Messages in this thread | | | Date | Thu, 17 Mar 2022 16:58:20 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCHv6 05/30] x86/tdx: Exclude shared bit from __PHYSICAL_MASK |
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On Thu, Mar 17, 2022 at 01:16:00AM +0100, Thomas Gleixner wrote: > On Wed, Mar 16 2022 at 05:08, Kirill A. Shutemov wrote: > > @@ -82,6 +82,14 @@ void __init tdx_early_init(void) > > > > cc_set_vendor(CC_VENDOR_INTEL); > > > > + /* > > + * All bits above GPA width are reserved and kernel treats shared bit > > + * as flag, not as part of physical address. > > + * > > + * Adjust physical mask to only cover valid GPA bits. > > + */ > > + physical_mask &= GENMASK_ULL(gpa_width - 2, 0); > > + > > Hrm. I forgot about the second use case for gpa_width, but my comment > about ordering still stands. OTOH: > > GENMASK_ULL(gpa_width - 2, 0) == BIT_UL(gpa_width - 1) - 1 > > right? So you really can consolidate on the fact that cc_mask is a > single bit which is above the guests physical address space boundary. > > I.e. make the code tell the story instead of adding lengthy comments > explaining the obfuscation.
So it will looks something like this:
cc_set_vendor(CC_VENDOR_INTEL); cc_mask = get_cc_mask(); cc_set_mask(cc_mask);
/* * All bits above GPA width are reserved and kernel treats shared bit * as flag, not as part of physical address. * * Adjust physical mask to only cover valid GPA bits. */ physical_mask &= cc_mask - 1;
I still think these comments are useful. I hided comment for cc_mask calclulation inside get_cc_mask().
Does it look fine to you?
-- Kirill A. Shutemov
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