Subject: [PATCH v3] arm64: fix VTTBR_BADDR_MASK

From: [email-masked] (Joel Schopp)
Date: Mon, 4 Aug 2014 09:42:46 -0500

Since this fixes a real problem and didn't make it into 3.16 it would be
good if this made it into 3.17.

-Joel

On 08/04/2014 09:38 AM, Joel Schopp wrote:
> The current VTTBR_BADDR_MASK only masks 39 bits, which is broken on current
> systems.  Rather than just add a bit it seems like a good time to also set
> things at run-time instead of compile time to accomodate more hardware.
>
> This patch sets TCR_EL2.PS, VTCR_EL2.T0SZ and vttbr_baddr_mask in runtime,
> not compile time.
>
> In ARMv8, EL2 physical address size (TCR_EL2.PS) and stage2 input address
> size (VTCR_EL2.T0SZE) cannot be determined in compile time since they
> depends on hardware capability.
>
> According to Table D4-23 and Table D4-25 in ARM DDI 0487A.b document,
> vttbr_x is calculated using different hard-coded values with consideration
> of T0SZ, granule size and the level of translation tables. Therefore,
> vttbr_baddr_mask should be determined dynamically.
>
> Changes since v2:
> Rebased on https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git next branch
>
> Changes since v1:
> Rebased fix on Jungseok Lee's patch https://lkml.org/lkml/2014/5/12/189 to
> provide better long term fix.  Updated that patch to log error instead of
> silently fail on unaligned vttbr.
>
> Cc: Christoffer Dall <[email-masked]>
> Cc: Sungjinn Chung <[email-masked]>
> Signed-off-by: Jungseok Lee <[email-masked]>
> Signed-off-by: Joel Schopp <[email-masked]>
> ---
>  arch/arm/kvm/arm.c               |   91 +++++++++++++++++++++++++++++++++++++-
>  arch/arm64/include/asm/kvm_arm.h |   17 +------
>  arch/arm64/kvm/hyp-init.S        |   20 ++++++--
>  3 files changed, 106 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index d7424ef..d7ca2f5 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -37,6 +37,7 @@
>  #include <asm/mman.h>
>  #include <asm/tlbflush.h>
>  #include <asm/cacheflush.h>
> +#include <asm/cputype.h>
>  #include <asm/virt.h>
>  #include <asm/kvm_arm.h>
>  #include <asm/kvm_asm.h>
> @@ -61,6 +62,9 @@ static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
>  static u8 kvm_next_vmid;
>  static DEFINE_SPINLOCK(kvm_vmid_lock);
>  
> +/* VTTBR mask cannot be determined in complie time under ARMv8 */
> +static u64 vttbr_baddr_mask;
> +
>  static bool vgic_present;
>  
>  static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
> @@ -376,6 +380,75 @@ static bool need_new_vmid_gen(struct kvm *kvm)
>  }
>  
>  /**
> + * set_vttbr_baddr_mask - set mask value for vttbr base address
> + *
> + * In ARMv8, vttbr_baddr_mask cannot be determined in compile time since stage2
> + * input address size depends on hardware capability. Thus, it is needed to read
> + * ID_AA64MMFR0_EL1.PARange first and then set vttbr_baddr_mask with
> + * consideration of both granule size and the level of translation tables.
> + */
> +static int set_vttbr_baddr_mask(void)
> +{
> +#ifndef CONFIG_ARM64
> +	vttbr_baddr_mask = VTTBR_BADDR_MASK;
> +#else
> +	int pa_range, t0sz, vttbr_x;
> +
> +	pa_range = read_cpuid(ID_AA64MMFR0_EL1) & 0xf;
> +
> +	switch (pa_range) {
> +	case 0:
> +		t0sz = VTCR_EL2_T0SZ(32);
> +		break;
> +	case 1:
> +		t0sz = VTCR_EL2_T0SZ(36);
> +		break;
> +	case 2:
> +		t0sz = VTCR_EL2_T0SZ(40);
> +		break;
> +	case 3:
> +		t0sz = VTCR_EL2_T0SZ(42);
> +		break;
> +	case 4:
> +		t0sz = VTCR_EL2_T0SZ(44);
> +		break;
> +	default:
> +		t0sz = VTCR_EL2_T0SZ(48);
> +	}
> +
> +	/*
> +	 * See Table D4-23 and Table D4-25 in ARM DDI 0487A.b to figure out
> +	 * the origin of the hardcoded values, 38 and 37.
