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<think>
Alright, I'm trying to figure out whether this QEMU issue is related to user-mode or system-mode. Let me start by understanding the problem.
The user reported that when they run a specific test program using QEMU-user, it doesn't report HWCAP2_MTE. They provided two scenarios: one where the program works and prints "OK", and another where it fails, printing "0".
Looking at the first case, they used clang to compile with `-fsanitize=memtag` and `-march=armv8+memtag`, then ran the binary under QEMU-aarch64 with `--cpu max`. The program worked as expected. This suggests that when MTE is enabled in the CPU, QEMU correctly reports it.
In the second case, they wrote a small C program to check if HWCAP2_MTE is set using `getauxval(AT_HWCAP2)`. They compiled and ran it similarly but got "0", meaning the bit wasn't set. This implies that even though MTE was enabled in the CPU configuration, QEMU didn't communicate this correctly to the program.
Now, considering QEMU has two main modes: user-mode and system-mode. User-mode runs individual applications without a full OS, while system-mode emulates an entire machine with peripherals, devices, and higher privileges.
In this case, since the issue is about how auxiliary values (like HWCAP2) are being reported to the application running under QEMU, it's likely related to user-mode. User-mode handles setting up the environment for individual processes, including passing necessary information through auxv vectors. The fact that the CPU features aren't correctly reflected in AT_HWCAP2 points to a problem in how QEMU-user sets these values.
I don't see any mention of system-level components like devices or higher privileges here. It's purely about the application reading CPU capabilities, which falls under user-mode responsibilities.
</think>
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