Re: [Xen-devel] [PATCH 2/8] xen/balloon: Move common memory reservation routines to a module

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote:
> +
> +void xenmem_reservation_va_mapping_update(unsigned long count,
> +                                       struct page **pages,
> +                                       xen_pfn_t *frames)
> +{
> +#ifdef CONFIG_XEN_HAVE_PVMMU
> +     int i;
> +
> +     for (i = 0; i < count; i++) {
> +             struct page *page;
> +
> +             page = pages[i];
> +             BUG_ON(page == NULL);
> +
> +             /*
> +              * We don't support PV MMU when Linux and Xen is using
> +              * different page granularity.
> +              */
> +             BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
> +
> +             if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> +                     unsigned long pfn = page_to_pfn(page);
> +
> +                     set_phys_to_machine(pfn, frames[i]);
> +
> +                     /* Link back into the page tables if not highmem. */
> +                     if (!PageHighMem(page)) {
> +                             int ret;
> +
> +                             ret = HYPERVISOR_update_va_mapping(
> +                                             (unsigned long)__va(pfn << 
> PAGE_SHIFT),
> +                                             mfn_pte(frames[i], PAGE_KERNEL),
> +                                             0);
> +                             BUG_ON(ret);
> +                     }
> +             }
> +     }
> +#endif
> +}
> +EXPORT_SYMBOL(xenmem_reservation_va_mapping_update);
> +
> +void xenmem_reservation_va_mapping_reset(unsigned long count,
> +                                      struct page **pages)
> +{
> +#ifdef CONFIG_XEN_HAVE_PVMMU
> +     int i;
> +
> +     for (i = 0; i < count; i++) {
> +             /*
> +              * We don't support PV MMU when Linux and Xen is using
> +              * different page granularity.
> +              */
> +             BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
> +
> +             if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> +                     struct page *page = pages[i];
> +                     unsigned long pfn = page_to_pfn(page);
> +
> +                     if (!PageHighMem(page)) {
> +                             int ret;
> +
> +                             ret = HYPERVISOR_update_va_mapping(
> +                                             (unsigned long)__va(pfn << 
> PAGE_SHIFT),
> +                                             __pte_ma(0), 0);
> +                             BUG_ON(ret);
> +                     }
> +                     __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
> +             }
> +     }
> +#endif
> +}
> +EXPORT_SYMBOL(xenmem_reservation_va_mapping_reset);

One other thing I noticed --- both of these can be declared as NOPs in
the header file if !CONFIG_XEN_HAVE_PVMMU.

-boris

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