Re: [Minios-devel] [UNIKRAFT RFC PATCH 5/5] plat/arm: Support fp/simd save/restore during context switch

[Julien Grall <julien@xxxxxxx>]

On 19/12/2019 14:27, Jia He wrote:
> Floating point feature is useful for some applications. We should
> save/restore fp registers during context switch.
>
> Signed-off-by: Jia He <justin.he@xxxxxxx>
> ---
>   plat/common/arm/thread_start64.S    | 83 +++++++++++++++++++++++++++++
>   plat/common/include/arm/arm64/cpu.h | 46 +++++++++++++++-
>   2 files changed, 127 insertions(+), 2 deletions(-)
>
> diff --git a/plat/common/arm/thread_start64.S b/plat/common/arm/thread_start64.S
> index 9a80f62..d810704 100644
> --- a/plat/common/arm/thread_start64.S
> +++ b/plat/common/arm/thread_start64.S
> @@ -34,6 +34,7 @@
>   #include <uk/plat/common/sw_ctx.h>
>   #include <uk/arch/lcpu.h>
>   #include <uk/asm.h>
> +#include <uk/config.h>
>   
>   /*
>    * Thread stack memory layout:
> @@ -121,3 +122,85 @@ restore_point:
>         add sp, x2, #__CALLEE_SAVED_SIZE
>         ret
>   ENDPROC(asm_sw_ctx_switch)
> +
> +#ifdef CONFIG_FLOAT_POINT
> +.macro fpsimd_save state, tmpnr
> +       stp     q0, q1, [\state, #16 * 0]
> +       stp     q2, q3, [\state, #16 * 2]
> +       stp     q4, q5, [\state, #16 * 4]
> +       stp     q6, q7, [\state, #16 * 6]
> +       stp     q8, q9, [\state, #16 * 8]
> +       stp     q10, q11, [\state, #16 * 10]
> +       stp     q12, q13, [\state, #16 * 12]
> +       stp     q14, q15, [\state, #16 * 14]
> +       stp     q16, q17, [\state, #16 * 16]
> +       stp     q18, q19, [\state, #16 * 18]
> +       stp     q20, q21, [\state, #16 * 20]
> +       stp     q22, q23, [\state, #16 * 22]
> +       stp     q24, q25, [\state, #16 * 24]
> +       stp     q26, q27, [\state, #16 * 26]
> +       stp     q28, q29, [\state, #16 * 28]
> +       stp     q30, q31, [\state, #16 * 30]!
> +       mrs     x\tmpnr, fpsr
> +       str     w\tmpnr, [\state, #16 * 2]
> +       mrs     x\tmpnr, fpcr
> +       str     w\tmpnr, [\state, #16 * 2 + 4]
> +.endm
> +
> +.macro fpsimd_restore_fpcr state, tmp
> +       /*
> +        * Writes to fpcr may be self-synchronising, so avoid restoring
> +        * the register if it hasn't changed.
> +        */
> +       mrs     \tmp, fpcr
> +       cmp     \tmp, \state
> +       b.eq    9999f
> +       msr     fpcr, \state
> +9999:
> +.endm
> +
> +/* Clobbers \state */
> +.macro fpsimd_restore state, tmpnr
> +       ldp     q0, q1, [\state, #16 * 0]
> +       ldp     q2, q3, [\state, #16 * 2]
> +       ldp     q4, q5, [\state, #16 * 4]
> +       ldp     q6, q7, [\state, #16 * 6]
> +       ldp     q8, q9, [\state, #16 * 8]
> +       ldp     q10, q11, [\state, #16 * 10]
> +       ldp     q12, q13, [\state, #16 * 12]
> +       ldp     q14, q15, [\state, #16 * 14]
> +       ldp     q16, q17, [\state, #16 * 16]
> +       ldp     q18, q19, [\state, #16 * 18]
> +       ldp     q20, q21, [\state, #16 * 20]
> +       ldp     q22, q23, [\state, #16 * 22]
> +       ldp     q24, q25, [\state, #16 * 24]
> +       ldp     q26, q27, [\state, #16 * 26]
> +       ldp     q28, q29, [\state, #16 * 28]
> +       ldp     q30, q31, [\state, #16 * 30]!
> +       ldr     w\tmpnr, [\state, #16 * 2]
> +       msr     fpsr, x\tmpnr
> +       ldr     w\tmpnr, [\state, #16 * 2 + 4]
> +       fpsimd_restore_fpcr x\tmpnr, \state
> +.endm
All the code above is just a verbatim copy of the Linux code which is 
GPLv2. To me, this is a clear violation of the license and may affect 
user of Unikraft (which is BSD).
Please rewrite the code or use code from a *BSD OS.

Cheers,

--
Julien Grall

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