Hi Philippe, Maciej, [ Maciej, a post [*] from you in 2021 is referenced in the following. ]
On 28 October 2026, Philippe Mathieu-Daudé wrote: > There is no libc for the R5900, so its tests can not run in user > mode [*]. Both Glibc and Musl are available for the R5900.[1][2] In fact, we also compile Gentoo for it. I believe the -mfix-r5900 option is used for the official Gentoo MIPS downloads.[3] As for QEMU, I maintain my own fork with R5900 user mode support since 2020, based on QEMU v5.2, as well as a corresponding Gentoo package,[4][5] because later versions of QEMU became unfixable and unusable for R5900 user mode emulation. A proper QEMU R5900 user mode must emulate the FPU like the Linux kernel does, which is why QEMU 5.2 remains the latest usable version of QEMU for the R5900. It’s worth mentioning that there are discussions on introducing additional FPU modes for the R5900 and Linux, which would allow use of FPU hardware, despite its noncompliance with IEEE 754.[6][7] > [*] > https://lore.kernel.org/qemu-devel/[email protected]/ > > Inspired-by: Maciej W. Rozycki <[email protected]> Fredrik [1] https://github.com/frno7/gentoo-mipsr5900el [2] https://github.com/frno7/gentoo-mipsr5900el/blob/d84d04b2fd9d47d5cce9c1c0884026cc37d008cf/scripts/install-crossdev#L16-L17 [3] https://www.gentoo.org/downloads/mips/ [4] https://github.com/frno7/qemu [5] https://github.com/frno7/gentoo.overlay/tree/main/app-emulation/qemu-mipsr5900el [6] https://github.com/frno7/linux/wiki/R5900-floating-point-unit-(FPU) [7] https://github.com/frno7/linux/issues/3
