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Re: [Xen-devel] Ongoing/future speculative mitigation work
- To: Jan Beulich <JBeulich@xxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>
- From: George Dunlap <george.dunlap@xxxxxxxxxx>
- Date: Thu, 25 Oct 2018 15:56:50 +0100
- Autocrypt: addr=george.dunlap@xxxxxxxxxx; prefer-encrypt=mutual; keydata= xsFNBFPqG+MBEACwPYTQpHepyshcufo0dVmqxDo917iWPslB8lauFxVf4WZtGvQSsKStHJSj 92Qkxp4CH2DwudI8qpVbnWCXsZxodDWac9c3PordLwz5/XL41LevEoM3NWRm5TNgJ3ckPA+J K5OfSK04QtmwSHFP3G/SXDJpGs+oDJgASta2AOl9vPV+t3xG6xyfa2NMGn9wmEvvVMD44Z7R W3RhZPn/NEZ5gaJhIUMgTChGwwWDOX0YPY19vcy5fT4bTIxvoZsLOkLSGoZb/jHIzkAAznug Q7PPeZJ1kXpbW9EHHaUHiCD9C87dMyty0N3TmWfp0VvBCaw32yFtM9jUgB7UVneoZUMUKeHA fgIXhJ7I7JFmw3J0PjGLxCLHf2Q5JOD8jeEXpdxugqF7B/fWYYmyIgwKutiGZeoPhl9c/7RE Bf6f9Qv4AtQoJwtLw6+5pDXsTD5q/GwhPjt7ohF7aQZTMMHhZuS52/izKhDzIufl6uiqUBge 0lqG+/ViLKwCkxHDREuSUTtfjRc9/AoAt2V2HOfgKORSCjFC1eI0+8UMxlfdq2z1AAchinU0 eSkRpX2An3CPEjgGFmu2Je4a/R/Kd6nGU8AFaE8ta0oq5BSFDRYdcKchw4TSxetkG6iUtqOO ZFS7VAdF00eqFJNQpi6IUQryhnrOByw+zSobqlOPUO7XC5fjnwARAQABzSRHZW9yZ2UgVy4g RHVubGFwIDxkdW5sYXBnQHVtaWNoLmVkdT7CwYAEEwEKACoCGwMFCwkIBwMFFQoJCAsFFgID AQACHgECF4ACGQEFAlpk2IEFCQo9I54ACgkQpjY8MQWQtG1A1BAAnc0oX3+M/jyv4j/ESJTO U2JhuWUWV6NFuzU10pUmMqpgQtiVEVU2QbCvTcZS1U/S6bqAUoiWQreDMSSgGH3a3BmRNi8n HKtarJqyK81aERM2HrjYkC1ZlRYG+jS8oWzzQrCQiTwn3eFLJrHjqowTbwahoiMw/nJ+OrZO /VXLfNeaxA5GF6emwgbpshwaUtESQ/MC5hFAFmUBZKAxp9CXG2ZhTP6ROV4fwhpnHaz8z+BT NQz8YwA4gkmFJbDUA9I0Cm9D/EZscrCGMeaVvcyldbMhWS+aH8nbqv6brhgbJEQS22eKCZDD J/ng5ea25QnS0fqu3bMrH39tDqeh7rVnt8Yu/YgOwc3XmgzmAhIDyzSinYEWJ1FkOVpIbGl9 uR6seRsfJmUK84KCScjkBhMKTOixWgNEQ/zTcLUsfTh6KQdLTn083Q5aFxWOIal2hiy9UyqR VQydowXy4Xx58rqvZjuYzdGDdAUlZ+D2O3Jp28ez5SikA/ZaaoGI9S1VWvQsQdzNfD2D+xfL qfd9yv7gko9eTJzv5zFr2MedtRb/nCrMTnvLkwNX4abB5+19JGneeRU4jy7yDYAhUXcI/waS /hHioT9MOjMh+DoLCgeZJYaOcgQdORY/IclLiLq4yFnG+4Ocft8igp79dbYYHkAkmC9te/2x Kq9nEd0Hg288EO/OwE0EVFq6vQEIAO2idItaUEplEemV2Q9mBA8YmtgckdLmaE0uzdDWL9To 1PL+qdNe7tBXKOfkKI7v32fe0nB4aecRlQJOZMWQRQ0+KLyXdJyHkq9221sHzcxsdcGs7X3c 17ep9zASq+wIYqAdZvr7pN9a3nVHZ4W7bzezuNDAvn4EpOf/o0RsWNyDlT6KECs1DuzOdRqD oOMJfYmtx9hMzqBoTdr6U20/KgnC/dmWWcJAUZXaAFp+3NYRCkk7k939VaUpoY519CeLrymd Vdke66KCiWBQXMkgtMGvGk5gLQLy4H3KXvpXoDrYKgysy7jeOccxI8owoiOdtbfM8TTDyWPR Ygjzb9LApA8AEQEAAcLBZQQYAQoADwIbDAUCWmTXMwUJB+tP9gAKCRCmNjwxBZC0bb+2D/9h jn1k5WcRHlu19WGuH6q0Kgm1LRT7PnnSz904igHNElMB5a7wRjw5kdNwU3sRm2nnmHeOJH8k Yj2Hn1QgX5SqQsysWTHWOEseGeoXydx9zZZkt3oQJM+9NV1VjK0bOXwqhiQyEUWz5/9l467F S/k4FJ5CHNRumvhLa0l2HEEu5pxq463HQZHDt4YE/9Y74eXOnYCB4nrYxQD/GSXEZvWryEWr