[PATCH] x86: Cache write back at 32-bit entry point

[Park, Aiden]

Hi Bin,

> -----Original Message-----
> From: Bin Meng <bmeng.cn at gmail.com>
> Sent: Thursday, February 27, 2020 9:27 PM
> To: Park, Aiden <aiden.park at intel.com>
> Cc: masahiroy at kernel.org; sjg at chromium.org; sr at denx.de; agraf at suse.de; u-
> boot at lists.denx.de
> Subject: Re: [PATCH] x86: Cache write back at 32-bit entry point
> 
> Hi Aiden,
> 
> On Fri, Feb 28, 2020 at 12:54 PM Park, Aiden <aiden.park at intel.com> wrote:
> >
> > In a certain condition, invd causes cache coherence issue.
> >   1. Pre-stage boot code passes memory address to U-Boot
> >   2. The data of the memory address is still in data cache line
> >   3. The invd marks data cache line as invalid without write back
> >   4. U-Boot accesses the memory address
> >   5. Data is invalid
> >
> > Therefore, wbinvd is recommended at the 32-bit entry point even though
> > it consumes extra cpu clock cycles.
> >
> > Signed-off-by: Aiden Park <aiden.park at intel.com>
> > ---
> >  arch/x86/cpu/start.S | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> 
> This is already fixed (reverted) in the x86 tree. Would you please double check?
> 
Thank you for letting me know that. I think I missed some emails. Thanks again.
Andy, appreciate your commit. I had the same issue on Slim Bootloader due to this cache coherence.

> Regards,
> Bin

Best Regards,
Aiden