Subject: Re: [PATCH v4 05/15] KVM: arm64: Export kvm_handle_user_mem_abort()
To:     Gavin Shan <gshan@redhat.com>, kvmarm@lists.cs.columbia.edu
Cc:     linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        james.morse@arm.com, mark.rutland@arm.com,
        Jonathan.Cameron@huawei.com, will@kernel.org, maz@kernel.org,
        pbonzini@redhat.com, vkuznets@redhat.com, shan.gavin@gmail.com
References: <20210815005947.83699-1-gshan@redhat.com>
 <20210815005947.83699-6-gshan@redhat.com>
From:   Eric Auger <eauger@redhat.com>
Message-ID: <53a578a1-6005-8e66-dda1-bd75d3a6f264@redhat.com>
Date:   Wed, 10 Nov 2021 19:02:33 +0100
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Hi Gavin,
On 8/15/21 2:59 AM, Gavin Shan wrote:
> The main work of stage-2 page fault is handled by user_mem_abort().
> When asynchronous page fault is supported, one page fault need to
> be handled with two calls to this function. It means the page fault
> needs to be replayed asynchronously in that case.
> 
>    * This renames the function to kvm_handle_user_mem_abort() and
>      exports it.
> 
>    * Add arguments @esr and @prefault to user_mem_abort(). @esr is
>      the cached value of ESR_EL2 instead of fetching from the current
>      vCPU when the page fault is replayed in scenario of asynchronous
>      page fault. @prefault is used to indicate the page fault is replayed
>      one or not.
Also explain that fault_status arg is not needed anymore as derived from
@esr because otherwise at first sight a distracted reviewer like me may
have the impression you replaced fault_status by prefault while it is
totally unrelated
> 
>    * Define helper functions esr_dbat_*() in asm/esr.h to extract
>      or check various fields of the passed ESR_EL2 value because
>      those helper functions defined in asm/kvm_emulate.h assumes
>      the ESR_EL2 value has been cached in vCPU struct. It won't
>      be true on handling the replayed page fault in scenario of
>      asynchronous page fault.
I would introduce a seperate preliminary patch with those esr macros and
changes to the call sites + changes below.
> 
>    * Some helper functions defined in asm/kvm_emulate.h are used
>      by mmu.c only and seem not to be used by other source file
>      in near future. They are moved to mmu.c and renamed accordingly.>
>      is_exec_fault: kvm_vcpu_trap_is_exec_fault
>      is_write_fault: kvm_is_write_fault()
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  arch/arm64/include/asm/esr.h         |  6 ++++
>  arch/arm64/include/asm/kvm_emulate.h | 27 ++---------------
>  arch/arm64/include/asm/kvm_host.h    |  4 +++
>  arch/arm64/kvm/mmu.c                 | 43 ++++++++++++++++++++++------
>  4 files changed, 48 insertions(+), 32 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
> index 29f97eb3dad4..0f2cb27691de 100644
> --- a/arch/arm64/include/asm/esr.h
> +++ b/arch/arm64/include/asm/esr.h
> @@ -321,8 +321,14 @@
>  					 ESR_ELx_CP15_32_ISS_DIR_READ)
>  
>  #ifndef __ASSEMBLY__
> +#include <linux/bitfield.h>
>  #include <asm/types.h>
>  
> +#define esr_dabt_fault_type(esr)	(esr & ESR_ELx_FSC_TYPE)
> +#define esr_dabt_fault_level(esr)	(FIELD_GET(ESR_ELx_FSC_LEVEL, esr))
> +#define esr_dabt_is_wnr(esr)		(!!(FIELD_GET(ESR_ELx_WNR, esr)))
> +#define esr_dabt_is_s1ptw(esr)		(!!(FIELD_GET(ESR_ELx_S1PTW, esr)))
> +
>  static inline bool esr_is_data_abort(u32 esr)
>  {
>  	const u32 ec = ESR_ELx_EC(esr);
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 923b4d08ea9a..90742f4b1acd 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -285,13 +285,13 @@ static __always_inline int kvm_vcpu_dabt_get_rd(const struct kvm_vcpu *vcpu)
>  
>  static __always_inline bool kvm_vcpu_abt_iss1tw(const struct kvm_vcpu *vcpu)
>  {
> -	return !!(kvm_vcpu_get_esr(vcpu) & ESR_ELx_S1PTW);
> +	return esr_dabt_is_s1ptw(kvm_vcpu_get_esr(vcpu));
>  }
>  
>  /* Always check for S1PTW *before* using this. */
>  static __always_inline bool kvm_vcpu_dabt_iswrite(const struct kvm_vcpu *vcpu)
>  {
> -	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_WNR;
> +	return esr_dabt_is_wnr(kvm_vcpu_get_esr(vcpu));
>  }
>  
>  static inline bool kvm_vcpu_dabt_is_cm(const struct kvm_vcpu *vcpu)
> @@ -320,11 +320,6 @@ static inline bool kvm_vcpu_trap_is_iabt(const struct kvm_vcpu *vcpu)
>  	return kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_IABT_LOW;
>  }
>  
> -static inline bool kvm_vcpu_trap_is_exec_fault(const struct kvm_vcpu *vcpu)
> -{
> -	return kvm_vcpu_trap_is_iabt(vcpu) && !kvm_vcpu_abt_iss1tw(vcpu);
> -}
> -
>  static __always_inline u8 kvm_vcpu_trap_get_fault(const struct kvm_vcpu *vcpu)