eDoaFqzq1TKtzHhFgQG7yFUEepxLRUUtYsEpT6Rks2l4LCqG3hVD0URFIiTyuxJx3VC2Ta4L H3hxQtiaIpuXqq2D4z63h6vCx2wxfZc/WRHGbr4NAlB81l35Q/UHyMocVuYLj0llF0rwU4Aj iKZ5qWNSEdvEpL43fTvZYxQhDCjQTKbb38omu5P4kOf1HT7s+kmQKRtiLBlqHzK17D4K/180 ADw7a3gnmr5RumcZP3NGSSZA6jP5vNqQpNu4gqrPFWNQKQcW8HBiYFgq6SoLQQWbRxJDHvTR YJ2ms7oCe870gh4D1wFFqTLeyXiVqjddENGNaP8ZlCDw6EU82N8Bn5LXKjR1GWo2UK3CjrkH pTt3YYZvrhS2MO2EYEcWjyu6LALF/lS6z6LKeQZ+t9AdQUcILlrx9IxqXv6GvAoBLJY1jjGB q+/kRPrWXpoaQn7FXWGfMqU+NkY9enyrlw==
- Cc: Martin Pohlack <mpohlack@xxxxxxxxx>, Julien Grall <julien.grall@xxxxxxx>, Joao Martins <joao.m.martins@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Mihai Dontu <mdontu@xxxxxxxxxxxxxxx>, Marek Marczykowski <marmarek@xxxxxxxxxxxxxxxxxxxxxx>, Anthony Liguori <aliguori@xxxxxxxxxx>, uwed@xxxxxxxxx, Lars Kurth <lars.kurth@xxxxxxxxxx>, Konrad Rzeszutek 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>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel List <xen-devel@xxxxxxxxxxxxx>, Daniel Kiper <daniel.kiper@xxxxxxxxxx>, David Woodhouse <dwmw@xxxxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
- Delivery-date: Thu, 25 Oct 2018 14:56:59 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 10/25/2018 03:50 PM, Jan Beulich wrote:
>>>> On 22.10.18 at 16:55, <wei.liu2@xxxxxxxxxx> wrote:
>> On Thu, Oct 18, 2018 at 06:46:22PM +0100, Andrew Cooper wrote:
>>> An easy first step here is to remove Xen's directmap, which will mean
>>> that guests general RAM isn't mapped by default into Xen's address
>>> space. This will come with some performance hit, as the
>>> map_domain_page() infrastructure will now have to actually
>>> create/destroy mappings, but removing the directmap will cause an
>>> improvement for non-speculative security as well (No possibility of
>>> ret2dir as an exploit technique).
>>
>> I have looked into making the "separate xenheap domheap with partial
>> direct map" mode (see common/page_alloc.c) work but found it not as
>> straight forward as it should've been.
>>
>> Before I spend more time on this, I would like some opinions on if there
>> is other approach which might be more useful than that mode.
>
> How would such a split heap model help with L1TF, where the
> guest specifies host physical addresses in its vulnerable page
> table entries
I don't think it would.
> (and hence could spy at xenheap but - due to not
> being mapped - not domheap)?
Er, didn't follow this bit -- if L1TF is related to host physical
addresses, how does having a virtual mapping in Xen affect things in any
way?
-George
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