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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/xen: do not identity map E820 memory regions that are UNUSABLE
On 09/07/13 14:38, David Vrabel wrote:
> From: David Vrabel <david.vrabel@xxxxxxxxxx>
>
> If there are UNUSABLE regions in the machine memory map, dom0 will
> attempt to map them 1:1 which is not permitted by Xen and the kernel
> will crash.
>
> There isn't anything interesting in the UNUSABLE region that the dom0
> kernel needs access to so we can avoid making the 1:1 mapping and
> leave the region as RAM.
>
> Since the obtaining the memory map for dom0 and domU are now more
> different, refactor each into separate functions.
>
> This fixes a dom0 boot failure if tboot is used (because tboot was
> marking a memory region as UNUSABLE).
>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
I tested it with Xen 4.1.3-rc and Linux 3.8.13.4 and it is fixing the
early boot crash I reported.
Tested-by: Aurelien Chartier <aurelien.chartier@xxxxxxxxxx>
> ---
> arch/x86/xen/setup.c | 114
> ++++++++++++++++++++++++++++++++++++++++----------
> 1 files changed, 91 insertions(+), 23 deletions(-)
>
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index 94eac5c..3fdb6bd 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -55,6 +55,91 @@ unsigned long xen_released_pages;
> */
> #define EXTRA_MEM_RATIO (10)
>
> +static int __init xen_get_memory_map_dom0(struct e820entry *map,
> + unsigned *nr_entries)
> +{
> + struct xen_memory_map memmap;
> + unsigned i;
> + int ret;
> +
> + /*
> + * Dom0 requires access to machine addresses for BIOS data and
> + * MMIO (e.g. PCI) devices. The reset of the kernel expects
> + * to be able to access these through a 1:1 p2m mapping.
> + *
> + * We need to take the pseudo physical memory map and set up
> + * 1:1 mappings corresponding to the RESERVED regions and
> + * holes in the /machine/ memory map, adding/expanding the RAM
> + * region at the end of the map for the relocated RAM.
> + *
> + * This is more easily done if we just start with the machine
> + * memory map.
> + *
> + * UNUSABLE regions are awkward, they are not interesting to
> + * dom0 and Xen won't allow them to be mapped so we want to
> + * leave these as RAM in the pseudo physical map.
> + *
> + * Again, this is easiest if we take the machine memory map
> + * and change the UNUSABLE regions to RAM.
> + */
> +
> + memmap.nr_entries = *nr_entries;
> + set_xen_guest_handle(memmap.buffer, map);
> +
> + ret = HYPERVISOR_memory_op(XENMEM_machine_memory_map, &memmap);
> + if (ret < 0)
> + return ret;
> +
> + for (i = 0; i < memmap.nr_entries; i++) {
> + if (map[i].type == E820_UNUSABLE)
> + map[i].type = E820_RAM;
> + }
> +
> + *nr_entries = memmap.nr_entries;
> + return 0;
> +}
> +
> +static int __init xen_get_memory_map_domu(struct e820entry *map,
> + unsigned *nr_entries)
> +{
> + struct xen_memory_map memmap;
> + int ret;
> +
> + /*
> + * For domUs, use the psuedo-physical memory map.
Small typo here.
> + *
> + * If this is not available, fake up a memory map with a
> + * single region containing the initial number of pages.
> + */
> +
> + memmap.nr_entries = *nr_entries;
> + set_xen_guest_handle(memmap.buffer, map);
> +
> + ret = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
> + if (ret == -ENOSYS) {
> + unsigned long max_pfn = min(MAX_DOMAIN_PAGES,
> + xen_start_info->nr_pages);
> + memmap.nr_entries = 1;
> + map[0].addr = 0ULL;
> + map[0].size = PFN_PHYS(max_pfn);
> + /* 8MB slack (to balance backend allocations). */
> + map[0].size += 8ULL << 20;
> + map[0].type = E820_RAM;
> + } else if (ret < 0)
> + return ret;
> +
> + *nr_entries = memmap.nr_entries;
> + return 0;
> +}
> +
> +static int __init xen_get_memory_map(struct e820entry *map, unsigned
> *nr_entries)
> +{
> + if (xen_initial_domain())
> + return xen_get_memory_map_dom0(map, nr_entries);
> + else
> + return xen_get_memory_map_domu(map, nr_entries);
> +}
> +
> static void __init xen_add_extra_mem(u64 start, u64 size)
> {
> unsigned long pfn;
> @@ -319,42 +404,25 @@ static void xen_align_and_add_e820_region(u64 start,
> u64 size, int type)
> char * __init xen_memory_setup(void)
> {
> static struct e820entry map[E820MAX] __initdata;
> + unsigned map_nr_entries = E820MAX;
>
> unsigned long max_pfn = xen_start_info->nr_pages;
> unsigned long long mem_end;
> int rc;
> - struct xen_memory_map memmap;
> unsigned long max_pages;
> unsigned long last_pfn = 0;
> unsigned long extra_pages = 0;
> unsigned long populated;
> int i;
> - int op;
>
> max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);
> mem_end = PFN_PHYS(max_pfn);
>
> - memmap.nr_entries = E820MAX;
> - set_xen_guest_handle(memmap.buffer, map);
> -
> - op = xen_initial_domain() ?
> - XENMEM_machine_memory_map :
> - XENMEM_memory_map;
> - rc = HYPERVISOR_memory_op(op, &memmap);
> - if (rc == -ENOSYS) {
> - BUG_ON(xen_initial_domain());
> - memmap.nr_entries = 1;
> - map[0].addr = 0ULL;
> - map[0].size = mem_end;
> - /* 8MB slack (to balance backend allocations). */
> - map[0].size += 8ULL << 20;
> - map[0].type = E820_RAM;
> - rc = 0;
> - }
> + rc = xen_get_memory_map(map, &map_nr_entries);
> BUG_ON(rc);
>
> /* Make sure the Xen-supplied memory map is well-ordered. */
> - sanitize_e820_map(map, memmap.nr_entries, &memmap.nr_entries);
> + sanitize_e820_map(map, map_nr_entries, &map_nr_entries);
>
> max_pages = xen_get_max_pages();
> if (max_pages > max_pfn)
> @@ -366,12 +434,12 @@ char * __init xen_memory_setup(void)
> * this are first released.
> */
> xen_released_pages = xen_set_identity_and_release(
> - map, memmap.nr_entries, max_pfn);
> + map, map_nr_entries, max_pfn);
>
> /*
> * Populate back the non-RAM pages and E820 gaps that had been
> * released. */
> - populated = xen_populate_chunk(map, memmap.nr_entries,
> + populated = xen_populate_chunk(map, map_nr_entries,
> max_pfn, &last_pfn, xen_released_pages);
>
> xen_released_pages -= populated;
> @@ -395,7 +463,7 @@ char * __init xen_memory_setup(void)
> extra_pages = min(EXTRA_MEM_RATIO * min(max_pfn, PFN_DOWN(MAXMEM)),
> extra_pages);
> i = 0;
> - while (i < memmap.nr_entries) {
> + while (i < map_nr_entries) {
> u64 addr = map[i].addr;
> u64 size = map[i].size;
> u32 type = map[i].type;
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