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

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On 03.08.2018 13:29, Christian Borntraeger wrote:
> 
> 
> 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
> 

Yes, but this patch does not respect 1/19. Cherry picking/applying the
patches one by one results and a conflict at this very spot.

As said, the final result (on the branch and merged) looks fine, but
looking at this series (including the branch) I have no clue where this
merge problem is actually resolved. I can neither spot it in this series
nor on the branch.

It's git magic.

-- 

Thanks,

David / dhildenb
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