Re: [PATCH v4 08/20] kvm: arm64: Configure VTCR_EL2 per VM

Christoffer Dall
2018-08-30T10:02:29Z

On Wed, Jul 18, 2018 at 10:18:51AM +0100, Suzuki K Poulose wrote:
> Add support for setting the VTCR_EL2 per VM, rather than hard
> coding a value at boot time per CPU. This would allow us to tune
> the stage2 page table parameters per VM in the later changes.
>
> We compute the VTCR fields based on the system wide sanitised
> feature registers, except for the hardware management of Access
> Flags (VTCR_EL2.HA). It is fine to run a system with a mix of
> CPUs that may or may not update the page table Access Flags.
> Since the bit is RES0 on CPUs that don't support it, the bit
> should be ignored on them.

Acked-by: Christoffer Dall <christoffer.dall@arm.com>

>
> Suggested-by: Marc Zyngier <marc.zyngier@arm.com>
> Cc: Christoffer Dall <cdall@kernel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> ---
> arch/arm/include/asm/kvm_host.h | 5 +++
> arch/arm64/include/asm/kvm_arm.h | 3 +-
> arch/arm64/include/asm/kvm_asm.h | 2 --
> arch/arm64/include/asm/kvm_host.h | 15 +++++---
> arch/arm64/include/asm/kvm_hyp.h | 1 +
> arch/arm64/kvm/guest.c | 38 ++++++++++++++++++++-
> arch/arm64/kvm/hyp/Makefile | 1 -
> arch/arm64/kvm/hyp/s2-setup.c | 72 ---------------------------------------
> virt/kvm/arm/arm.c | 4 +++
> 9 files changed, 58 insertions(+), 83 deletions(-)
> delete mode 100644 arch/arm64/kvm/hyp/s2-setup.c
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 1f1fe410..86f43ab 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -350,4 +350,9 @@ static inline void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu) {}
> struct kvm *kvm_arch_alloc_vm(void);
> void kvm_arch_free_vm(struct kvm *kvm);
>
> +static inline int kvm_arm_config_vm(struct kvm *kvm)
> +{
> + return 0;
> +}
> +
> #endif /* __ARM_KVM_HOST_H__ */
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 3dffd38..87d2db6 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -134,8 +134,7 @@
> * 40 bits wide (T0SZ = 24). Systems with a PARange smaller than 40 bits are
> * not known to exist and will break with this configuration.
> *
> - * VTCR_EL2.PS is extracted from ID_AA64MMFR0_EL1.PARange at boot time
> - * (see hyp-init.S).
> + * The VTCR_EL2 is configured per VM and is initialised in kvm_arm_config_vm().
> *
> * Note that when using 4K pages, we concatenate two first level page tables
> * together. With 16K pages, we concatenate 16 first level page tables.
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 102b5a5..0b53c72 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -72,8 +72,6 @@ extern void __vgic_v3_init_lrs(void);
>
> extern u32 __kvm_get_mdcr_el2(void);
>
> -extern u32 __init_stage2_translation(void);
> -
> /* Home-grown __this_cpu_{ptr,read} variants that always work at HYP */
> #define __hyp_this_cpu_ptr(sym) \
> ({ \
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index fe8777b..b1ffaf3 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -61,12 +61,13 @@ struct kvm_arch {
> u64 vmid_gen;
> u32 vmid;
>
> - /* 1-level 2nd stage table and lock */
> - spinlock_t pgd_lock;
> + /* stage2 entry level table */
> pgd_t *pgd;
>
> /* VTTBR value associated with above pgd and vmid */
> u64 vttbr;
> + /* VTCR_EL2 value for this VM */
> + u64 vtcr;
>
> /* The last vcpu id that ran on each physical CPU */
> int __percpu *last_vcpu_ran;
> @@ -442,10 +443,12 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
>
> static inline void __cpu_init_stage2(void)
> {
> - u32 parange = kvm_call_hyp(__init_stage2_translation);
> + u32 ps;
>
> - WARN_ONCE(parange < 40,
> - "PARange is %d bits, unsupported configuration!", parange);
> + /* Sanity check for minimum IPA size support */
> + ps = id_aa64mmfr0_parange_to_phys_shift(read_sysreg(id_aa64mmfr0_el1) & 0x7);
> + WARN_ONCE(ps < 40,
> + "PARange is %d bits, unsupported configuration!", ps);
> }
>
> /* Guest/host FPSIMD coordination helpers */
> @@ -513,4 +516,6 @@ void kvm_vcpu_put_sysregs(struct kvm_vcpu *vcpu);
> struct kvm *kvm_arch_alloc_vm(void);
> void kvm_arch_free_vm(struct kvm *kvm);
>
> +int kvm_arm_config_vm(struct kvm *kvm);
> +
> #endif /* __ARM64_KVM_HOST_H__ */
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 82f9994..6f47cc7 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -158,6 +158,7 @@ void __noreturn __hyp_do_panic(unsigned long, ...);
> /* Must be called from hyp code running at EL2 */
> static __always_inline void __hyp_text __load_guest_stage2(struct kvm *kvm)
> {
> + write_sysreg(kvm->arch.vtcr, vtcr_el2);
> write_sysreg(kvm->arch.vttbr, vttbr_el2);
> }
>
