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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: "Edgecombe, Rick P" <rick.p.edgecombe@intel.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"jmattson@google.com" <jmattson@google.com>,
	"peterz@infradead.org" <peterz@infradead.org>,
	"kirill.shutemov@linux.intel.com"
	<kirill.shutemov@linux.intel.com>,
	"Christopherson, Sean J" <sean.j.christopherson@intel.com>,
	"vkuznets@redhat.com" <vkuznets@redhat.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"x86@kernel.org" <x86@kernel.org>,
	"aarcange@redhat.com" <aarcange@redhat.com>,
	"keescook@chromium.org" <keescook@chromium.org>,
	"luto@kernel.org" <luto@kernel.org>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"rientjes@google.com" <rientjes@google.com>,
	"liran.alon@oracle.com" <liran.alon@oracle.com>,
	"rppt@kernel.org" <rppt@kernel.org>,
	"wad@chromium.org" <wad@chromium.org>,
	"wanpengli@tencent.com" <wanpengli@tencent.com>,
	"Kleen, Andi" <andi.kleen@intel.com>
Subject: Re: [RFCv2 14/16] KVM: Handle protected memory in __kvm_map_gfn()/__kvm_unmap_gfn()
Date: Fri, 23 Oct 2020 13:36:10 +0300	[thread overview]
Message-ID: <20201023103610.facpukoiodnj5v73@box> (raw)
In-Reply-To: <4df3bb56f56f5a8d69b4b288317111046158cebb.camel@intel.com>

On Thu, Oct 22, 2020 at 04:59:49PM +0000, Edgecombe, Rick P wrote:
> On Thu, 2020-10-22 at 15:06 +0300, Kirill A. Shutemov wrote:
> > > I think the page could have got unmapped since the gup via the
> > > hypercall on another CPU. It could be an avenue for the guest to
> > > crash
> > > the host.
> > 
> > Hm.. I'm not sure I follow. Could you elaborate on what scenario you
> > have
> > in mind?
> 
> Kind of similar scenario as the userspace triggered oops. My
> understanding is that the protected status was gathered along with the
> gup, but after the mm gets unlocked, nothing stops the page
> transitioning to unmapped(?). At which point kmap() from a previous gup
> with !protected, would go down the regular kmap() route and return an
> address to an unmapped page.
> 
> So the guest kernel could start with a page mapped as shared via the
> hypercall. Then trigger one of the PV MSR's that kmap() on CPU0. On
> CPU1, after the gup on CPU0, it could transitioned the page to
> private/unmapped via the hypercall. So the hva_to_pfn() would find
> !protected, but by the time the kmap() happened the page would have
> been unmapped. Am I missing something?

We need to fail protection enabling if a page is pinned. That's the only
option I see. But it might be pain to debug.

-- 
 Kirill A. Shutemov


  reply	other threads:[~2020-10-23 10:36 UTC|newest]

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-20  6:18 [RFCv2 00/16] KVM protected memory extension Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 01/16] x86/mm: Move force_dma_unencrypted() to common code Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 02/16] x86/kvm: Introduce KVM memory protection feature Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 03/16] x86/kvm: Make DMA pages shared Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 04/16] x86/kvm: Use bounce buffers for KVM memory protection Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 05/16] x86/kvm: Make VirtIO use DMA API in KVM guest Kirill A. Shutemov
2020-10-20  8:06   ` Christoph Hellwig
2020-10-20 12:47     ` Kirill A. Shutemov
2020-10-22  3:31   ` Halil Pasic
2020-10-20  6:18 ` [RFCv2 06/16] x86/kvmclock: Share hvclock memory with the host Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 07/16] x86/realmode: Share trampoline area if KVM memory protection enabled Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 08/16] KVM: Use GUP instead of copy_from/to_user() to access guest memory Kirill A. Shutemov
2020-10-20  8:25   ` John Hubbard
2020-10-20 12:51     ` Kirill A. Shutemov
2020-10-22 11:49     ` Matthew Wilcox
2020-10-22 19:58       ` John Hubbard
2020-10-26  4:21         ` Matthew Wilcox
2020-10-26  4:44           ` John Hubbard
2020-10-26 13:28             ` Matthew Wilcox
2020-10-26 14:16               ` Jason Gunthorpe
2020-10-26 20:52               ` John Hubbard
2020-10-20 17:29   ` Ira Weiny
2020-10-22 11:37     ` Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 09/16] KVM: mm: Introduce VM_KVM_PROTECTED Kirill A. Shutemov
2020-10-21 18:47   ` Edgecombe, Rick P
2020-10-22 12:01     ` Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 10/16] KVM: x86: Use GUP for page walk instead of __get_user() Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 11/16] KVM: Protected memory extension Kirill A. Shutemov
2020-10-20  7:17   ` Peter Zijlstra
2020-10-20 12:55     ` Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 12/16] KVM: x86: Enabled protected " Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 13/16] KVM: Rework copy_to/from_guest() to avoid direct mapping Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 14/16] KVM: Handle protected memory in __kvm_map_gfn()/__kvm_unmap_gfn() Kirill A. Shutemov
2020-10-21 18:50   ` Edgecombe, Rick P
2020-10-22 12:06     ` Kirill A. Shutemov
2020-10-22 16:59       ` Edgecombe, Rick P
2020-10-23 10:36         ` Kirill A. Shutemov [this message]
2020-10-22  3:26   ` Halil Pasic
2020-10-22 12:07     ` Kirill A. Shutemov
2020-10-20  6:18 ` [RFCv2 15/16] KVM: Unmap protected pages from direct mapping Kirill A. Shutemov
2020-10-20  7:12   ` Peter Zijlstra
2020-10-20 12:18   ` David Hildenbrand
2020-10-20 13:20     ` David Hildenbrand
2020-10-21  1:20       ` Edgecombe, Rick P
2020-10-26 19:55     ` Tom Lendacky
2020-10-21 18:49   ` Edgecombe, Rick P
2020-10-23 12:37   ` Mike Rapoport
2020-10-23 16:32     ` Sean Christopherson
2020-10-20  6:18 ` [RFCv2 16/16] mm: Do not use zero page for VM_KVM_PROTECTED VMAs Kirill A. Shutemov
2020-10-20  7:46 ` [RFCv2 00/16] KVM protected memory extension Vitaly Kuznetsov
2020-10-20 13:49   ` Kirill A. Shutemov
2020-10-21 14:46     ` Vitaly Kuznetsov
2020-10-23 11:35       ` Kirill A. Shutemov
2020-10-23 12:01         ` Vitaly Kuznetsov
2020-10-21 18:20 ` Andy Lutomirski
2020-10-26 15:29   ` Kirill A. Shutemov
2020-10-26 23:58     ` Andy Lutomirski

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