Re: [GIT PULL 15/19] KVM: s390: Add skey emulation fault handling

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On 31.07.2018 10:44, Christian Borntraeger wrote:
> From: Janosch Frank <frankja@xxxxxxxxxxxxx>
> 
> When doing skey emulation for huge guests, we now need to fault in
> pmds, as we don't have PGSTES anymore to store them when we do not
> have valid table entries.
> 
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> ---
>  arch/s390/kvm/kvm-s390.c |  15 ++++--
>  arch/s390/kvm/priv.c     | 105 ++++++++++++++++++++++++++-------------
>  2 files changed, 83 insertions(+), 37 deletions(-)
> 
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 4cff5e31ca36..662f4d8046db 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1551,6 +1551,7 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
>  	uint8_t *keys;
>  	uint64_t hva;
>  	int srcu_idx, i, r = 0;
> +	bool unlocked;
>  
>  	if (args->flags != 0)
>  		return -EINVAL;
> @@ -1575,9 +1576,11 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
>  	if (r)
>  		goto out;
>  
> +	i = 0;
>  	down_read(&current->mm->mmap_sem);
>  	srcu_idx = srcu_read_lock(&kvm->srcu);
> -	for (i = 0; i < args->count; i++) {
> +        while (i < args->count) {
> +		unlocked = false;
>  		hva = gfn_to_hva(kvm, args->start_gfn + i);
>  		if (kvm_is_error_hva(hva)) {
>  			r = -EFAULT;
> @@ -1591,8 +1594,14 @@ static long kvm_s390_set_skeys(struct kvm *kvm, struct kvm_s390_skeys *args)
>  		}
>  
>  		r = set_guest_storage_key(current->mm, hva, keys[i], 0);
> -		if (r)
> -			break;
> +		if (r) {
> +			r = fixup_user_fault(current, current->mm, hva,
> +					     FAULT_FLAG_WRITE, &unlocked);
> +			if (r)
> +				break;
> +		}
> +		if (!r)
> +			i++;
>  	}
>  	srcu_read_unlock(&kvm->srcu, srcu_idx);
>  	up_read(&current->mm->mmap_sem);
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index eb0eb60c7be6..cfc5a62329f6 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -246,9 +246,10 @@ static int try_handle_skey(struct kvm_vcpu *vcpu)
>  
>  static int handle_iske(struct kvm_vcpu *vcpu)
>  {
> -	unsigned long addr;
> +	unsigned long gaddr, vmaddr;
>  	unsigned char key;
>  	int reg1, reg2;
> +	bool unlocked;
>  	int rc;
>  
>  	vcpu->stat.instruction_iske++;
> @@ -262,18 +263,28 @@ static int handle_iske(struct kvm_vcpu *vcpu)
>  
>  	kvm_s390_get_regs_rre(vcpu, &reg1, &reg2);
>  
> -	addr = vcpu->run->s.regs.gprs[reg2] & PAGE_MASK;
> -	addr = kvm_s390_logical_to_effective(vcpu, addr);
> -	addr = kvm_s390_real_to_abs(vcpu, addr);
> -	addr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(addr));
> -	if (kvm_is_error_hva(addr))
> +	gaddr = vcpu->run->s.regs.gprs[reg2] & PAGE_MASK;
> +	gaddr = kvm_s390_logical_to_effective(vcpu, gaddr);
> +	gaddr = kvm_s390_real_to_abs(vcpu, gaddr);
> +	vmaddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(gaddr));
> +	if (kvm_is_error_hva(vmaddr))
>  		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
> -
> +retry:
> +	unlocked = false;
>  	down_read(&current->mm->mmap_sem);
> -	rc = get_guest_storage_key(current->mm, addr, &key);
> -	up_read(&current->mm->mmap_sem);
> +	rc = get_guest_storage_key(current->mm, vmaddr, &key);
> +
> +	if (rc) {
> +		rc = fixup_user_fault(current, current->mm, vmaddr,
> +				      FAULT_FLAG_WRITE, &unlocked);
> +		if (!rc) {
> +			up_read(&current->mm->mmap_sem);
> +			goto retry;
> +		}
> +	}
>  	if (rc)
>  		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
> +	up_read(&current->mm->mmap_sem);
>  	vcpu->run->s.regs.gprs[reg1] &= ~0xff;
>  	vcpu->run->s.regs.gprs[reg1] |= key;
>  	return 0;
> @@ -281,8 +292,9 @@ static int handle_iske(struct kvm_vcpu *vcpu)
>  
>  static int handle_rrbe(struct kvm_vcpu *vcpu)
>  {
> -	unsigned long addr;
> +	unsigned long vmaddr, gaddr;
>  	int reg1, reg2;
> +	bool unlocked;
>  	int rc;
>  
>  	vcpu->stat.instruction_rrbe++;
