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Re: [Xen-devel] Reducing or removing direct map from xen (was Re: Ongoing/future speculative mitigation work)
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- From: Wei Liu <wei.liu2@xxxxxxxxxx>
- Date: Wed, 20 Feb 2019 17:08:09 +0000
- Cc: Martin Pohlack <mpohlack@xxxxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Joao Martins <joao.m.martins@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Daniel Kiper <daniel.kiper@xxxxxxxxxx>, Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, Anthony Liguori <aliguori@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "Dannowski, Uwe" <uwed@xxxxxxxxx>, Lars Kurth <lars.kurth@xxxxxxxxxx>, Konrad Wilk <konrad.wilk@xxxxxxxxxx>, Ross Philipson <ross.philipson@xxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>, Matt Wilson <msw@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Juergen Gross <JGross@xxxxxxxx>, Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>, "Woodhouse, David" <dwmw@xxxxxxxxxxxx>
- Delivery-date: Wed, 20 Feb 2019 17:08:16 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Wed, Feb 20, 2019 at 01:09:56PM +0000, Wei Liu wrote:
[...]
> I think under-allocate-then-map looks plausible. xmalloc will need
> to allocate pages, put them into an array and call __vmap on that array
> directly.
The biggest issue with this approach is that we now need an array of
1UL<<MAX_ORDER to accommodate mfns. Back of envelope calculation: on x86
this is going to be (1UL<<20)*8 bytes long. This is not feasible.
Wei.
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