MMU privileges

By: sr (nobody.delete@this.nowhere.com), September 21, 2021 10:07 am
Room: Moderated Discussions
Linus Torvalds (torvalds.delete@this.linux-foundation.org) on September 21, 2021 10:04 am wrote:

> And it doesn't even fix the permission problems. We considered using segmentation to fix Meltdown,
> but even the segment range check wasn't necessarily done early enough, so while it helped the
> data leak in some situations, it had the same fundamental issues that a TLB lookup did.

By description MMU first check privilege level and only after success gives access to data. No matter which kind of privilege checking system is used if MMU fist gives data and checks permissions later, that data can be leaked through side-channels.

It's a fundamental problem that Meltdown cpus did wrong.
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TopicPosted ByDate
POWER10 SAP SD benchmarkanon22021/09/06 02:36 PM
  POWER10 SAP SD benchmarkDaniel B2021/09/07 01:31 AM
    "Cores" (and SPEC)Rayla2021/09/07 06:51 AM
      "Cores" (and SPEC)anon2021/09/07 02:56 PM
  POWER10 SAP SD benchmarkAnon2021/09/07 02:24 PM
    POWER10 SAP SD benchmarkAnon2021/09/07 02:27 PM
  Virtually tagged L1-cachessr2021/09/08 04:49 AM
    Virtually tagged L1-cachesdmcq2021/09/08 07:22 AM
      Virtually tagged L1-cachessr2021/09/08 07:56 AM
      Virtually tagged L1-cachesHugo Décharnes2021/09/08 07:58 AM
        Virtually tagged L1-cachessr2021/09/08 09:09 AM
          Virtually tagged L1-cachesHugo Décharnes2021/09/08 09:46 AM
            Virtually tagged L1-cachessr2021/09/08 10:35 AM
              Virtually tagged L1-cachesHugo Décharnes2021/09/08 11:23 AM
                Virtually tagged L1-cachessr2021/09/08 11:40 AM
                  Virtually tagged L1-cachesanon2021/09/09 02:16 AM
                    Virtually tagged L1-cachesKonrad Schwarz2021/09/10 04:19 AM
                      Virtually tagged L1-cachesHugo Décharnes2021/09/10 05:59 AM
                        Virtually tagged L1-cachesanon2021/09/14 02:17 AM
                          Virtually tagged L1-cachesdmcq2021/09/14 08:34 AM
                            Or use a PLB (NT)Paul A. Clayton2021/09/14 08:45 AM
                              Or use a PLBLinus Torvalds2021/09/14 02:27 PM
                                Or use a PLBanon2021/09/14 11:15 PM
                                  Or use a PLBMichael S2021/09/15 02:21 AM
                                    Or use a PLBdmcq2021/09/15 02:42 PM
                                      Or use a PLBKonrad Schwarz2021/09/16 03:24 AM
                                        Or use a PLBMichael S2021/09/16 09:13 AM
                                          Or use a PLB---2021/09/16 12:02 PM
                                  PLB referencePaul A. Clayton2021/09/18 01:35 PM
                                    PLB referenceMichael S2021/09/18 03:14 PM
                                      Demand paging/translation orthogonalPaul A. Clayton2021/09/19 06:33 AM
                                        Demand paging/translation orthogonalMichael S2021/09/19 08:10 AM
                                      PLB referenceCarson2021/09/20 09:19 PM
                                    PLB referencesr2021/09/20 05:02 AM
                                      PLB referenceMichael S2021/09/20 06:03 AM
                                        PLB referenceLinus Torvalds2021/09/20 11:10 AM
                                  Or use a PLBsr2021/09/20 03:32 AM
                              Or use a PLBsr2021/09/21 08:36 AM
                                Or use a PLBLinus Torvalds2021/09/21 09:04 AM
                                  Or use a PLBsr2021/09/21 09:48 AM
                                    Or use a PLBLinus Torvalds2021/09/21 12:55 PM
                                      Or use a PLBsr2021/09/22 05:55 AM
                                        Or use a PLBrwessel2021/09/22 06:09 AM
                                        Or use a PLBLinus Torvalds2021/09/22 10:50 AM
                                          Or use a PLBsr2021/09/22 12:00 PM
                                            Or use a PLBdmcq2021/09/22 03:07 PM
                                            Or use a PLBEtienne Lorrain2021/09/23 07:50 AM
                                          Or use a PLBanon22021/09/22 03:09 PM
                                            Or use a PLBdmcq2021/09/23 01:35 AM
                                          Or use a PLB2021/09/23 08:37 AM
                                            Or use a PLBLinus Torvalds2021/09/23 11:01 AM
                                              Or use a PLBgpd2021/09/24 02:59 AM
                                                Or use a PLBLinus Torvalds2021/09/24 09:45 AM
                                                  Or use a PLBdmcq2021/09/24 11:43 AM
                                                  Or use a PLBsr2021/09/25 09:19 AM
                                                    Or use a PLBLinus Torvalds2021/09/25 09:44 AM
                                                      Or use a PLBsr2021/09/25 10:11 AM
                                                        Or use a PLBLinus Torvalds2021/09/25 10:31 AM
                                                          Or use a PLBsr2021/09/25 10:52 AM
                                                            Or use a PLBLinus Torvalds2021/09/25 11:05 AM
                                                              Or use a PLBsr2021/09/25 11:23 AM
                                                                Or use a PLBrwessel2021/09/25 02:29 PM
                                                                  Or use a PLBsr2021/09/30 11:22 PM
                                                                    Or use a PLBrwessel2021/10/01 05:19 AM
                                                                      Or use a PLBDavid Hess2021/10/01 09:35 AM
                                                                        Or use a PLBrwessel2021/10/02 03:47 AM
                                                                      Or use a PLBsr2021/10/02 10:16 AM
