Hi Vladimir,
On 08/09/16 17:06, Vladimir Murzin wrote:
> Currently GIC backend is selected via alternative framework and this
> is fine. We are going to introduce vgic-v3 to 32-bit world and there
> we don't have patching framework in hand, so we can either check
> support for GICv3 every time we need to choose which backend to use or
> try to optimise it by using static keys. The later looks quite
> promising because we can share logic involved in selecting GIC backend
> between architectures if both uses static keys.
>
> This patch moves arm64 from alternative to static keys framework for
> selecting GIC backend. To make static keys work on hyp side we need to
> make sure that hyp can access to the key which is RW data. For that
> purpose introduce __hyp_data section we can map to hyp and place the
> key there.
>
> Signed-off-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_host.h | 13 +++++++++++++
> arch/arm/include/asm/kvm_hyp.h | 2 --
> arch/arm/include/asm/virt.h | 8 ++++++++
> arch/arm/kernel/vmlinux.lds.S | 6 ++++++
> arch/arm/kvm/arm.c | 19 +++++++++++++++++++
> arch/arm64/include/asm/kvm_host.h | 15 +++++++++++++++
> arch/arm64/include/asm/kvm_hyp.h | 2 --
> arch/arm64/include/asm/virt.h | 7 +++++++
> arch/arm64/kernel/vmlinux.lds.S | 6 ++++++
> arch/arm64/kvm/hyp/switch.c | 19 +++++++++----------
> 10 files changed, 83 insertions(+), 14 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index de338d9..bfa6eec 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -21,11 +21,14 @@
>
> #include <linux/types.h>
> #include <linux/kvm_types.h>
> +#include <linux/jump_label.h>
> +
> #include <asm/kvm.h>
> #include <asm/kvm_asm.h>
> #include <asm/kvm_mmio.h>
> #include <asm/fpstate.h>
> #include <kvm/arm_arch_timer.h>
> +#include <asm/cputype.h>
>
> #define __KVM_HAVE_ARCH_INTC_INITIALIZED
>
> @@ -310,4 +313,14 @@ static inline int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
> return -ENXIO;
> }
>
> +extern struct static_key_false kvm_gicv3_cpuif;
I think we should follow the model set by kvm_vgic_global_state, which
is declared in arm_vgic.h. Even better, we should *embed* the static key
in this structure. This will reduce the clutter and we wouldn't have to
deal with all the section stuff (the hyp_data thing is a good cleanup,
but I'd like to see it as a separate patch if possible).
> +
> +static inline bool kvm_arm_support_gicv3_cpuif(void)
> +{
> + if (IS_ENABLED(CONFIG_ARM_GIC_V3))
> + return !!cpuid_feature_extract(CPUID_EXT_PFR1, 28);
> + else
> + return false;
> +}
> +
> #endif /* __ARM_KVM_HOST_H__ */
> diff --git a/arch/arm/include/asm/kvm_hyp.h b/arch/arm/include/asm/kvm_hyp.h
> index 6eaff28..bd9434e 100644
> --- a/arch/arm/include/asm/kvm_hyp.h
> +++ b/arch/arm/include/asm/kvm_hyp.h
> @@ -23,8 +23,6 @@
> #include <asm/kvm_mmu.h>
> #include <asm/vfp.h>
>
> -#define __hyp_text __section(.hyp.text) notrace
> -
> #define __ACCESS_CP15(CRn, Op1, CRm, Op2) \
> "mrc", "mcr", __stringify(p15, Op1, %0, CRn, CRm, Op2), u32
> #define __ACCESS_CP15_64(Op1, CRm) \
> diff --git a/arch/arm/include/asm/virt.h b/arch/arm/include/asm/virt.h
> index a2e75b8..e61a809 100644
> --- a/arch/arm/include/asm/virt.h
> +++ b/arch/arm/include/asm/virt.h
> @@ -28,6 +28,9 @@
> */
> #define BOOT_CPU_MODE_MISMATCH PSR_N_BIT
>
> +#define __hyp_text __section(.hyp.text) notrace
> +#define __hyp_data __section(.hyp.data)
