On Sat, Feb 03, 2024, Mathias Krause wrote: > The ioctl()s to get and set KVM's debug registers are broken for 32 bit > kernels as they'd only copy half of the user register state because of a > UAPI and in-kernel type mismatch (__u64 vs. unsigned long; 8 vs. 4 > bytes). > > This makes it impossible for userland to set anything but DR0 without > resorting to bit folding tricks. > > Switch to a loop for copying debug registers that'll implicitly do the > type conversion for us, if needed. > > There are likely no users (left) for 32bit KVM, fix the bug nonetheless. And this has always been broken, so if there were ever users of 32-bit KVM, they obviously didn't use this API :-) If the code weren't also a cleanup for 64-bit, I would vote to change the APIs to just fail for 32-bit. But there's just no good reason to assume that the layouts of KVM's internal storage and "struct kvm_debugregs" are identical.
