Messages in this thread | | | Date | Wed, 9 Aug 2023 09:13:48 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH] x86/tdx: Mark TSC reliable |
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On Wed, Aug 09, 2023 at 05:44:37AM +0000, Reshetova, Elena wrote: > > > > I don't know what the rules here. As far as I can see, all other clock > > sources relevant for TDX guest have lower rating. I guess we are fine? > > What about acpi_pm? > See this: > https://github.com/intel/tdx/commit/045692772ab4ef75062a83cc6e4ffa22cab40226
clocksource_acpi_pm.rating is 200 while TSC is 300.
> > There's notable exception to the rating order is kvmclock which is higher > > than tsc. It has to be disabled, but it is not clear to me how. This topic > > is related to how we are going to filter allowed devices/drivers, so I > > would postpone the decision until we settle on wider filtering schema. > > One option is to include "no-kvmclock" into kernel command line, which > is attested. Another option is to try to disable it explicitly, like we had > in past: > https://github.com/intel/tdx/commit/6b0357f2115c1bdd158c0c8836f4f541517bf375 > > The obvious issues with command line is that it is going to 1) grow > considerably if we try to disable everything we can via command line > and 2) there is a high chance that in practice people will not use secure default > and/or forget to verify the correct status of cmd line. But this is to be > expected I guess for any security method that involves attestation unfortunately.
I guess command line is fine, until we have coherent solution on filtering.
-- Kiryl Shutsemau / Kirill A. Shutemov
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