> +
> #ifndef __ASSEMBLY__
> #include <asm/cacheflush.h>
>
> @@ -87,6 +90,11 @@ extern char __hyp_idmap_text_end[];
> /* The section containing the hypervisor text */
> extern char __hyp_text_start[];
> extern char __hyp_text_end[];
> +
> +/* The section containing the hypervisor data */
> +extern char __hyp_data_start[];
> +extern char __hyp_data_end[];
> +
> #endif
>
> #endif /* __ASSEMBLY__ */
> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S
> index d24e5dd..6d53824 100644
> --- a/arch/arm/kernel/vmlinux.lds.S
> +++ b/arch/arm/kernel/vmlinux.lds.S
> @@ -25,6 +25,11 @@
> *(.hyp.text) \
> VMLINUX_SYMBOL(__hyp_text_end) = .;
>
> +#define HYPERVISOR_DATA \
> + VMLINUX_SYMBOL(__hyp_data_start) = .; \
> + *(.hyp.data) \
> + VMLINUX_SYMBOL(__hyp_data_end) = .;
> +
> #define IDMAP_TEXT \
> ALIGN_FUNCTION(); \
> VMLINUX_SYMBOL(__idmap_text_start) = .; \
> @@ -256,6 +261,7 @@ SECTIONS
> */
> DATA_DATA
> CONSTRUCTORS
> + HYPERVISOR_DATA
If you follow my idea of of embedding the static key, we can defer all
of this to another patch set.
>
> _edata = .;
> }
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 75f130e..f966763 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -27,6 +27,7 @@
> #include <linux/mman.h>
> #include <linux/sched.h>
> #include <linux/kvm.h>
> +#include <linux/irqchip/arm-gic-v3.h>
> #include <trace/events/kvm.h>
> #include <kvm/arm_pmu.h>
>
> @@ -68,6 +69,9 @@ static bool vgic_present;
>
> static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
>
> +/* GIC system register CPU interface */
> +__hyp_data DEFINE_STATIC_KEY_FALSE(kvm_gicv3_cpuif);
> +
> static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
> {
> BUG_ON(preemptible());
> @@ -1178,6 +1182,14 @@ static int init_common_resources(void)
> return -ENOMEM;
> }
>
> + if (kvm_arm_support_gicv3_cpuif()) {
Why do we need to check this? If we identify a GICv3 (as exposed by the
host GIC driver), let's just use that.
> + if (!gic_enable_sre())
> + kvm_info("GIC CPU interface present but disabled by higher exception level\n");
Do you really want to try and enable SRE there? It feels wrong, as it
will already have been enabled by the host driver. Also, we don't
support having GICv3 in a non-SRE configuration (firmware must expose a
GICv2 in that case).
> +
> + static_branch_enable(&kvm_gicv3_cpuif);
> + kvm_info("GIC system register CPU interface\n");
> + }
Can this whole hunk be moved to the vgic initialization instead?
> +
> return 0;
> }
>
> @@ -1297,6 +1309,13 @@ static int init_hyp_mode(void)
> goto out_err;
> }
>
> + err = create_hyp_mappings(kvm_ksym_ref(__hyp_data_start),
> + kvm_ksym_ref(__hyp_data_end), PAGE_HYP);
> + if (err) {
> + kvm_err("Cannot map hyp data section\n");
> + goto out_err;
> + }
> +
> err = create_hyp_mappings(kvm_ksym_ref(__start_rodata),
> kvm_ksym_ref(__end_rodata), PAGE_HYP_RO);
> if (err) {
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3eda975..1da74e8 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -24,6 +24,9 @@
>
> #include <linux/types.h>
> #include <linux/kvm_types.h>
> +#include <linux/jump_label.h>
> +
> +#include <asm/cpufeature.h>
> #include <asm/kvm.h>
> #include <asm/kvm_asm.h>
> #include <asm/kvm_mmio.h>
> @@ -390,4 +393,16 @@ static inline void __cpu_init_stage2(void)
> "PARange is %d bits, unsupported configuration!", parange);
> }
>
