[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 3/3] x86/mm-locks: apply a bias to lock levels for current domain


  • To: Jan Beulich <JBeulich@xxxxxxxx>
  • From: George Dunlap <george.dunlap@xxxxxxxxxx>
  • Date: Thu, 20 Dec 2018 14:24:54 +0000
  • Autocrypt: addr=george.dunlap@xxxxxxxxxx; prefer-encrypt=mutual; keydata= mQINBFPqG+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+zSobqlOPUO7XC5fjnwARAQABtCRHZW9yZ2UgVy4g RHVubGFwIDxkdW5sYXBnQHVtaWNoLmVkdT6JAkAEEwEKACoCGwMFCwkIBwMFFQoJCAsFFgID 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+5AQ0EVFpnOgEIAM6XPDYOTqW64Yma5+vV6947NvKfm+GvtATrwuPDX6za L2cOHhXiiM5iP7ehJCZEqgSMaG1kaQZMBsHhDbKp3dKooJrA8ODeyfV8dIfQEQ6olsV+I6+7 vcWriPgkSdawTTt1Vd9EHQAsEOC6oUf1gPiI3YcjB8I9xCRhOtTXT/4dM32i2AG7xIOO/0z0 4RbJuJvEXem1+0ZK6zoAWy/wDp2DjBIr8n2WSl9b74hHpgLy33ZNpWbe1Zul/32ym1fLT1Lm RC8zXnSb00wUt/5dRVc/TlHCw3loRhHZcalx9LGFoRPfj10wH8+ScSh/izHrcBDPA27jqAyK ZiBmSq2ftn0AEQEAAYkDRAQYAQoADwIbAgUCWmTW+QUJB+ujPwEpwF0gBBkBCgAGBQJUWmc6 AAoJELIVx6fHhBvtxesIALSpB4RaYtr2gQA9r7lTrC8bW3+aLbaBk3q7NBcfV9og6gN6Gvs8 8RITq25H+8gJNOdpKt3hQM816o6pUXTth7FYPUsNxAbo+dGoLkMhfVEYTcFpJoyXakUk/zL5 yF7CzXXI/wYMFvFoixNwdkjWJUgL1cuGh56BaLzi9hzwXjOIANV+jBuZu9xXDXWATy2YAsLB N4F5lW15eOHQ4QsfCtzX/iPjK8Q2MhdE75AsiCTjeQHntSmvi0/YwRyzSh2A8z5D6gRM4nTT HMuCROcs+KYLUUhbZs5l1OP5Srp7NFLYsqw2Zb49FG83IDmiMRsD99rGYCMxm0t1JJJ4UrzL hKgJEKY2PDEFkLRtji8P/RTPQdWZmdN29QhJ92ws/IuYmEOrwlAmvQGZWxADe+9VIoQeQaSA e/i8yuC9nbPJhl5DyrbmOv9A3EnAXvxyt1c1jpznWg3m0xuB214G7iN5l5g71tOajy9ZhId8 HKRwnmefRcT153tE0Kfw1ILgpslhUasrGuuICsMUAeNPCgdT3siIXDTD5kY/M0m7sHYdM+Ik DzK4vYhB89lZY4k87SrNEAs2YRu8nub27iRB+mb+qjSRWCVlQ1OWQ8gq2BmSoNch1zF3ukB0 KHIclPZ9EI8JpQ6qVbP6RkNPf7AdtIZrI+5eIjsVNvqhCXfaXxfB4fwHmMcbMT5f3s6CFH3M TVm/j7CpXCt8PQOZIWlDrdRhW9ywFPcKWwfUI37WAbHxJI4tzZAUytHi0TlpcQpPHXbbw10s ME4mbMuOlW/Rt01sc2d5SuZkG2/rw7E4TBq6VA3ZbSztvA6ZW6IZX/oX9dFyhw28gHG7+yRw WSNLkCgnO2rXhPJTNfOAn4bdBcQ8Adb9QbWdtqt0xpe6/NjAWGJMBmvXMiiDAKcyS3o8EXK2 CKtRdNjWisu3q/6KPQup7UxP1fMQ0dN9qGz6Cuw1tBKaTDRLS80c8i0WEHcHDSkEIx63sny1 GhyT0XIEmJfhdw99RvEh5S3CkxYnUpHay6KaHJgNKL5L2+oxzpIWA1S6uQENBFRaur0BCADt onSLWlBKZRHpldkPZgQPGJrYHJHS5mhNLs3Q1i/U6NTy/qnTXu7QVyjn5CiO799n3tJweGnn EZUCTmTFkEUNPii8l3Sch5KvdttbB83MbHXBrO193Ne3qfcwEqvsCGKgHWb6+6TfWt51R2eF u283s7jQwL5+BKTn/6NEbFjcg5U+ihArNQ7sznUag6DjCX2JrcfYTM6gaE3a+lNtPyoJwv3Z llnCQFGV2gBaftzWEQpJO5Pd/VWlKaGOdfQni68pnVXZHuuigolgUFzJILTBrxpOYC0C8uB9 