[MODERATED] Re: [PATCH 0/2] more sampling fun 0

On Wed, Feb 19, 2020 at 02:45:22PM -0800, speck for mark gross wrote:
> From: mark gross <[email protected]>
> Subject: [PATCH 0/2] Special Register Buffer Data Sampling patch set 
> 
> Special Register Buffer Data Sampling is a sampling type of vulnerability that
> leaks data across cores sharing the HW-RNG for vulnerable processors.
> 
> This leak is fixed by a microcode update and is enabled by default.
> 
> This new microcode serializes processor access during execution of RDRAND
> or RDSEED. It ensures that the shared buffer is overwritten before it
> is released for reuse.
> 
> The mitigation impacts the throughput of the RDRAND and RDSEED instructions
> and latency of RT processing running on the socket while executing RDRAND or
> RDSEED.  The micro bechmark of calling RDRAND many times shows a 10x slowdown.

Then we need to stop using RDRAND internally for our "give me a random
number api" which has spread to more and more parts of the kernel.

Here's a patch that does so:
	https://lore.kernel.org/lkml/[email protected]/
which I'm going to advise get merged now and backported to the stable
branches.

thanks,

greg k-h