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Diffstat (limited to 'gitlab/issues_text/target_arm/host_missing/accel_TCG/2250')
| -rw-r--r-- | gitlab/issues_text/target_arm/host_missing/accel_TCG/2250 | 44 |
1 files changed, 0 insertions, 44 deletions
diff --git a/gitlab/issues_text/target_arm/host_missing/accel_TCG/2250 b/gitlab/issues_text/target_arm/host_missing/accel_TCG/2250 deleted file mode 100644 index 9e9a9051a..000000000 --- a/gitlab/issues_text/target_arm/host_missing/accel_TCG/2250 +++ /dev/null @@ -1,44 +0,0 @@ -FEAT_RME: NS EL1/0 Address Translation from EL3 fails -Description of problem: -I'm playing around with the QEMU RME Stack (TF-A, TF-RMM, Linux/KVM) for a research project. -For this I want to access some virtual normal world memory address from within EL3. -To translate the address to the physical address I use the `AT` instructions (e.g., `ats1e2r`). -If the NW memory is initially mapped in the GPT as `GPT_GPI_ANY`, this works fine, however, if the NW memory is mapped as `GPT_GPI_NS` the address translation fails with the error `0b100101`/GPT on PTW. -However, EL3/Root World should be able to access memory from all PAS, and therefore, if I understand the ARM documentation correctly, should also be able to execute a PTW for an address marked NS in the GPT. -Steps to reproduce: -1. Setup GPT with some memory marked as `GPT_GPI_NS` -2. Forward some NW virtual address from the kernel to EL3 -3. Execute a PTW on this address via the `AT` instructions. -Additional information: -I also took a look into the QEMU source code and potentially found the issue. -When executing a PTW we execute `target/arm/ptw.c:granule_protection_check`. -The function extracts the target page's GPI (`ptw.c:440'): -```c - switch (gpi) { - case 0b0000: /* no access */ - break; - case 0b1111: /* all access */ - return true; - case 0b1000: - case 0b1001: - case 0b1010: - case 0b1011: - if (pspace == (gpi & 3)) { - return true; - } - break; - default: - goto fault_walk; /* reserved */ - } -``` -The if statement checks if the current `pstate` (previously set to `ptw->in_space`) is the same security state as the one contained in the GPI. -If this is not the case, we generate a GPF. -However, I think the code misses the fact, that EL3/Root world can access memory from each PAS, meaning that the if statement should be something like -```c -if (pspace == (gpi & 3) || (pspace == ARMSS_Root)) { - return true; -} -``` -Additionally, as both Secure and Realm World can also access Normal World memory, similar checks should also be added in such cases. - -I have a patch prepared for this, however, I first want to check in if I'm in line with the Arm ARM or if I'm missing something and EL3 is indeed not supposed to execute PTWs for NS memory. |