From: David Hildenbrand <david@redhat.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>,
Janosch Frank <frankja@linux.vnet.ibm.com>
Cc: KVM <kvm@vger.kernel.org>, Cornelia Huck <cohuck@redhat.com>,
Thomas Huth <thuth@redhat.com>,
Ulrich Weigand <Ulrich.Weigand@de.ibm.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
linux-s390 <linux-s390@vger.kernel.org>,
Michael Mueller <mimu@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-mm@kvack.org
Subject: Re: [PATCH v2 05/42] s390/mm: provide memory management functions for protected KVM guests
Date: Mon, 17 Feb 2020 13:07:43 +0100 [thread overview]
Message-ID: <31c45ff8-a01a-6ec1-c169-9f52ace9f1f3@redhat.com> (raw)
In-Reply-To: <87742e00-9a8d-b7b4-ab96-05e8c9d39534@de.ibm.com>
>>> + if (local_drain) {
>>> + lru_add_drain_all();
>>
>> I do wonder if that is valid to be called with all the locks at this point.
>
> This function uses per cpu workers and needs no other locks. Also verified
> with lockdep.
Okay, perfect.
>>> +/**
>>> + * To be called with the page locked or with an extra reference!
>>
>> Can we have races here? (IOW, two callers concurrently for the same page)
>
> That would be fine and is part of the design. The ultravisor calls will
> either make the page accessible or will be a (mostly) no-op.
> In fact, we allow for slight over-indication of "needs to be exported"
>
> What about:
>
> /*
> * To be called with the page locked or with an extra reference! This will
> * prevent gmap_make_secure from touching the page concurrently. Having 2
> * parallel make_page_accessible is fine, as the UV calls will become a
> * no-op if the page is already exported.
> */
Yes, much clearer, thanks!
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-02-17 12:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-14 22:26 [PATCH v2 00/42] KVM: s390: Add support for protected VMs Christian Borntraeger
2020-02-14 22:26 ` [PATCH v2 01/42] mm:gup/writeback: add callbacks for inaccessible pages Christian Borntraeger
2020-02-17 9:14 ` David Hildenbrand
2020-02-17 11:10 ` Christian Borntraeger
2020-02-18 8:27 ` David Hildenbrand
2020-02-18 15:46 ` Sean Christopherson
2020-02-18 16:02 ` Will Deacon
2020-02-18 16:15 ` Christian Borntraeger
2020-02-18 21:35 ` Sean Christopherson
2020-02-19 8:31 ` David Hildenbrand
2020-02-14 22:26 ` [PATCH v2 05/42] s390/mm: provide memory management functions for protected KVM guests Christian Borntraeger
2020-02-17 10:21 ` David Hildenbrand
2020-02-17 11:28 ` Christian Borntraeger
2020-02-17 12:07 ` David Hildenbrand [this message]
2020-02-14 22:26 ` [PATCH v2 06/42] s390/mm: add (non)secure page access exceptions handlers Christian Borntraeger
2020-02-14 22:26 ` [PATCH v2 39/42] example for future extension: mm:gup/writeback: add callbacks for inaccessible pages: error cases Christian Borntraeger
2020-02-18 16:25 ` Will Deacon
2020-02-18 16:30 ` Christian Borntraeger
2020-02-18 16:33 ` Will Deacon
2020-02-14 22:26 ` [PATCH v2 40/42] example for future extension: mm:gup/writeback: add callbacks for inaccessible pages: source indication Christian Borntraeger
2020-02-17 14:15 ` Ulrich Weigand
2020-02-17 14:38 ` Christian Borntraeger
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