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 56a0260..d24ee23 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -26,11 +26,13 @@
> #include <linux/vmalloc.h>
> #include <linux/fs.h>
> #include <kvm/arm_psci.h>
> -#include <asm/cputype.h>
> #include <linux/uaccess.h>
> +#include <asm/cpufeature.h>
> +#include <asm/cputype.h>
> #include <asm/kvm.h>
> #include <asm/kvm_emulate.h>
> #include <asm/kvm_coproc.h>
> +#include <asm/kvm_mmu.h>
>
> #include "trace.h"
>
> @@ -458,3 +460,37 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
>
> return ret;
> }
> +
> +/*
> + * Configure the VTCR_EL2 for this VM. The VTCR value is common
> + * across all the physical CPUs on the system. We use system wide
> + * sanitised values to fill in different fields, except for Hardware
> + * Management of Access Flags. HA Flag is set unconditionally on
> + * all CPUs, as it is safe to run with or without the feature and
> + * the bit is RES0 on CPUs that don't support it.
> + */
> +int kvm_arm_config_vm(struct kvm *kvm)
> +{
> + u64 vtcr = VTCR_EL2_FLAGS;
> + u64 parange;
> +
> +
> + parange = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1) & 7;
> + if (parange > ID_AA64MMFR0_PARANGE_MAX)
> + parange = ID_AA64MMFR0_PARANGE_MAX;
> + vtcr |= parange << VTCR_EL2_PS_SHIFT;
> +
> + /*
> + * Enable the Hardware Access Flag management, unconditionally
> + * on all CPUs. The features is RES0 on CPUs without the support
> + * and must be ignored by the CPUs.
> + */
> + vtcr |= VTCR_EL2_HA;
> +
> + /* Set the vmid bits */
> + vtcr |= (kvm_get_vmid_bits() == 16) ?
> + VTCR_EL2_VS_16BIT :
> + VTCR_EL2_VS_8BIT;
> + kvm->arch.vtcr = vtcr;
> + return 0;
> +}
> diff --git a/arch/arm64/kvm/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> index 4313f74..1b80a9a 100644
> --- a/arch/arm64/kvm/hyp/Makefile
> +++ b/arch/arm64/kvm/hyp/Makefile
> @@ -18,7 +18,6 @@ obj-$(CONFIG_KVM_ARM_HOST) += switch.o
> obj-$(CONFIG_KVM_ARM_HOST) += fpsimd.o
> obj-$(CONFIG_KVM_ARM_HOST) += tlb.o
> obj-$(CONFIG_KVM_ARM_HOST) += hyp-entry.o
> -obj-$(CONFIG_KVM_ARM_HOST) += s2-setup.o
>
> # KVM code is run at a different exception code with a different map, so
> # compiler instrumentation that inserts callbacks or checks into the code may
> diff --git a/arch/arm64/kvm/hyp/s2-setup.c b/arch/arm64/kvm/hyp/s2-setup.c
> deleted file mode 100644
> index e1ca672..0000000
> --- a/arch/arm64/kvm/hyp/s2-setup.c
> +++ /dev/null
> @@ -1,72 +0,0 @@
> -/*
> - * Copyright (C) 2016 - ARM Ltd
> - * Author: Marc Zyngier <marc.zyngier@arm.com>
> - *
> - * 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/types.h>
> -#include <asm/kvm_arm.h>
> -#include <asm/kvm_asm.h>
> -#include <asm/kvm_hyp.h>
> -#include <asm/cpufeature.h>
> -
> -u32 __hyp_text __init_stage2_translation(void)
> -{
> - u64 val = VTCR_EL2_FLAGS;
> - u64 parange;
> - u32 phys_shift;
> - u64 tmp;
> -
> - /*
> - * Read the PARange bits from ID_AA64MMFR0_EL1 and set the PS
> - * bits in VTCR_EL2. Amusingly, the PARange is 4 bits, but the
> - * allocated values are limited to 3bits.
> - */
> - parange = read_sysreg(id_aa64mmfr0_el1) & 7;
> - if (parange > ID_AA64MMFR0_PARANGE_MAX)
> - parange = ID_AA64MMFR0_PARANGE_MAX;
> - val |= parange << VTCR_EL2_PS_SHIFT;
> -
> - /* Compute the actual PARange... */
> - phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
> -
> - /*
> - * ... and clamp it to 40 bits, unless we have some braindead
> - * HW that implements less than that. In all cases, we'll
> - * return that value for the rest of the kernel to decide what
> - * to do.
> - */
> - val |= VTCR_EL2_T0SZ(phys_shift > 40 ? 40 : phys_shift);
> -
> - /*
> - * Check the availability of Hardware Access Flag / Dirty Bit
> - * Management in ID_AA64MMFR1_EL1 and enable the feature in VTCR_EL2.
> - */
> - tmp = (read_sysreg(id_aa64mmfr1_el1) >> ID_AA64MMFR1_HADBS_SHIFT) & 0xf;
> - if (tmp)
> - val |= VTCR_EL2_HA;
> -
> - /*
> - * Read the VMIDBits bits from ID_AA64MMFR1_EL1 and set the VS
> - * bit in VTCR_EL2.
> - */
> - tmp = (read_sysreg(id_aa64mmfr1_el1) >> ID_AA64MMFR1_VMIDBITS_SHIFT) & 0xf;
> - val |= (tmp == ID_AA64MMFR1_VMIDBITS_16) ?
> - VTCR_EL2_VS_16BIT :
> - VTCR_EL2_VS_8BIT;
> -
> - write_sysreg(val, vtcr_el2);
> -
> - return phys_shift;
> -}
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 04e554c..37e46e4 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -122,6 +122,10 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> if (type)
> return -EINVAL;
>
> + ret = kvm_arm_config_vm(kvm);
> + if (ret)
> + return ret;
> +
> kvm->arch.last_vcpu_ran = alloc_percpu(typeof(*kvm->arch.last_vcpu_ran));
> if (!kvm->arch.last_vcpu_ran)
> return -ENOMEM;
> --
> 2.7.4
>
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