yl76V6A62CoMrMu43jnHMSPKMKIjnbW3zPE0w8lj0WII82/SwKQPABEBAAGJAiUEGAEKAA8C GwwFAlpk1zMFCQfrT/YACgkQpjY8MQWQtG2/tg//YY59ZOVnER5btfVhrh+qtCoJtS0U+z55 0s/dOIoBzRJTAeWu8EY8OZHTcFN7EZtp55h3jiR/JGI9h59UIF+UqkLMrFkx1jhLHhnqF8nc fc2WZLd6ECTPvTVdVYytGzl8KoYkMhFFs+f/ZeOuxUv5OBSeQhzUbpr4S2tJdhxBLuacauOt x0GRw7eGBP/WO+Hlzp2AgeJ62MUA/xklxGb1q8hFq3g6Ghas6tUyrcx4RYEBu8hVBHqcS0VF LWLBKU+kZLNpeCwqht4VQ9FERSIk8rsScd1Qtk2uCx94cULYmiKbl6qtg+M+t4erwsdsMX2X P1kRxm6+DQJQfNZd+UP1B8jKHFbmC49JZRdK8FOAI4imealjUhHbxKS+N3072WMUIQwo0Eym 29/KJruT+JDn9R0+7PpJkCkbYiwZah8ytew+Cv9fNAA8O2t4J5q+UbpnGT9zRkkmQOoz+bza kKTbuIKqzxVjUCkHFvBwYmBYKukqC0EFm0cSQx700WCdprO6AnvO9IIeA9cBRaky3sl4lao3 XRDRjWj/GZQg8OhFPNjfAZ+S1yo0dRlqNlCtwo65B6U7d2GGb64UtjDthGBHFo8ruiwCxf5U us+iynkGfrfQHUFHCC5a8fSMal7+hrwKASyWNY4xgavv5ET61l6aGkJ+xV1hnzKlPjZGPXp8 q5c=
  • Cc: Wei Liu <wei.liu2@xxxxxxxxxx>, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>
  • Delivery-date: Thu, 20 Dec 2018 14:25:22 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
  • Openpgp: preference=signencrypt

On 12/20/18 2:01 PM, Jan Beulich wrote:
>> The practical implication of dom0 bias is that any hypercall which grabs
>> two mm locks, one of two things must be true:
>> * When it is called from one domU to another domU, locks must follow the
>> "normal" locking order listed in mm-locks.h
> 
> This would be a problem in the stubdom case.

Sure; but everything extends naturally from the 2-level case (dom0 /
domU) to the 3-level case (dom0 / stubdom / domU).

>> * When it is called between a dom0 and a domU, it must be consistenly
>> called either one way or the other; i.e., it must always be dom0 calling
>> it with a domU target, or domU calling it with a dom0 target (otherwise
>> the dom0 / domU locking order is violated).
> 
> Obviously (I hope) "domU calling it with a dom0 target" is an
> uninteresting case, because we don't allow a domU to act on
> dom0. Hence the consistency is achieved by it always going
> to be "dom0 calling it with a domU target".

We allow domU to send event channels to dom0, for instance; and
presumably Argos allows domU to send things to dom0 as well as for dom0
to send things to domU.  I don't know if those require the mm locks of
both domains, but if they did, then we'd run into a problem again.

 -George

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel

 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.