> +	 */
> +#ifdef CONFIG_ARM64_64K_PAGES
> +	/*
> +	 * 16 <= T0SZ <= 21 is valid under 3 level of translation tables
> +	 * 18 <= T0SZ <= 34 is valid under 2 level of translation tables
> +	 * 31 <= T0SZ <= 39 is valid under 1 level of transltaion tables
> +	 */
> +	if (t0sz <= 17) {
> +		kvm_err("Cannot support %d-bit address space\n", 64 - t0sz);
> +		return -EINVAL;
> +	}
> +	vttbr_x = 38 - t0sz;
> +#else
> +	/*
> +	 * 16 <= T0SZ <= 24 is valid under 4 level of translation tables
> +	 * 21 <= T0SZ <= 30 is valid under 3 level of translation tables
> +	 * 30 <= T0SZ <= 39 is valid under 2 level of translation tables
> +	 */
> +	if (t0sz <= 20) {
> +		kvm_err("Cannot support %d-bit address space\n", 64 - t0sz);
> +		return -EINVAL;
> +	}
> +	vttbr_x = 37 - t0sz;
> +#endif
> +	vttbr_baddr_mask = (((1LLU << (48 - vttbr_x)) - 1) << (vttbr_x - 1));
> +#endif
> +	return 0;
> +}
> +
> +/**
>   * update_vttbr - Update the VTTBR with a valid VMID before the guest runs
>   * @kvm	The guest that we are about to run
>   *
> @@ -429,8 +502,16 @@ static void update_vttbr(struct kvm *kvm)
>  	/* update vttbr to be used with the new vmid */
>  	pgd_phys = virt_to_phys(kvm->arch.pgd);
>  	vmid = ((u64)(kvm->arch.vmid) << VTTBR_VMID_SHIFT) & VTTBR_VMID_MASK;
> -	kvm->arch.vttbr = pgd_phys & VTTBR_BADDR_MASK;
> -	kvm->arch.vttbr |= vmid;
> +
> +	/*
> +	 * If the VTTBR isn't aligned there is something wrong with the system
> +	 * or kernel.  It is better to just fail and not mask it. But no need
> +	 * to panic the host kernel with a BUG_ON(), instead just log the error.
> +	 */
> +	if (pgd_phys & ~vttbr_baddr_mask)
> +		kvm_err("VTTBR not aligned, expect guest to fail");
> +
> +	kvm->arch.vttbr = pgd_phys | vmid;
>  
>  	spin_unlock(&kvm_vmid_lock);
>  }
> @@ -1015,6 +1096,12 @@ int kvm_arch_init(void *opaque)
>  		}
>  	}
>  
> +	err = set_vttbr_baddr_mask();
> +	if (err) {
> +		kvm_err("Cannot set vttbr_baddr_mask\n");
> +		return -EINVAL;
> +	}
> +
>  	cpu_notifier_register_begin();
>  
>  	err = init_hyp_mode();
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index cc83520..ff4a4fa 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -95,7 +95,6 @@
>  /* TCR_EL2 Registers bits */
>  #define TCR_EL2_TBI	(1 << 20)
>  #define TCR_EL2_PS	(7 << 16)
> -#define TCR_EL2_PS_40B	(2 << 16)
>  #define TCR_EL2_TG0	(1 << 14)
>  #define TCR_EL2_SH0	(3 << 12)
>  #define TCR_EL2_ORGN0	(3 << 10)
> @@ -104,8 +103,6 @@
>  #define TCR_EL2_MASK	(TCR_EL2_TG0 | TCR_EL2_SH0 | \
>  			 TCR_EL2_ORGN0 | TCR_EL2_IRGN0 | TCR_EL2_T0SZ)
>  
> -#define TCR_EL2_FLAGS	(TCR_EL2_PS_40B)
