On Thu, Sep 23, 2021 at 02:07:52PM +0530, Jeya R wrote:
> fastrpc_put_args is copying all the output buffers to user. For large
> number of output context buffers, this might cause performance
> degradation. Copying is not needed for DMA-BUF heap buffers.
What does "performance degradation" really mean?
>
> Signed-off-by: Jeya R <jeyr@xxxxxxxxxxxxxx>
> ---
> drivers/misc/fastrpc.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index beda610..536eabf 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -890,15 +890,17 @@ static int fastrpc_put_args(struct fastrpc_invoke_ctx *ctx,
> inbufs = REMOTE_SCALARS_INBUFS(ctx->sc);
>
> for (i = inbufs; i < ctx->nbufs; ++i) {
> - void *src = (void *)(uintptr_t)rpra[i].pv;
> - void *dst = (void *)(uintptr_t)ctx->args[i].ptr;
> - u64 len = rpra[i].len;
> + if (!ctx->maps[i]) {
> + void *src = (void *)(uintptr_t)rpra[i].pv;
> + void *dst = (void *)(uintptr_t)ctx->args[i].ptr;
uintptr_t is not a kernel variable type. Please use the real kernel
type for this as you are touching these lines.
> + u64 len = rpra[i].len;
>
> - if (!kernel) {
> - if (copy_to_user((void __user *)dst, src, len))
> - return -EFAULT;
> - } else {
> - memcpy(dst, src, len);
> + if (!kernel) {
> + if (copy_to_user((void __user *)dst, src, len))
> + return -EFAULT;
> + } else {
> + memcpy(dst, src, len);
> + }
So you were copying buffers that didn't need to be copied? So you are
now doing less work? Or is this fixing a bug where you were copying
things that you should not have been copying?
What commit does this fix? Does this need to go to the stable kernel
trees?
thanks,
greg k-h