>  {
>  	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC;
> @@ -332,12 +327,7 @@ static __always_inline u8 kvm_vcpu_trap_get_fault(const struct kvm_vcpu *vcpu)
>  
>  static __always_inline u8 kvm_vcpu_trap_get_fault_type(const struct kvm_vcpu *vcpu)
>  {
> -	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_TYPE;
> -}
> -
> -static __always_inline u8 kvm_vcpu_trap_get_fault_level(const struct kvm_vcpu *vcpu)
> -{
> -	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_LEVEL;
> +	return esr_dabt_fault_type(kvm_vcpu_get_esr(vcpu));
>  }
>  
>  static __always_inline bool kvm_vcpu_abt_issea(const struct kvm_vcpu *vcpu)
> @@ -365,17 +355,6 @@ static __always_inline int kvm_vcpu_sys_get_rt(struct kvm_vcpu *vcpu)
>  	return ESR_ELx_SYS64_ISS_RT(esr);
>  }
>  
> -static inline bool kvm_is_write_fault(struct kvm_vcpu *vcpu)
> -{
> -	if (kvm_vcpu_abt_iss1tw(vcpu))
> -		return true;
> -
> -	if (kvm_vcpu_trap_is_iabt(vcpu))
> -		return false;
> -
> -	return kvm_vcpu_dabt_iswrite(vcpu);
> -}
> -
>  static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
>  {
>  	return vcpu_read_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 1824f7e1f9ab..581825b9df77 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -606,6 +606,10 @@ int __kvm_arm_vcpu_set_events(struct kvm_vcpu *vcpu,
>  
>  #define KVM_ARCH_WANT_MMU_NOTIFIER
>  
> +int kvm_handle_user_mem_abort(struct kvm_vcpu *vcpu,
> +			      struct kvm_memory_slot *memslot,
> +			      phys_addr_t fault_ipa, unsigned long hva,
> +			      unsigned int esr, bool prefault);
>  void kvm_arm_halt_guest(struct kvm *kvm);
>  void kvm_arm_resume_guest(struct kvm *kvm);
>  
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 0625bf2353c2..e4038c5e931d 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -892,9 +892,34 @@ static int sanitise_mte_tags(struct kvm *kvm, kvm_pfn_t pfn,
>  	return 0;
>  }
>  
> -static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> -			  struct kvm_memory_slot *memslot, unsigned long hva,
> -			  unsigned long fault_status)
> +static inline bool is_exec_fault(unsigned int esr)
> +{
> +	if (ESR_ELx_EC(esr) != ESR_ELx_EC_IABT_LOW)
> +		return false;
> +
> +	if (esr_dabt_is_s1ptw(esr))
> +		return false;
> +
> +	return true;
> +}
> +
> +static inline bool is_write_fault(unsigned int esr)
> +{
> +	if (esr_dabt_is_s1ptw(esr))
> +		return true;
> +
> +	if (ESR_ELx_EC(esr) == ESR_ELx_EC_IABT_LOW)
> +		return false;
> +
> +	return esr_dabt_is_wnr(esr);
> +}
> +
> +int kvm_handle_user_mem_abort(struct kvm_vcpu *vcpu,
> +			      struct kvm_memory_slot *memslot,
> +			      phys_addr_t fault_ipa,
> +			      unsigned long hva,
> +			      unsigned int esr,
> +			      bool prefault)
you added the prefault arg but this latter is not used in the function?
To me you shall introduce that change in a subsequent patch when relevant.
>  {
>  	int ret = 0;
>  	bool write_fault, writable, force_pte = false;
> @@ -909,14 +934,15 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>  	gfn_t gfn;
>  	kvm_pfn_t pfn;
>  	bool logging_active = memslot_is_logging(memslot);
> -	unsigned long fault_level = kvm_vcpu_trap_get_fault_level(vcpu);
> +	unsigned int fault_status = esr_dabt_fault_type(esr);
> +	unsigned long fault_level = esr_dabt_fault_level(esr);
>  	unsigned long vma_pagesize, fault_granule;
>  	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;
>  	struct kvm_pgtable *pgt;
>  
>  	fault_granule = 1UL << ARM64_HW_PGTABLE_LEVEL_SHIFT(fault_level);
> -	write_fault = kvm_is_write_fault(vcpu);
> -	exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu);
> +	write_fault = is_write_fault(kvm_vcpu_get_esr(vcpu));
> +	exec_fault = is_exec_fault(kvm_vcpu_get_esr(vcpu));
>  	VM_BUG_ON(write_fault && exec_fault);
>  
>  	if (fault_status == FSC_PERM && !write_fault && !exec_fault) {
> @@ -1176,7 +1202,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
>  	gfn = fault_ipa >> PAGE_SHIFT;
>  	memslot = gfn_to_memslot(vcpu->kvm, gfn);
>  	hva = gfn_to_hva_memslot_prot(memslot, gfn, &writable);
> -	write_fault = kvm_is_write_fault(vcpu);
> +	write_fault = is_write_fault(kvm_vcpu_get_esr(vcpu));
>  	if (kvm_is_error_hva(hva) || (write_fault && !writable)) {
>  		/*
>  		 * The guest has put either its instructions or its page-tables
> @@ -1231,7 +1257,8 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
>  		goto out_unlock;
>  	}
>  
> -	ret = user_mem_abort(vcpu, fault_ipa, memslot, hva, fault_status);
> +	ret = kvm_handle_user_mem_abort(vcpu, memslot, fault_ipa, hva,
> +					kvm_vcpu_get_esr(vcpu), false);>  	if (ret == 0)
>  		ret = 1;
>  out:
> 
Thanks

Eric