Am 24.01.2012 15:16, schrieb Gleb Natapov: > On Tue, Jan 24, 2012 at 03:15:13PM +0100, Kevin Wolf wrote: >> Am 24.01.2012 15:03, schrieb Joerg Roedel: >>> On Mon, Jan 23, 2012 at 05:10:46PM +0100, Kevin Wolf wrote: >>>> This patch fixes the problem for VMX. For SVM, the logic used to >>>> determine the source of the task switch is buggy, so we can't pass >>>> useful information to the emulator there and just disable the check in >>>> all cases. >>> >>> Actually, SVM isn't buggy :) For SVM you do not need to do any >>> priviledge checks in software because the hardware already takes care of >>> that. >>> In other words, KVM only gets a task-switch intercept if the priviledges >>> are all checked and correct. >> >> Okay, that's good to hear. The current code is still buggy because as >> Gleb noted it checks against the TSS DPL. We need to disable that check >> for SVM then. Also all checks for TASK_SWITCH_GATE indicate that >> something is wrong because it will never happen. >> > Not necessary. Currently all checks for TASK_SWITCH_GATE also check for > TASK_SWITCH_CALL, so I think you can fix SVM case in your patch by > passing TASK_SWITCH_GATE instead of TASK_SWITCH_CALL to > kvm_task_switch(). Yes, the emulator itself would be fixed by passing TASK_SWITCH_GATE and idt_index = -1 (although it looks a bit brittle). However, task_switch_interception() itself does some more based on the value of reason, for example it decides whether or not to call skip_emulated_instruction(). Kevin -- 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
