Subject: [PATCH v5] arm64: fix VTTBR_BADDR_MASK

From: [email-masked] (Joel Schopp)
Date: Tue, 19 Aug 2014 09:23:57 -0500

On 08/19/2014 07:24 AM, Christoffer Dall wrote:
> On Mon, Aug 18, 2014 at 03:36:04PM -0500, 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
>> depend on hardware capability.
>>
>> According to Table D4-23 and Table D4-25 in ARM DDI 0487A.b document,
>> vttbr_x is calculated using different fixed values with consideration
>> of T0SZ, granule size and the level of translation tables. Therefore,
>> vttbr_baddr_mask should be determined dynamically.
>>
>> Changes since v4:
>> More minor cleanups from review
>> Moved some functions into headers
>>
>> Changes since v3:
>> Another rebase
>> Addressed minor comments from v2
>>
>> 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/include/asm/kvm_mmu.h   |   12 ++++++
>>  arch/arm/kvm/arm.c               |   17 +++++++-
>>  arch/arm64/include/asm/kvm_arm.h |   17 +-------
>>  arch/arm64/include/asm/kvm_mmu.h |   78 ++++++++++++++++++++++++++++++++++++++
>>  arch/arm64/kvm/hyp-init.S        |   20 +++++++---
>>  5 files changed, 122 insertions(+), 22 deletions(-)
>>
>> diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
>> index 5c7aa3c..73f6ff6 100644
>> --- a/arch/arm/include/asm/kvm_mmu.h
>> +++ b/arch/arm/include/asm/kvm_mmu.h
>> @@ -166,6 +166,18 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
>>  
>>  void stage2_flush_vm(struct kvm *kvm);
>>  
>> +static inline int kvm_get_phys_addr_shift(void)
>> +{
>> +	return KVM_PHYS_SHIFT;
>> +}
>> +
>> +static inline int set_vttbr_baddr_mask(void)
>> +{
>> +	vttbr_baddr_mask = VTTBR_BADDR_MASK;
>> +	return 0;
>> +}
>> +
>> +
>>  #endif	/* !__ASSEMBLY__ */
>>  
>>  #endif /* __ARM_KVM_MMU_H__ */
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index 3c82b37..f396eb7 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>
>> @@ -466,8 +467,14 @@ 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.
>> +	 */
>> +	BUG_ON(pgd_phys & ~vttbr_baddr_mask);
>> +
>> +	kvm->arch.vttbr = pgd_phys | vmid;
>>  
>>  	spin_unlock(&kvm_vmid_lock);
>>  }
>> @@ -1052,6 +1059,12 @@ 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 3d69030..8dbef70 100644
>> --- a/arch/arm64/include/asm/kvm_arm.h
>> +++ b/arch/arm64/include/asm/kvm_arm.h
>> @@ -94,7 +94,6 @@
>>  /* 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)
>> @@ -103,8 +102,6 @@
>>  #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)
>> @@ -119,36 +116,28 @@
>>  #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/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
>> index 7d29847..b6ae83b 100644
>> --- a/arch/arm64/include/asm/kvm_mmu.h
>> +++ b/arch/arm64/include/asm/kvm_mmu.h
>> @@ -152,5 +152,83 @@ static inline void coherent_cache_guest_page(struct kvm_vcpu *vcpu, hva_t hva,
>>  
>>  void stage2_flush_vm(struct kvm *kvm);
>>  
>> +/*
>> + * ARMv8 64K architecture limitations:
>> + * 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
>> + *
>> + * ARMv8 4K architecture limitations:
>> + * 16 <= T0SZ <= 24 is valid under 4 level of translation tables
>> + * 21 <= T0SZ <= 33 is valid under 3 level of translation tables
>> + * 30 <= T0SZ <= 39 is valid under 2 level of translation tables
>> + *
>> + * For 4K pages we only support 3 or 4 level, giving T0SZ a range of 16 to 33.
>> + * For 64K pages we only support 2 or 3 level, giving T0SZ a range of 16 to 34.
>> + *
>> + * 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
>> +static inline int t0sz_to_vttbr_x(int t0sz)
>> +{
>> +	if (t0sz < 16 || t0sz > 34) {
>> +		kvm_err("Cannot support %d-bit address space\n", 64 - t0sz);
>> +		return 0;
>> +	}
>> +
>> +	return 38 - t0sz;
>> +}
>> +#else /* 4K pages */
>> +static inline int t0sz_to_vttbr_x(int t0sz)
>> +{
>> +	if (t0sz < 16 || t0sz > 33) {
>> +		kvm_err("Cannot support %d-bit address space\n", 64 - t0sz);
>> +		return 0;
> why not just return an error code directly here?  These are now
> returning 0 on error which usually means everything was ok...
The return is a value,not just an error code. Because of this returning
an error overloads that value.  0 just seemed like a convenient invalid
value to check since a vttbr_x of 0 is invalid, but returning a negative
error code would be as equally invalid.  If this is the only issue it
doesn't seem worth respinning the patch for, but I'll change it to
-EINVAL if for some reason a v6 is needed.