Re: [PATCH] x86/retpoline: Fill return stack buffer on vmexit

[Tom Lendacky <thomas.lendacky@amd.com>]

On 1/10/2018 5:47 PM, David Woodhouse wrote:
> On Wed, 2018-01-10 at 22:51 +0000, David Woodhouse wrote:
>> In accordance with the Intel and AMD documentation, we need to overwrite
>> all entries in the RSB on exiting a guest, to prevent malicious branch
>> target predictions from affecting the host kernel. This is needed both
>> for retpoline and for IBRS.
>>
>> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
>> ---
>> Untested in this form although it's a variant on what we've had already.
>> I have an army of machines willing to do my bidding but nested virt
>> is non-trivial and I figure I might as well post it as someone else
>> can probably test it in less than the time it takes me to work out how.
> 
> Now smoke tested with Intel VT-x, but not yet on AMD. Tom, would you be
> able to do that?

Yes, I'll try to get to it as soon as I can, but it might be tomorrow
(morning).

Thanks,
Tom

> 
> 
>> This implements the most pressing of the RSB stuffing documented
>> by dhansen (based our discussions) in https://goo.gl/pXbvBE