Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCHv6 05/30] x86/tdx: Exclude shared bit from __PHYSICAL_MASK | Date | Thu, 17 Mar 2022 15:39:08 +0100 |
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On Thu, Mar 17 2022 at 16:58, Kirill A. Shutemov wrote:
> 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?
Yes.
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