From: Dmytro Firsov Date: Tue, 19 Jul 2022 14:55:28 +0000 (+0000) Subject: drivers: xen: unmap Enlighten page before jumping to Linux X-Git-Url: http://git.dujemihanovic.xyz/img/static/git-favicon.png?a=commitdiff_plain;h=0001a964b840a62c66da42a89a10a2656831aa4b;p=u-boot.git 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 Reviewed-by: Anastasiia Lukianenko --- diff --git a/drivers/xen/hypervisor.c b/drivers/xen/hypervisor.c index 2560894832..16c7c96c94 100644 --- a/drivers/xen/hypervisor.c +++ b/drivers/xen/hypervisor.c @@ -144,6 +144,36 @@ struct shared_info *map_shared_info(void *p) return HYPERVISOR_shared_info; } +void unmap_shared_info(void) +{ + xen_pfn_t shared_info_pfn = virt_to_pfn(HYPERVISOR_shared_info); + struct xen_remove_from_physmap xrfp = {0}; + struct xen_memory_reservation reservation = {0}; + xen_ulong_t nr_exts = 1; + + xrfp.domid = DOMID_SELF; + xrfp.gpfn = shared_info_pfn; + if (HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrfp) != 0) + panic("Failed to unmap HYPERVISOR_shared_info\n"); + + /* + * After removing from physmap there will be a hole in address space on + * HYPERVISOR_shared_info address, so to free memory allocated with + * memalign and prevent exceptions during access to this page we need to + * fill this 4KB hole with XENMEM_populate_physmap before jumping to Linux. + */ + reservation.domid = DOMID_SELF; + reservation.extent_order = 0; + reservation.address_bits = 0; + set_xen_guest_handle(reservation.extent_start, &shared_info_pfn); + reservation.nr_extents = nr_exts; + if (HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation) != nr_exts) + panic("Failed to populate memory on HYPERVISOR_shared_info addr\n"); + + /* Now we can return this to memory allocator */ + free(HYPERVISOR_shared_info); +} + void do_hypervisor_callback(struct pt_regs *regs) { unsigned long l1, l2, l1i, l2i; @@ -251,4 +281,5 @@ void xen_fini(void) fini_gnttab(); fini_xenbus(); fini_events(); + unmap_shared_info(); }