> -
>  /* VTCR_EL2 Registers bits */
>  #define VTCR_EL2_PS_MASK	(7 << 16)
>  #define VTCR_EL2_TG0_MASK	(1 << 14)
> @@ -120,36 +117,28 @@
>  #define VTCR_EL2_SL0_MASK	(3 << 6)
>  #define VTCR_EL2_SL0_LVL1	(1 << 6)
>  #define VTCR_EL2_T0SZ_MASK	0x3f
> -#define VTCR_EL2_T0SZ_40B	24
> +#define VTCR_EL2_T0SZ(bits)	(64 - (bits))
>  
>  #ifdef CONFIG_ARM64_64K_PAGES
>  /*
>   * Stage2 translation configuration:
> - * 40bits output (PS = 2)
> - * 40bits input  (T0SZ = 24)
>   * 64kB pages (TG0 = 1)
>   * 2 level page tables (SL = 1)
>   */
>  #define VTCR_EL2_FLAGS		(VTCR_EL2_TG0_64K | VTCR_EL2_SH0_INNER | \
>  				 VTCR_EL2_ORGN0_WBWA | VTCR_EL2_IRGN0_WBWA | \
> -				 VTCR_EL2_SL0_LVL1 | VTCR_EL2_T0SZ_40B)
> -#define VTTBR_X		(38 - VTCR_EL2_T0SZ_40B)
> +				 VTCR_EL2_SL0_LVL1)
>  #else
>  /*
>   * Stage2 translation configuration:
> - * 40bits output (PS = 2)
> - * 40bits input  (T0SZ = 24)
>   * 4kB pages (TG0 = 0)
>   * 3 level page tables (SL = 1)
>   */
>  #define VTCR_EL2_FLAGS		(VTCR_EL2_TG0_4K | VTCR_EL2_SH0_INNER | \
>  				 VTCR_EL2_ORGN0_WBWA | VTCR_EL2_IRGN0_WBWA | \
> -				 VTCR_EL2_SL0_LVL1 | VTCR_EL2_T0SZ_40B)
> -#define VTTBR_X		(37 - VTCR_EL2_T0SZ_40B)
> +				 VTCR_EL2_SL0_LVL1)
>  #endif
>  
> -#define VTTBR_BADDR_SHIFT (VTTBR_X - 1)
> -#define VTTBR_BADDR_MASK  (((1LLU << (40 - VTTBR_X)) - 1) << VTTBR_BADDR_SHIFT)
>  #define VTTBR_VMID_SHIFT  (48LLU)
>  #define VTTBR_VMID_MASK	  (0xffLLU << VTTBR_VMID_SHIFT)
>  
> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
> index d968796..c0f7634 100644
> --- a/arch/arm64/kvm/hyp-init.S
> +++ b/arch/arm64/kvm/hyp-init.S
> @@ -63,17 +63,21 @@ __do_hyp_init:
>  	mrs	x4, tcr_el1
>  	ldr	x5, =TCR_EL2_MASK
>  	and	x4, x4, x5
> -	ldr	x5, =TCR_EL2_FLAGS
> -	orr	x4, x4, x5
> -	msr	tcr_el2, x4
> -
> -	ldr	x4, =VTCR_EL2_FLAGS
>  	/*
>  	 * Read the PARange bits from ID_AA64MMFR0_EL1 and set the PS bits in
> -	 * VTCR_EL2.
> +	 * TCR_EL2 and both PS bits and T0SZ bits in VTCR_EL2.
>  	 */
>  	mrs	x5, ID_AA64MMFR0_EL1
>  	bfi	x4, x5, #16, #3
> +	msr	tcr_el2, x4
> +
> +	ldr	x4, =VTCR_EL2_FLAGS
> +	bfi	x4, x5, #16, #3
> +	and	x5, x5, #0xf
> +	adr	x6, t0sz
> +	add	x6, x6, x5, lsl #2
> +	ldr	w5, [x6]
> +	orr	x4, x4, x5
>  	msr	vtcr_el2, x4
>  
>  	mrs	x4, mair_el1
> @@ -109,6 +113,10 @@ target: /* We're now in the trampoline code, switch page tables */
>  
>  	/* Hello, World! */
>  	eret
> +
> +t0sz:
> +	.word	VTCR_EL2_T0SZ(32), VTCR_EL2_T0SZ(36), VTCR_EL2_T0SZ(40)
> +	.word	VTCR_EL2_T0SZ(42), VTCR_EL2_T0SZ(44), VTCR_EL2_T0SZ(48)
>  ENDPROC(__kvm_hyp_init)
>  
>  	.ltorg
>