> +extern struct static_key_false kvm_gicv3_cpuif;
> +
> +static inline bool kvm_arm_support_gicv3_cpuif(void)
> +{
> + int reg = read_system_reg(SYS_ID_AA64PFR0_EL1);
> +
> + if (IS_ENABLED(CONFIG_ARM_GIC_V3))
> + return !!cpuid_feature_extract_unsigned_field(reg, ID_AA64PFR0_GIC_SHIFT);
> +
> + return false;
> +}
> +
> #endif /* __ARM64_KVM_HOST_H__ */
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index cff5105..5c4ac82 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -23,8 +23,6 @@
> #include <asm/kvm_mmu.h>
> #include <asm/sysreg.h>
>
> -#define __hyp_text __section(.hyp.text) notrace
> -
> #define read_sysreg_elx(r,nvh,vh) \
> ({ \
> u64 reg; \
> diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
> index 1788545..c49426e 100644
> --- a/arch/arm64/include/asm/virt.h
> +++ b/arch/arm64/include/asm/virt.h
> @@ -42,6 +42,9 @@
> #define BOOT_CPU_MODE_EL1 (0xe11)
> #define BOOT_CPU_MODE_EL2 (0xe12)
>
> +#define __hyp_text __section(.hyp.text) notrace
> +#define __hyp_data __section(.hyp.data)
> +
> #ifndef __ASSEMBLY__
>
> #include <asm/ptrace.h>
> @@ -95,6 +98,10 @@ extern char __hyp_idmap_text_end[];
> extern char __hyp_text_start[];
> extern char __hyp_text_end[];
>
> +/* The section containing the hypervisor data */
> +extern char __hyp_data_start[];
> +extern char __hyp_data_end[];
> +
> #endif /* __ASSEMBLY__ */
>
> #endif /* ! __ASM__VIRT_H */
> diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S
> index 659963d..ea94a10 100644
> --- a/arch/arm64/kernel/vmlinux.lds.S
> +++ b/arch/arm64/kernel/vmlinux.lds.S
> @@ -40,6 +40,11 @@ jiffies = jiffies_64;
> *(.hyp.text) \
> VMLINUX_SYMBOL(__hyp_text_end) = .;
>
> +#define HYPERVISOR_DATA \
> + VMLINUX_SYMBOL(__hyp_data_start) = .; \
> + .hyp.data : {*(.hyp.data)} \
> + VMLINUX_SYMBOL(__hyp_data_end) = .;
> +
> #define IDMAP_TEXT \
> . = ALIGN(SZ_4K); \
> VMLINUX_SYMBOL(__idmap_text_start) = .; \
> @@ -185,6 +190,7 @@ SECTIONS
> _data = .;
> _sdata = .;
> RW_DATA_SECTION(L1_CACHE_BYTES, PAGE_SIZE, THREAD_SIZE)
> + HYPERVISOR_DATA
> PECOFF_EDATA_PADDING
> _edata = .;
>
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 5a84b45..cdc1360 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -126,17 +126,13 @@ static void __hyp_text __deactivate_vm(struct kvm_vcpu *vcpu)
> write_sysreg(0, vttbr_el2);
> }
>
> -static hyp_alternate_select(__vgic_call_save_state,
> - __vgic_v2_save_state, __vgic_v3_save_state,
> - ARM64_HAS_SYSREG_GIC_CPUIF);
> -
> -static hyp_alternate_select(__vgic_call_restore_state,
> - __vgic_v2_restore_state, __vgic_v3_restore_state,
> - ARM64_HAS_SYSREG_GIC_CPUIF);
> -
> static void __hyp_text __vgic_save_state(struct kvm_vcpu *vcpu)
> {
> - __vgic_call_save_state()(vcpu);
> + if (static_branch_unlikely(&kvm_gicv3_cpuif))
> + __vgic_v3_save_state(vcpu);
> + else
> + __vgic_v2_save_state(vcpu);
> +
> write_sysreg(read_sysreg(hcr_el2) & ~HCR_INT_OVERRIDE, hcr_el2);
> }
>
> @@ -149,7 +145,10 @@ static void __hyp_text __vgic_restore_state(struct kvm_vcpu *vcpu)
> val |= vcpu->arch.irq_lines;
> write_sysreg(val, hcr_el2);
>
> - __vgic_call_restore_state()(vcpu);
> + if (static_branch_unlikely(&kvm_gicv3_cpuif))
> + __vgic_v3_restore_state(vcpu);
> + else
> + __vgic_v2_restore_state(vcpu);
> }
>
> static bool __hyp_text __true_value(void)
>
Thanks,
M.
--
Jazz is not dead. It just smells funny...
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
