From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Janosch Frank <frankja@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Marc Zyngier <maz@kernel.org>,
Tom Lendacky <thomas.lendacky@amd.com>, KVM <kvm@vger.kernel.org>,
Cornelia Huck <cohuck@redhat.com>,
David Hildenbrand <david@redhat.com>,
Thomas Huth <thuth@redhat.com>,
Ulrich Weigand <Ulrich.Weigand@de.ibm.com>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Andrea Arcangeli <aarcange@redhat.com>,
linux-s390 <linux-s390@vger.kernel.org>,
Michael Mueller <mimu@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
linux-mm@kvack.org, kvm-ppc@vger.kernel.org,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH 01/35] mm:gup/writeback: add callbacks for inaccessible pages
Date: Thu, 13 Feb 2020 12:46:28 -0800 [thread overview]
Message-ID: <20200213204628.GE18610@linux.intel.com> (raw)
In-Reply-To: <e2c41b25-6d6d-6685-3450-2e3e8d84efd1@de.ibm.com>
On Thu, Feb 13, 2020 at 09:13:35PM +0100, Christian Borntraeger wrote:
>
> On 13.02.20 20:56, Sean Christopherson wrote:
> > On Mon, Feb 10, 2020 at 06:27:04PM +0100, Christian Borntraeger wrote:
> > Am I missing a need to do this for the swap/reclaim case? Or is there a
> > completely different use case I'm overlooking?
>
> This is actually to protect the host against a malicious user space. For
> example a bad QEMU could simply start direct I/O on such protected memory.
> We do not want userspace to be able to trigger I/O errors and thus we
> implemented the logic to "whenever somebody accesses that page (gup) or
> doing I/O, make sure that this page can be accessed. When the guest tries
> to access that page we will wait in the page fault handler for writeback to
> have finished and for the page_ref to be the expected value.
Ah. I was assuming the pages would unmappable by userspace, enforced by
some other mechanism
> >
> > Tangentially related, hooks here could be quite useful for sanity checking
> > the kernel/KVM and/or debugging kernel/KVM bugs. Would it make sense to
> > pass a param to arch_make_page_accessible() to provide some information as
> > to why the page needs to be made accessible?
>
> Some kind of enum that can be used optionally to optimize things?
Not just optimize, in the case above it'd probably preferable for us to
reject a userspace mapping outright, e.g. return -EFAULT if called from
gup()/follow(). Debug scenarios might also require differentiating between
writeback and "other".
next prev parent reply other threads:[~2020-02-13 20:46 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-07 11:39 [PATCH 00/35] KVM: s390: Add support for protected VMs Christian Borntraeger
2020-02-07 11:39 ` [PATCH 01/35] mm:gup/writeback: add callbacks for inaccessible pages Christian Borntraeger
2020-02-10 17:27 ` Christian Borntraeger
2020-02-11 11:26 ` Will Deacon
2020-02-11 11:43 ` Christian Borntraeger
2020-02-13 14:48 ` Christian Borntraeger
2020-02-18 16:02 ` Will Deacon
2020-02-13 19:56 ` Sean Christopherson
2020-02-13 20:13 ` Christian Borntraeger
2020-02-13 20:46 ` Sean Christopherson [this message]
2020-02-17 20:55 ` Tom Lendacky
2020-02-17 21:14 ` Christian Borntraeger
2020-02-10 18:17 ` David Hildenbrand
2020-02-10 18:28 ` Christian Borntraeger
2020-02-10 18:43 ` David Hildenbrand
2020-02-10 18:51 ` Christian Borntraeger
2020-02-18 3:36 ` Tian, Kevin
2020-02-18 6:44 ` Christian Borntraeger
2020-02-07 11:39 ` [PATCH 02/35] KVM: s390/interrupt: do not pin adapter interrupt pages Christian Borntraeger
2020-02-10 12:26 ` David Hildenbrand
2020-02-10 18:38 ` Christian Borntraeger
2020-02-10 19:33 ` David Hildenbrand
2020-02-11 9:23 ` [PATCH v2 RFC] " Christian Borntraeger
2020-02-12 11:52 ` Christian Borntraeger
2020-02-12 12:16 ` David Hildenbrand
2020-02-12 12:22 ` Christian Borntraeger
2020-02-12 12:47 ` David Hildenbrand
2020-02-12 12:39 ` Cornelia Huck
2020-02-12 12:44 ` Christian Borntraeger
2020-02-12 13:07 ` Cornelia Huck
2020-02-10 18:56 ` [PATCH 02/35] KVM: s390/interrupt: do not pin adapter interrupt Ulrich Weigand
2020-02-10 12:40 ` [PATCH 02/35] KVM: s390/interrupt: do not pin adapter interrupt pages David Hildenbrand
2020-02-07 11:39 ` [PATCH 05/35] s390/mm: provide memory management functions for protected KVM guests Christian Borntraeger
2020-02-12 13:42 ` Cornelia Huck
2020-02-13 7:43 ` Christian Borntraeger
2020-02-13 8:44 ` Cornelia Huck
2020-02-14 17:59 ` David Hildenbrand
2020-02-14 21:17 ` Christian Borntraeger
2020-02-07 11:39 ` [PATCH 06/35] s390/mm: add (non)secure page access exceptions handlers Christian Borntraeger
2020-02-14 18:05 ` David Hildenbrand
2020-02-14 19:59 ` Christian Borntraeger
2020-02-07 11:39 ` [PATCH 10/35] KVM: s390: protvirt: Secure memory is not mergeable Christian Borntraeger
2020-02-07 11:39 ` [PATCH 11/35] KVM: s390/mm: Make pages accessible before destroying the guest Christian Borntraeger
2020-02-14 18:40 ` David Hildenbrand
2020-02-07 11:39 ` [PATCH 21/35] KVM: s390/mm: handle guest unpin events Christian Borntraeger
2020-02-10 14:58 ` Thomas Huth
2020-02-11 13:21 ` Cornelia Huck
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