other: 0.221
permissions: 0.133
semantic: 0.130
graphic: 0.096
device: 0.067
debug: 0.065
vnc: 0.053
performance: 0.050
PID: 0.039
boot: 0.039
socket: 0.031
network: 0.031
files: 0.025
KVM: 0.020
permissions: 0.405
debug: 0.118
other: 0.074
files: 0.071
device: 0.066
PID: 0.063
semantic: 0.046
boot: 0.032
vnc: 0.027
socket: 0.025
graphic: 0.024
performance: 0.021
KVM: 0.014
network: 0.014

Qemu 3.1 Aarch64 TLBI VAE1, x0

Hello,

In my code I'm trying to remove some permissions to a 4KiB MMU descriptor. After that I invalidate the MMU with 

TLBI VAE1, x0

where x0 is the start of the address of the 4 KiB page. 

In Qemu 2.12 this did not work, but I worked around it with:


    /* invalidate the address */
    TLBI VAE1, x0


    /*****************************************************************/
    /*****************************************************************/
    /* NOTE: THIS IS A TRICK FOR QEMU!!!!!!!!!!!!                                                               */
    /* Apparently we have to change the TTBR0_EL1 when we change a descriptor (especially to remove permissions) */
    /* Otherwise qemu (2.12) will continue with the same descriptor with permissions!                          **/
   /*****************************************************************/
   /*****************************************************************/
     
    /* do a trick (in qemu) */
    mrs     x1 , TTBR0_EL1

    ldr     x2 , =kernelTable0Table

    msr     TTBR0_EL1 , x2

    isb

    msr     TTBR0_EL1 , x1

    /* return from function */
    ret


That is, I just replaced the TTBR0_EL1 with a temporary value, and then restored it. (guess qemu 2.12 just needed to reload the values again).

However, even this procedure is not working with qemu 3.1. (I just tested again with qemu 2.12 and the code works fine, with qemu 3.1 it does not).

Thanks,
Pharos team

Could you provide a test binary (and the QEMU command line to run it) that demonstrates the bug, please?


Marking bug as incomplete -- we can't investigate without a test case.


[Expired for QEMU because there has been no activity for 60 days.]