kernel/arch/powerpc/platforms/microwatt, branch linux-6.2.y

random: remove CONFIG_ARCH_RANDOM

2022-07-18T13:03:37Z

When RDRAND was introduced, there was much discussion on whether it should be trusted and how the kernel should handle that. Initially, two mechanisms cropped up, CONFIG_ARCH_RANDOM, a compile time switch, and "nordrand", a boot-time switch. Later the thinking evolved. With a properly designed RNG, using RDRAND values alone won't harm anything, even if the outputs are malicious. Rather, the issue is whether those values are being *trusted* to be good or not. And so a new set of options were introduced as the real ones that people use -- CONFIG_RANDOM_TRUST_CPU and "random.trust_cpu". With these options, RDRAND is used, but it's not always credited. So in the worst case, it does nothing, and in the best case, maybe it helps. Along the way, CONFIG_ARCH_RANDOM's meaning got sort of pulled into the center and became something certain platforms force-select. The old options don't really help with much, and it's a bit odd to have special handling for these instructions when the kernel can deal fine with the existence or untrusted existence or broken existence or non-existence of that CPU capability. Simplify the situation by removing CONFIG_ARCH_RANDOM and using the ordinary asm-generic fallback pattern instead, keeping the two options that are actually used. For now it leaves "nordrand" for now, as the removal of that will take a different route. Acked-by: Michael Ellerman Acked-by: Catalin Marinas Acked-by: Borislav Petkov Acked-by: Heiko Carstens Acked-by: Greg Kroah-Hartman Signed-off-by: Jason A. Donenfeld

powerpc/microwatt: wire up rng during setup_arch()

2022-06-18T00:19:10Z

The platform's RNG must be available before random_init() in order to be useful for initial seeding, which in turn means that it needs to be called from setup_arch(), rather than from an init call. Fortunately, each platform already has a setup_arch function pointer, which means it's easy to wire this up. This commit also removes some noisy log messages that don't add much. Fixes: c25769fddaec ("powerpc/microwatt: Add support for hardware random number generator") Cc: stable@vger.kernel.org # v5.14+ Signed-off-by: Jason A. Donenfeld Reviewed-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220611151015.548325-2-Jason@zx2c4.com

powerpc/microwatt: add POWER9_CPU, clear PPC_64S_HASH_MMU

2021-12-09T11:41:16Z

Microwatt implements a subset of ISA v3.0 (which is equivalent to the POWER9_CPU option). It is radix-only, so does not require hash MMU support. This saves 20kB compressed dtbImage and 56kB vmlinux size. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211201144153.2456614-19-npiggin@gmail.com

powerpc/64s: Make hash MMU support configurable

2021-12-09T11:40:24Z

This adds Kconfig selection which allows 64s hash MMU support to be disabled. It can be disabled if radix support is enabled, the minimum supported CPU type is POWER9 (or higher), and KVM is not selected. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211201144153.2456614-17-npiggin@gmail.com

powerpc: Rename PPC_NATIVE to PPC_HASH_MMU_NATIVE

2021-12-02T11:57:22Z

PPC_NATIVE now only controls the native HPT code, so rename it to be more descriptive. Restrict it to Book3S only. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211201144153.2456614-3-npiggin@gmail.com

powerpc/microwatt: Make microwatt_get_random_darn() static

2021-11-25T00:25:34Z

Make microwatt_get_random_darn() static, because it can be. Reported-by: kernel test robot Signed-off-by: Michael Ellerman Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211118004415.1706863-1-mpe@ellerman.id.au

powerpc/microwatt: Add support for hardware random number generator

2021-06-21T11:16:32Z

Microwatt's hardware RNG is accessed using the DARN instruction. Signed-off-by: Paul Mackerras Reviewed-by: Nicholas Piggin Reviewed-by: Segher Boessenkool Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/YMwXPHlV/ZleiQUY@thinks.paulus.ozlabs.org

powerpc/microwatt: Use standard 16550 UART for console

2021-06-21T11:16:31Z

This adds support to the Microwatt platform to use the standard 16550-style UART which available in the standalone Microwatt FPGA. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras Reviewed-by: Segher Boessenkool Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/YMwXGCTzedpQje7r@thinks.paulus.ozlabs.org

powerpc/xics: Add a native ICS backend for microwatt

2021-06-21T11:15:58Z

This is a simple native ICS backend that matches the layout of the Microwatt implementation of ICS. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras Reviewed-by: Segher Boessenkool [mpe: Add empty ics_native_init() to unbreak non-microwatt builds] Signed-off-by: Michael Ellerman fixup-ics Link: https://lore.kernel.org/r/YMwW8cxrwB2W5EUN@thinks.paulus.ozlabs.org

powerpc/microwatt: Populate platform bus from device-tree

2021-06-21T11:15:26Z

Just like any other embedded platform. Add an empty soc node. Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras Reviewed-by: Segher Boessenkool Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/YMwWx98+PMibZq/G@thinks.paulus.ozlabs.org