[MODERATED] Re: [patch V11 15/16] SSB 15

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, May 02, 2018 at 11:51:17PM +0200, speck for Thomas Gleixner wrote:
> Subject: [patch V11 15/16] x86/process: Allow runtime control of Speculative Store Bypass
> From: Thomas Gleixner <tglx@linutronix.de>
> 
> The Speculative Store Bypass vulnerability can be mitigated with the
> Reduced Data Speculation (RDS) feature. To allow finer grained control of
> this eventually expensive mitigation a per task mitigation control is
> required.
> 
> Add a new TIF_RDS flag and put it into the group of TIF flags which are
> evaluated for mismatch in switch_to(). If these bits differ in the previous
> and the next task, then the slow path function __switch_to_xtra() is
> invoked. Implement the TIF_RDS dependent mitigation control in the slow
> path.
> 
> If the prctl for controlling Speculative Store Bypass is disabled or no
> task uses the prctl then there is no overhead in the switch_to() fast
> path.
> 
> Update the KVM related speculation control functions to take TID_RDS into
> account as well.
> 
> Based on a patch from Tim Chen. Completely rewritten.
> 
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

In case you want to add that ..