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From: Janosch Frank <frankja@linux.ibm.com>
To: Janis Schoetterl-Glausch <scgl@linux.vnet.ibm.com>,
	David Hildenbrand <david@redhat.com>,
	Janis Schoetterl-Glausch <scgl@linux.ibm.com>,
	kvm@vger.kernel.org, borntraeger@de.ibm.com,
	imbrenda@linux.ibm.com, Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>
Cc: cohuck@redhat.com, linux-s390@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] KVM: s390: gaccess: Cleanup access to guest frames
Date: Thu, 19 Aug 2021 16:11:50 +0200	[thread overview]
Message-ID: <f98925f4-70f4-156b-0204-a50b2457de34@linux.ibm.com> (raw)
In-Reply-To: <745fb5fc-175b-5920-5c56-db4ca8bc2488@linux.vnet.ibm.com>

On 8/19/21 3:53 PM, Janis Schoetterl-Glausch wrote:
> On 8/18/21 10:06 AM, Janosch Frank wrote:
>> On 8/18/21 9:54 AM, David Hildenbrand wrote:
>>> On 16.08.21 17:07, Janis Schoetterl-Glausch wrote:
>>>> Introduce a helper function for guest frame access.
>>>> Rewrite the calculation of the gpa and the length of the segment
>>>> to be more readable.
>>>>
>>>> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
>> [...]
>>>> -	unsigned long _len, gpa;
>>>> +	unsigned long gpa;
>>>> +	unsigned int seg;
>>>>   	int rc = 0;
>>>>   
>>>>   	while (len && !rc) {
>>>>   		gpa = kvm_s390_real_to_abs(vcpu, gra);
>>>> -		_len = min(PAGE_SIZE - (gpa & ~PAGE_MASK), len);
>>>> -		if (mode)
>>>> -			rc = write_guest_abs(vcpu, gpa, data, _len);
>>>> -		else
>>>> -			rc = read_guest_abs(vcpu, gpa, data, _len);
>>>> -		len -= _len;
>>>> -		gra += _len;
>>>> -		data += _len;
>>>> +		seg = min(PAGE_SIZE - offset_in_page(gpa), len);
>>>
>>> What does "seg" mean? I certainly know when "len" means -- which is also 
>>> what the function eats.
>>
>> What does "_len" mean especially in contrast to "len"?
>>
>> "seg" is used in the common kvm guest access functions so it's at least
>> consistent although I share the sentiment that it's not a great name for
>> the length we access inside the page.
>>
>> Originally I suggested "len_in_page" if you have a better name I'd
>> expect we'll both be happy to discuss it :-)
> 
> fragment_len ? 

Sounds good to me

>>
>>>
>>>> +		rc = access_guest_frame(vcpu->kvm, mode, gpa, data, seg);
>>>> +		len -= seg;
>>>> +		gra += seg;
>>>> +		data += seg;
>>>>   	}
>>>>   	return rc;
>>>>   }
>>>>
>>>
>>>
>>
> 


  reply	other threads:[~2021-08-19 14:12 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210816150718.3063877-1-scgl@linux.ibm.com>
2021-08-16 15:07 ` Janis Schoetterl-Glausch
2021-08-18  7:46   ` Janosch Frank
2021-08-18  7:54   ` David Hildenbrand
2021-08-18  8:06     ` Janosch Frank
2021-08-18  8:44       ` David Hildenbrand
2021-08-18  8:48         ` Janis Schoetterl-Glausch
2021-08-19 13:53       ` Janis Schoetterl-Glausch
2021-08-19 14:11         ` Janosch Frank [this message]
2021-08-18  9:00     ` Janis Schoetterl-Glausch
2021-08-16 15:07 ` [PATCH 2/2] KVM: s390: gaccess: Refactor access address range check Janis Schoetterl-Glausch
2021-08-18 10:08   ` Claudio Imbrenda
2021-08-19 12:39     ` Janis Schoetterl-Glausch

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