in the assembly version. We store the LRs in the order we read > >>> them so that we don't confuse the CPU by writing backward (believe it or > >>> not, CPUs do get horribly confused if you do that). > >> > >> but aren't we storing the wrong register to the wrong index in the > >> array? > >> > >> Do we really access cpu_if->vgic_lr[15..12] in the C-code if the system > >> only has 4 LRs? > >> > > ok, I looked at the code myself (not sure why I didn't do that in the > > first place) and indeed we use a different but with similar results > > macro to access the array from the C code. > > > > This is just insane to me, and we don't have a comment on the data > > structure saying "this is not stored the way you'd think it is". > > > > Why can't we just do: > > > > cpu_if->vgic_lr[3] = read_gicreg(ICH_LR3_EL2); > > cpu_if->vgic_lr[2] = read_gicreg(ICH_LR2_EL2); > > cpu_if->vgic_lr[1] = read_gicreg(ICH_LR1_EL2); > > cpu_if->vgic_lr[0] = read_gicreg(ICH_LR0_EL2); > > > > ? > > Because you're *really* killing performance by doing what are > essentially streaming read/writes in the opposite direction. CPU > prefetchers only work in one direction (incrementing the address). Doing > it backwards breaks it. > hmm, and what are prefetching with the stores here? Did anyone actually measure this or is it theoretically really slow? Anyway, for the purposes of rewriting the world-switch in C, this looks fine. I hope we can come up with something less convoluted some time, perhaps at least using the same macro for LR_INDEX and making the comments more clear. -Christoffer -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
