Re: [PATCH 11/12] riscv: don't use global static vars to store alternative data

Christoph Hellwig
2022-05-16T06:16:15Z

On Wed, May 11, 2022 at 09:29:20PM +0200, Heiko Stuebner wrote:
> Right now the code uses a global struct to store vendor-ids
> and another global variable to store the vendor-patch-function.
>
> There exist specific cases where we'll need to patch the kernel
> at an even earlier stage, where trying to write to a static
> variable might actually result in hangs.
>
> Also collecting the vendor-information consists of 3 sbi-ecalls
> (or csr-reads) which is pretty negligible in the context of
> booting a kernel.
>
> So rework the code to not rely on static variables and instead
> collect the vendor-information when a round of alternatives is
> to be applied.
>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> Reviewed-by: Guo Ren <guoren@kernel.org>
> Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
> ---
> arch/riscv/kernel/alternative.c | 51 ++++++++++++++++-----------------
> 1 file changed, 24 insertions(+), 27 deletions(-)
>
> diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
> index e6c9de9f9ba6..27f722ae452b 100644
> --- a/arch/riscv/kernel/alternative.c
> +++ b/arch/riscv/kernel/alternative.c
> @@ -16,41 +16,35 @@
> #include <asm/sbi.h>
> #include <asm/csr.h>
>
> -static struct cpu_manufacturer_info_t {
> +struct cpu_manufacturer_info_t {
> unsigned long vendor_id;
> unsigned long arch_id;
> unsigned long imp_id;
> -} cpu_mfr_info;
> + void (*vendor_patch_func)(struct alt_entry *begin, struct alt_entry *end,
> + unsigned long archid, unsigned long impid,
> + unsigned int stage);

Please drop the confusing vendor_ prefix for the function pointer
while you're at it. The vendor id is just one of three inputs for
the patching.

Otherwise this looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>