On Thu, Jun 18, 2020 at 08:38:06AM -0700, Dave Hansen wrote:
On 6/18/20 8:26 AM, Andersen, John wrote:
On Thu, Jun 18, 2020 at 07:41:04AM -0700, Dave Hansen wrote:
+config PARAVIRT_CR_PIN
bool "Paravirtual bit pinning for CR0 and CR4"depends on KVM_GUESThelpSelect this option to have the virtualised guest request that thehypervisor disallow it from disabling protections set in controlregisters. The hypervisor will prevent exploits from disablingfeatures such as SMEP, SMAP, UMIP, and WP.I'm confused. Does this add support for ""Paravirtual bit pinning", or actually tell the guest to request pinning by default?
It says "Select this option to have the virtualised guest request...", which makes it sound like it affects the default rather than the availability of the option.
How about this
Select this option to request protection of SMEP, SMAP, UMIP, and WP control register bits when running paravirtualized under KVM. Protection will be active provided the feature is available host side and kexec is disabled via kconfig or the command line for the guest requesting protection.
It still isn't very clear to me.
Let's pull the config option out of this patch. Enable the feature by default and do the command-line processing in this patch.
If you still think a Kconfig option is helpful, add it in a separate patch calling out the deficiencies with the boot-time options.
That's right we're going to pull it out anyway and just disable if the disable_pv_cr_pin command line option is set. Oops. That solves that.
Thank you very much for your review Dave