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    SubjectRe: [PATCHv4 17/18] x86/mm: Handle encrypted memory in page_to_virt() and __pa()
    From
    Date
    > diff --git a/arch/x86/include/asm/mktme.h b/arch/x86/include/asm/mktme.h
    > index ba83fba4f9b3..dbfbd955da98 100644
    > --- a/arch/x86/include/asm/mktme.h
    > +++ b/arch/x86/include/asm/mktme.h
    > @@ -29,6 +29,9 @@ void arch_free_page(struct page *page, int order);
    >
    > int sync_direct_mapping(void);
    >
    > +#define page_to_virt(x) \
    > + (__va(PFN_PHYS(page_to_pfn(x))) + page_keyid(x) * direct_mapping_size)

    Please put this in a generic header so that this hunk represents the
    *default* x86 implementation that is used universally on x86. Then,
    please do

    #ifndef CONFIG_MKTME_WHATEVER
    #define page_keyid(x) (0)
    #endif

    > #else
    > #define mktme_keyid_mask ((phys_addr_t)0)
    > #define mktme_nr_keyids 0
    > diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
    > index 53c32af895ab..ffad496aadad 100644
    > --- a/arch/x86/include/asm/page_64.h
    > +++ b/arch/x86/include/asm/page_64.h
    > @@ -23,7 +23,7 @@ static inline unsigned long __phys_addr_nodebug(unsigned long x)
    > /* use the carry flag to determine if x was < __START_KERNEL_map */
    > x = y + ((x > y) ? phys_base : (__START_KERNEL_map - PAGE_OFFSET));
    >
    > - return x;
    > + return x % direct_mapping_size;

    There are almost *surely* performance implications from this that affect
    anyone with this compile option turned on. There's now a 64-bit integer
    division operation which is used in places like kfree().

    That's a show-stopper for me until we've done some pretty comprehensive
    performance analysis of this, which means much more than one kernel
    compile test on one system.

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