Messages in this thread | | | Subject | Re: [PATCHv3 10/17] x86/mm: Implement prep_encrypted_page() and arch_free_page() | From | Dave Hansen <> | Date | Wed, 13 Jun 2018 11:26:10 -0700 |
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On 06/12/2018 07:39 AM, Kirill A. Shutemov wrote: > prep_encrypted_page() also takes care about zeroing the page. We have to > do this after KeyID is set for the page.
This is an implementation detail that has gone unmentioned until now but has impacted at least half a dozen locations in previous patches. Can you rectify that, please?
> +void prep_encrypted_page(struct page *page, int order, int keyid, bool zero) > +{ > + int i; > + > + /* > + * The hardware/CPU does not enforce coherency between mappings of the > + * same physical page with different KeyIDs or encrypt ion keys.
What are "encrypt ion"s? :)
> + * We are responsible for cache management. > + * > + * We flush cache before allocating encrypted page > + */ > + clflush_cache_range(page_address(page), PAGE_SIZE << order); > + > + for (i = 0; i < (1 << order); i++) { > + WARN_ON_ONCE(lookup_page_ext(page)->keyid);
/* All pages coming out of the allocator should have KeyID 0 */
> + lookup_page_ext(page)->keyid = keyid; > + /* Clear the page after the KeyID is set. */ > + if (zero) > + clear_highpage(page); > + } > +}
How expensive is this?
> +void arch_free_page(struct page *page, int order) > +{ > + int i; >
/* KeyId-0 pages were not used for MKTME and need no work */
... or something
> + if (!page_keyid(page)) > + return;
Is page_keyid() optimized so that all this goes away automatically when MKTME is compiled out or unsupported?
> + for (i = 0; i < (1 << order); i++) { > + WARN_ON_ONCE(lookup_page_ext(page)->keyid > mktme_nr_keyids); > + lookup_page_ext(page)->keyid = 0; > + } > + > + clflush_cache_range(page_address(page), PAGE_SIZE << order); > +}
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