>> During task switch, all of CS.DPL, CS.RPL, SS.DPL must match (in addition >> to all the other requirements) and will be the new CPL. So far this >> worked by carefully setting the CS selector and flag before doing the > > s/flag/EFLAGS/ > >> task switch; however, this will not work once we get the CPL from SS.DPL: >> setting SS itself would fail if the task switch changes the privilege >> level. > > More precisely, before patch 4 in this series setting CS.selector would > already change the CPL. After it, you actually have to set the full > segment descriptor cache to change the CPL, so we cannot use > ctxt->ops->cpl(ctxt) to retrieve the CPL during a task switch. The > check that fails without this patch is that SS.DPL must be == CPL, and > the failure happens because ctxt->ops->cpl(ctxt) is the *old* SS.DPL. This is informative and answered some of my questions. Thanks. It would be helpful to include such info in patch description. > > Paolo > >> Temporarily assume that the CPL comes from CS.RPL during task switch >> to a protected-mode task. This is the same approach used in QEMU's >> emulation code, which (until version 2.0) manually tracks the CPL. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
