Date: Mon, 26 Aug 2013 13:37:57 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-virtualization@freebsd.org Subject: Re: CFT: nested page table integration with amd64/pmap Message-ID: <kvfemd$9i6$1@ger.gmane.org> In-Reply-To: <5217DAB2.3020204@freebsd.org> References: <CAFgRE9H2n63%2B3GFwWNwE-Zu3gHPBcWhD4g6frB_ksXz=HAXp5w@mail.gmail.com> <kv7dig$id5$1@ger.gmane.org> <5217DAB2.3020204@freebsd.org>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) ------enig2NLPFFCTIKSWKSOWPVILW Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 23/08/2013 23:57, Peter Grehan wrote: >> I always wondered about virtualization environments which have pageabl= e >> guest memory - how does the guest kernel handle situations where it >> really needs non-pageable memory? Does is simply "not care" because fo= r >> it the memory access looks just like it isn't paged but is simply very= , >> very slow? >=20 > Yes - from the guest's point of view, what it thinks is physical memor= y > appears wired. >=20 >> What about time-sensitive situations (like the originally >> mentioned PCI-passthrough)? >=20 > PCI passthru is a special case since the h/w requires that the target > of a DMA transfer is present - there is currently no way for the IOMMU > to generate the equivalent of page faults. So, for PCI passthru, all of= > guest memory has to be wired host memory. >=20 > For time-sensitive situations, there's not a lot of options other than= > forcing guest memory to be wired, since there isn't visibility into the= > host without having o/s-specific "tools" that could communicate this > information to the hypervisor. Ok, that is how I understood it also, but I thought that maybe there was some way of telling which guest memory belongs to the kernel and only wire those pages. ------enig2NLPFFCTIKSWKSOWPVILW Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (FreeBSD) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iEYEARECAAYFAlIbPhUACgkQ/QjVBj3/HSzWjwCfcnzArU4Z2B5YSuliqK9/H4Ji GucAoJyfhU5Izyns6FiJDZWuRG66Ki0h =MtW9 -----END PGP SIGNATURE----- ------enig2NLPFFCTIKSWKSOWPVILW--
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