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drivers: xen: unmap Enlighten page before jumping to Linux
This commit fixes issue with usage of Xen hypervisor shared info page. Previously U-boot did not unmap it at the end of OS boot process. Xen did not prevent guest from this. So, it worked, but caused wierd issues - one memory page, that was returned by memalign in U-boot for Enlighten mapping was not unmaped by Xen (shared_info values was not removed from there) and returned to allocator. During the Linux boot, it uses shared_info page as regular RAM page, which leads to hypervisor shared info corruption. So, to fix this issue, as discussed on the xen-devel mailing list, the code should: 1) Unmap the page 2) Populate the area with memory using XENMEM_populate_physmap This patch adds page unmapping via XENMEM_remove_from_physmap, fills hole in address space where page was mapped via XENMEM_populate_physmap and return this address to memory allocator for freeing. Signed-off-by: Dmytro Firsov <dmytro_firsov@epam.com> Reviewed-by: Anastasiia Lukianenko <vicooodin@gmail.com>
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1 changed files with 31 additions and 0 deletions
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@ -144,6 +144,36 @@ struct shared_info *map_shared_info(void *p)
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return HYPERVISOR_shared_info;
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}
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void unmap_shared_info(void)
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{
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xen_pfn_t shared_info_pfn = virt_to_pfn(HYPERVISOR_shared_info);
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struct xen_remove_from_physmap xrfp = {0};
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struct xen_memory_reservation reservation = {0};
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xen_ulong_t nr_exts = 1;
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xrfp.domid = DOMID_SELF;
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xrfp.gpfn = shared_info_pfn;
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if (HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrfp) != 0)
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panic("Failed to unmap HYPERVISOR_shared_info\n");
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/*
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* After removing from physmap there will be a hole in address space on
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* HYPERVISOR_shared_info address, so to free memory allocated with
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* memalign and prevent exceptions during access to this page we need to
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* fill this 4KB hole with XENMEM_populate_physmap before jumping to Linux.
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*/
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reservation.domid = DOMID_SELF;
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reservation.extent_order = 0;
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reservation.address_bits = 0;
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set_xen_guest_handle(reservation.extent_start, &shared_info_pfn);
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reservation.nr_extents = nr_exts;
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if (HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation) != nr_exts)
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panic("Failed to populate memory on HYPERVISOR_shared_info addr\n");
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/* Now we can return this to memory allocator */
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free(HYPERVISOR_shared_info);
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}
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void do_hypervisor_callback(struct pt_regs *regs)
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{
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unsigned long l1, l2, l1i, l2i;
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@ -251,4 +281,5 @@ void xen_fini(void)
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fini_gnttab();
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fini_xenbus();
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fini_events();
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unmap_shared_info();
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}
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