On Fri, 17 Oct 2025 17:19:18 +0100, Maximilian Dittgen mdittgen@amazon.de wrote:
When mapping guest ITS collections, vgic_lpi_stress iterates over integers in the range [0, nr_cpus), passing them as the target_addr parameter to its_send_mapc_cmd(). These integers correspond to the selftest userspace vCPU IDs that we intend to map each ITS collection to.
However, its_encode_target() within its_send_mapc_cmd() expects a vCPU's redistributor address--not the vCPU ID--as the target_addr parameter. This is evident from how its_encode_target() encodes the target_addr parameter as:
its_mask_encode(&cmd->raw_cmd[2], target_addr >> 16, 51, 16)This shows that we right-shift the input target_addr parameter by 16 bits before encoding it. This makes sense when the parameter refers to redistributor addresses (e.g., 0x20000, 0x30000) but not vCPU IDs (e.g., 0x2, 0x3).
From the KVM ITS emulation code:
* We use linear CPU numbers for redistributor addressing, * so GITS_TYPER.PTA is 0.
It is not an address.
M.