From: Marcelo Tosatti <mtosatti@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v5 00/12] KVM: introduce readonly memslot
Date: Wed, 15 Aug 2012 14:53:39 -0300 [thread overview]
Message-ID: <20120815175338.GA18452@amt.cnet> (raw)
In-Reply-To: <502B7D7E.20902@redhat.com>
On Wed, Aug 15, 2012 at 01:44:14PM +0300, Avi Kivity wrote:
> On 08/14/2012 06:51 PM, Marcelo Tosatti wrote:
> >>
> >> Userspace may want to modify the ROM (for example, when programming a
> >> flash device). It is also possible to map an hva range rw through one
> >> slot and ro through another.
> >
> > Right, can do that with multiple userspace maps to the same anonymous
> > memory region (see other email).
>
> Yes it's possible. It requires that we move all memory allocation to be
> fd based, since userspace can't predict what memory will be dual-mapped
> (at least if emulated hardware allows this).
It can:
- Create named memory object, with associated fd.
- Copy data from large anonymous memory region to named memory.
- Unmap region that must be dual-mapped from large anonymous memory chunk.
- Map named memory object at address.
The last step can be replaced by adjusting KVM memory slots.
The disadvantage of protection information in memory slots
is that it duplicates functionality that is handled by
userspace mappings.
Moreover, multiple memory maps are necessary for any
split-qemu-into-smaller-pieces solutions.
> Is this a reasonable
> requirement? Do ksm/thp/autonuma work with this?
As mentioned, only memory used for ROM purposes must be dual mapped.
I don't think there is any way to create multiple mappings
to one anonymous memory object ATM, but POSIX defines it
(posix_typed_mem_open).
The limitation of thp/ksm on shared memory also affects any other user
of shared memory, so it should be fixed there.
Also, QEMU ROM is allocated separately from RAM, correct?
next prev parent reply other threads:[~2012-08-15 18:00 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-07 9:47 [PATCH v5 00/12] KVM: introduce readonly memslot Xiao Guangrong
2012-08-07 9:48 ` [PATCH v5 01/12] KVM: fix missing check for memslot flags Xiao Guangrong
2012-08-07 9:48 ` [PATCH v5 02/12] KVM: hide KVM_MEMSLOT_INVALID from userspace Xiao Guangrong
2012-08-09 18:48 ` Marcelo Tosatti
2012-08-10 2:11 ` Xiao Guangrong
2012-08-07 9:49 ` [PATCH v5 03/12] KVM: introduce gfn_to_pfn_memslot_atomic Xiao Guangrong
2012-08-09 18:50 ` Marcelo Tosatti
2012-08-10 3:22 ` Xiao Guangrong
2012-08-07 9:50 ` [PATCH v5 04/12] KVM: introduce gfn_to_hva_read/kvm_read_hva/kvm_read_hva_atomic Xiao Guangrong
2012-08-07 9:51 ` [PATCH v5 05/12] KVM: reorganize hva_to_pfn Xiao Guangrong
2012-08-10 17:51 ` Marcelo Tosatti
2012-08-11 3:11 ` Xiao Guangrong
2012-08-07 9:51 ` [PATCH v5 06/12] KVM: use 'writable' as a hint to map writable pfn Xiao Guangrong
2012-08-07 9:52 ` [PATCH v5 07/12] KVM: introduce KVM_PFN_ERR_RO_FAULT Xiao Guangrong
2012-08-07 9:52 ` [PATCH v5 08/12] KVM: introduce KVM_HVA_ERR_BAD Xiao Guangrong
2012-08-07 9:53 ` [PATCH v5 09/12] KVM: introduce KVM_HVA_ERR_RO_BAD Xiao Guangrong
2012-08-07 9:54 ` [PATCH v5 10/12] KVM: introduce readonly memslot Xiao Guangrong
2012-08-07 9:54 ` [PATCH v5 11/12] KVM: x86: introduce set_mmio_exit_info Xiao Guangrong
2012-08-10 18:03 ` Marcelo Tosatti
2012-08-11 3:13 ` Xiao Guangrong
2012-08-07 9:55 ` [PATCH v5 12/12] KVM: indicate readonly access fault Xiao Guangrong
2012-08-10 18:14 ` [PATCH v5 00/12] KVM: introduce readonly memslot Marcelo Tosatti
2012-08-11 3:36 ` Xiao Guangrong
2012-08-13 17:39 ` Marcelo Tosatti
2012-08-14 2:58 ` Xiao Guangrong
2012-08-14 15:25 ` Marcelo Tosatti
2012-08-16 5:49 ` Xiao Guangrong
2012-08-16 16:03 ` Marcelo Tosatti
2012-08-14 14:00 ` Avi Kivity
2012-08-14 15:51 ` Marcelo Tosatti
2012-08-15 10:44 ` Avi Kivity
2012-08-15 17:53 ` Marcelo Tosatti [this message]
2012-08-16 9:03 ` Avi Kivity
2012-08-16 15:57 ` Marcelo Tosatti
2012-08-16 16:17 ` Avi Kivity
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