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Date: Wed, 27 Aug 2014 12:07:11 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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To: Christian Borntraeger <borntraeger@de.ibm.com>,
	Ben Hutchings <ben@decadent.org.uk>
CC: KVM <kvm@vger.kernel.org>, Gleb Natapov <gleb@kernel.org>,
	Alexander Graf <agraf@suse.de>,
	Cornelia Huck <cornelia.huck@de.ibm.com>,
	Jens Freimann <jfrei@linux.vnet.ibm.com>,
	linux-s390 <linux-s390@vger.kernel.org>, stable@vger.kernel.org
Subject: Re: [GIT PULL 2/2] KVM: s390/mm: try a cow on read only pages for
 key ops
References: <1408972211-27122-1-git-send-email-borntraeger@de.ibm.com> <1408972211-27122-3-git-send-email-borntraeger@de.ibm.com> <1409108771.30127.21.camel@deadeye.wl.decadent.org.uk> <53FD8503.8040802@de.ibm.com>
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Il 27/08/2014 09:13, Christian Borntraeger ha scritto:
> On 27/08/14 05:06, Ben Hutchings wrote:
>> On Mon, 2014-08-25 at 15:10 +0200, Christian Borntraeger wrote:
>>> The PFMF instruction handler  blindly wrote the storage key even if
>>> the page was mapped R/O in the host. Lets try a COW before continuing
>>> and bail out in case of errors.
>>>
>>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> Reviewed-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
>>> Cc: stable@vger.kernel.org
>>> ---
>>>  arch/s390/mm/pgtable.c | 10 ++++++++++
>>>  1 file changed, 10 insertions(+)
>>>
>>> diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
>>> index 19daa53..5404a62 100644
>>> --- a/arch/s390/mm/pgtable.c
>>> +++ b/arch/s390/mm/pgtable.c
>>> @@ -986,11 +986,21 @@ int set_guest_storage_key(struct mm_struct *mm, unsigned long addr,
>>>  	pte_t *ptep;
>>>  
>>>  	down_read(&mm->mmap_sem);
>>> +retry:
>>>  	ptep = get_locked_pte(current->mm, addr, &ptl);
>>>  	if (unlikely(!ptep)) {
>>>  		up_read(&mm->mmap_sem);
>>>  		return -EFAULT;
>>>  	}
>>> +	if (!(pte_val(*ptep) & _PAGE_INVALID) &&
>>> +	     (pte_val(*ptep) & _PAGE_PROTECT)) {
>>> +			pte_unmap_unlock(*ptep, ptl);
>>> +			if (fixup_user_fault(current, mm, addr, FAULT_FLAG_WRITE)) {
>>> +				up_read(&mm->mmap_sem);
>>> +				return -EFAULT;
>>> +			}
>>> +			goto retry;
>>> +		}
>>
>> Every line below the first 'if' is indented one tab stop too far.
>>
>> Ben.
>>
>>>  	new = old = pgste_get_lock(ptep);
>>>  	pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |
>>
> 
> Hmm, indeed. Drat. Paolo, do you want a revert, resend?

Just send a trivial patch to fix up the formatting.

Paolo