> @@ -296,19 +308,27 @@ static int handle_rrbe(struct kvm_vcpu *vcpu)
>  
>  	kvm_s390_get_regs_rre(vcpu, &reg1, &reg2);
>  
> -	addr = vcpu->run->s.regs.gprs[reg2] & PAGE_MASK;
> -	addr = kvm_s390_logical_to_effective(vcpu, addr);
> -	addr = kvm_s390_real_to_abs(vcpu, addr);
> -	addr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(addr));
> -	if (kvm_is_error_hva(addr))
> +	gaddr = vcpu->run->s.regs.gprs[reg2] & PAGE_MASK;
> +	gaddr = kvm_s390_logical_to_effective(vcpu, gaddr);
> +	gaddr = kvm_s390_real_to_abs(vcpu, gaddr);
> +	vmaddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(gaddr));
> +	if (kvm_is_error_hva(vmaddr))
>  		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
> -
> +retry:
> +	unlocked = false;
>  	down_read(&current->mm->mmap_sem);
> -	rc = reset_guest_reference_bit(current->mm, addr);
> -	up_read(&current->mm->mmap_sem);
> +	rc = reset_guest_reference_bit(current->mm, vmaddr);
> +	if (rc < 0) {
> +		rc = fixup_user_fault(current, current->mm, vmaddr,
> +				      FAULT_FLAG_WRITE, &unlocked);
> +		if (!rc) {
> +			up_read(&current->mm->mmap_sem);
> +			goto retry;
> +		}
> +	}
>  	if (rc < 0)
>  		return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
> -
> +	up_read(&current->mm->mmap_sem);
>  	kvm_s390_set_psw_cc(vcpu, rc);
>  	return 0;
>  }
> @@ -323,6 +343,7 @@ static int handle_sske(struct kvm_vcpu *vcpu)
>  	unsigned long start, end;
>  	unsigned char key, oldkey;
>  	int reg1, reg2;
> +	bool unlocked;
>  	int rc;
>  
>  	vcpu->stat.instruction_sske++;
> @@ -355,19 +376,28 @@ static int handle_sske(struct kvm_vcpu *vcpu)
>  	}
>  
>  	while (start != end) {
> -		unsigned long addr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(start));
> +		unsigned long vmaddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(start));
> +		unlocked = false;
>  
> -		if (kvm_is_error_hva(addr))
> +		if (kvm_is_error_hva(vmaddr))
>  			return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>  
>  		down_read(&current->mm->mmap_sem);
> -		rc = cond_set_guest_storage_key(current->mm, addr, key, &oldkey,
> +		rc = cond_set_guest_storage_key(current->mm, vmaddr, key, &oldkey,
>  						m3 & SSKE_NQ, m3 & SSKE_MR,
>  						m3 & SSKE_MC);
> -		up_read(&current->mm->mmap_sem);
> -		if (rc < 0)
> +
> +		if (rc < 0) {
> +			rc = fixup_user_fault(current, current->mm, vmaddr,
> +					      FAULT_FLAG_WRITE, &unlocked);
> +			rc = !rc ? -EAGAIN : rc;
> +		}
> +		if (rc == -EFAULT)
>  			return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
> -		start += PAGE_SIZE;
> +
> +		up_read(&current->mm->mmap_sem);
> +		if (rc >= 0)
> +			start += PAGE_SIZE;
>  	}
>  
>  	if (m3 & (SSKE_MC | SSKE_MR)) {
> @@ -948,15 +978,16 @@ static int handle_pfmf(struct kvm_vcpu *vcpu)
>  	}
>  
>  	while (start != end) {
> -		unsigned long useraddr;
> +		unsigned long vmaddr;
> +		bool unlocked = false;
>  
>  		/* Translate guest address to host address */
> -		useraddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(start));
> -		if (kvm_is_error_hva(useraddr))
> +		vmaddr = gfn_to_hva(vcpu->kvm, gpa_to_gfn(start));
> +		if (kvm_is_error_hva(vmaddr))
>  			return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>  
>  		if (vcpu->run->s.regs.gprs[reg1] & PFMF_CF) {
> -			if (clear_user((void __user *)useraddr, PAGE_SIZE))
> +			if (clear_user((void __user *)vmaddr, PAGE_SIZE))
>  				return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
>  		}

What happened to the patch


commit 0230cae75df62de5813a4ca39a425ba439d036da
Author: Janosch Frank <frankja@xxxxxxxxxxxxx>
Date:   Wed Jul 4 15:50:01 2018 +0100

    KVM: s390: Replace clear_user with kvm_clear_guest
    
    kvm_clear_guest also does the dirty tracking for us, which we want to
    have.

?

-- 

Thanks,

David / dhildenb
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