                                                                        Or use a PLBrwessel2021/10/02 10:53 AM
                                                          Or use a PLBLinus Torvalds2021/09/25 10:57 AM
                                                            Or use a PLBsr2021/09/25 11:07 AM
                                                              Or use a PLBLinus Torvalds2021/09/25 11:21 AM
                                                                Or use a PLBsr2021/09/25 11:40 AM
                                                                  Or use a PLBnksingh2021/09/27 08:07 AM
                                                          Or use a PLB2021/09/27 08:02 AM
                                                            Or use a PLBLinus Torvalds2021/09/27 09:20 AM
                                                              Or use a PLBLinus Torvalds2021/09/27 11:58 AM
                                                                Or use a PLBdmcq2021/09/28 09:59 AM
                                              Or use a PLBsr2021/09/25 09:34 AM
                                                Or use a PLBrwessel2021/09/25 02:44 PM
                                                  Or use a PLBsr2021/10/01 12:04 AM
                                                    Or use a PLBrwessel2021/10/01 05:33 AM
                                                      I386 segmentation highlightssr2021/10/04 06:53 AM
                                                        I386 segmentation highlightsAdrian2021/10/04 08:53 AM
                                                          I386 segmentation highlightssr2021/10/04 09:19 AM
                                                        I386 segmentation highlightsrwessel2021/10/04 03:57 PM
                                                          I386 segmentation highlightssr2021/10/05 10:16 AM
                                                            I386 segmentation highlightsMichael S2021/10/05 11:27 AM
                                                            I386 segmentation highlightsrwessel2021/10/05 03:20 PM
                                                Or use a PLBJohnG2021/09/25 09:18 PM
                                              Or use a PLB2021/09/27 06:37 AM
                                                Or use a PLBHeikki Kultala2021/09/28 02:53 AM
                                                  Or use a PLBrwessel2021/09/28 06:29 AM
                                        Or use a PLBDavid Hess2021/09/23 05:00 PM
                                          Or use a PLBAdrian2021/09/24 12:21 AM
                                            Or use a PLBdmcq2021/09/25 11:41 AM
                                        Or use a PLBblaine2021/09/26 10:19 PM
                                          Or use a PLBDavid Hess2021/09/27 10:35 AM
                                            Or use a PLBblaine2021/09/27 04:19 PM
                                            Or use a PLBAdrian2021/09/27 09:40 PM
                                              Or use a PLBAdrian2021/09/27 09:59 PM
                                                Or use a PLBdmcq2021/09/28 06:45 AM
                                              Or use a PLBrwessel2021/09/28 06:45 AM
                                              Or use a PLBDavid Hess2021/09/28 11:50 AM
                                                Or use a PLBEtienne Lorrain2021/09/30 12:25 AM
                                                  Or use a PLBDavid Hess2021/10/01 09:40 AM
                                  MMU privilegessr2021/09/21 10:07 AM
                                    MMU privilegesLinus Torvalds2021/09/21 12:49 PM
                            Virtually tagged L1-cachesKonrad Schwarz2021/09/16 03:18 AM
                          Virtually tagged L1-cachesCarson2021/09/16 12:12 PM
                            Virtually tagged L1-cachesanon22021/09/16 04:16 PM
                              Virtually tagged L1-cachesrwessel2021/09/16 05:29 PM
                          Virtually tagged L1-cachessr2021/09/20 03:20 AM
              Virtually tagged L1-caches---2021/09/08 01:28 PM
                Virtually tagged L1-cachesanonymou52021/09/08 07:28 PM
                  Virtually tagged L1-cachesanonymou52021/09/08 07:34 PM
                  Virtually tagged L1-caches---2021/09/09 09:14 AM
                    Virtually tagged L1-cachesanonymou52021/09/09 09:44 PM
                Multi-threading?David Kanter2021/09/09 08:32 PM
                  Multi-threading?---2021/09/10 08:19 AM
                Virtually tagged L1-cachessr2021/09/11 12:19 AM
                Virtually tagged L1-cachessr2021/09/11 12:36 AM
                  Virtually tagged L1-caches---2021/09/11 08:53 AM
                    Virtually tagged L1-cachessr2021/09/11 11:43 PM
                      Virtually tagged L1-cachesLinus Torvalds2021/09/12 10:10 AM
                        Virtually tagged L1-cachessr2021/09/12 10:57 AM
                          Virtually tagged L1-cachesdmcq2021/09/13 07:31 AM
                            Virtually tagged L1-cachessr2021/09/20 03:11 AM
            Virtually tagged L1-cachessr2021/09/11 01:49 AM
      Virtually tagged L1-cachesLinus Torvalds2021/09/08 11:34 AM
        Virtually tagged L1-cachesdmcq2021/09/09 01:46 AM
          Virtually tagged L1-cachesdmcq2021/09/09 01:58 AM
          Virtually tagged L1-cachessr2021/09/11 12:29 AM
            Virtually tagged L1-cachesdmcq2021/09/11 07:59 AM
              Virtually tagged L1-cachessr2021/09/11 11:57 PM
                Virtually tagged L1-cachesdmcq2021/09/12 07:44 AM
                  Virtually tagged L1-cachessr2021/09/12 08:48 AM
                    Virtually tagged L1-cachesdmcq2021/09/12 12:22 PM
                      Virtually tagged L1-cachessr2021/09/20 03:40 AM
    Where do you see this information? (NT)anon22021/09/09 01:45 AM
      Where do you see this information?sr2021/09/11 12:40 AM
        Where do you see this information?anon22021/09/11 12:53 AM
          Where do you see this information?sr2021/09/11 01:08 AM
            Thank you (NT)anon22021/09/11 03:31 PM
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