Date:   Tue, 2 Oct 2018 09:48:22 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        marc.zyngier@....com, cdall@...nel.org, will.deacon@....com,
        dave.martin@....com, peter.maydell@...aro.org, pbonzini@...hat.com,
        rkrcmar@...hat.com, julien.grall@....com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 07/18] kvm: arm64: Configure VTCR_EL2 per VM

Hi Suzuki,

On 9/26/18 6:32 PM, 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.
> 
> Suggested-by: Marc Zyngier <marc.zyngier@....com>
> Acked-by: Christoffer Dall <cdall@...nel.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric
> ---
> Changes since v5:
>  - Set the missing TCR_T0SZ initialisation (Eric Auger)
>    and limit the T0SZ to the real CPU limit or KVM_PHYS_SHIFT
>    whichever is lower.
> ---
>  arch/arm64/include/asm/kvm_arm.h  |  3 +-
>  arch/arm64/include/asm/kvm_asm.h  |  2 -
>  arch/arm64/include/asm/kvm_host.h | 12 ++++--
>  arch/arm64/include/asm/kvm_hyp.h  |  1 +
>  arch/arm64/kvm/hyp/Makefile       |  1 -
>  arch/arm64/kvm/hyp/s2-setup.c     | 72 -------------------------------
>  arch/arm64/kvm/reset.c            | 35 +++++++++++++++
>  7 files changed, 45 insertions(+), 81 deletions(-)
>  delete mode 100644 arch/arm64/kvm/hyp/s2-setup.c
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 5f807b680a5f..14317b3a1820 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -135,8 +135,7 @@
>   * 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 102b5a5c47b6..0b53c72e7591 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 b04280ae1be0..5ecd457bce7d 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -61,11 +61,13 @@ struct kvm_arch {
>  	u64    vmid_gen;
>  	u32    vmid;
>  
> -	/* 1-level 2nd stage table, protected by kvm->mmu_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 +444,12 @@ 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 */
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index d1bd1e0f14d7..23aca66767f9 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -161,6 +161,7 @@ void __noreturn __hyp_do_panic(unsigned long, ...);
>   */
>  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/hyp/Makefile b/arch/arm64/kvm/hyp/Makefile
> index 2fabc2dc1966..82d1904328ad 100644
> --- a/arch/arm64/kvm/hyp/Makefile
> +++ b/arch/arm64/kvm/hyp/Makefile
> @@ -19,7 +19,6 @@ 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 e1ca672e937a..000000000000
> --- a/arch/arm64/kvm/hyp/s2-setup.c
> +++ /dev/null
> @@ -1,72 +0,0 @@
> -/*
> - * Copyright (C) 2016 - ARM Ltd
> - * Author: Marc Zyngier <marc.zyngier@....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/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index b0c07dab5cb3..616120c4176b 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -26,6 +26,7 @@
>  
>  #include <kvm/arm_arch_timer.h>
>  
> +#include <asm/cpufeature.h>
>  #include <asm/cputype.h>
>  #include <asm/ptrace.h>
>  #include <asm/kvm_arm.h>
> @@ -134,9 +135,43 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
>  	return kvm_timer_vcpu_reset(vcpu);
>  }
>  
> +/*
> + * 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, unsigned long type)
>  {
> +	u64 vtcr = VTCR_EL2_FLAGS;
> +	u32 parange, phys_shift;
> +
>  	if (type)
>  		return -EINVAL;
> +
> +	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;
> +
> +	phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
> +	if (phys_shift > KVM_PHYS_SHIFT)
> +		phys_shift = KVM_PHYS_SHIFT;
> +	vtcr |= VTCR_EL2_T0SZ(phys_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;
>  }
> 

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