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

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On 08/02/2018 11:01 AM, David Hildenbrand wrote:
> 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.

Patch 1/19

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