Messages in this thread | | | Date | Thu, 23 Sep 2021 10:49:23 +0200 | From | Greg KH <> | Subject | Re: [PATCH] misc: fastrpc: copy to user only for non-DMA-BUF heap buffers |
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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@codeaurora.org> > --- > 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
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