On 04/07/12 07:49, zhenzhong.duan wrote:
> When populate pages across a mem boundary at bootup, the page count
> populated isn't correct. This is due to mem populated to non-mem
> region and ignored.
>
> Pfn range is also wrongly aligned when mem boundary isn't page aligned.
>
> Also need consider the rare case when xen_do_chunk fail(populate).
>
> For a dom0 booted with dom_mem=3368952K(0xcd9ff000-4k) dmesg diff is:
> [ 0.000000] Freeing 9e-100 pfn range: 98 pages freed
> [ 0.000000] 1-1 mapping on 9e->100
> [ 0.000000] 1-1 mapping on cd9ff->100000
> [ 0.000000] Released 98 pages of unused memory
> [ 0.000000] Set 206435 page(s) to 1-1 mapping
> -[ 0.000000] Populating cd9fe-cda00 pfn range: 1 pages added
> +[ 0.000000] Populating cd9fe-cd9ff pfn range: 1 pages added
> +[ 0.000000] Populating 100000-100061 pfn range: 97 pages added
> [ 0.000000] BIOS-provided physical RAM map:
> [ 0.000000] Xen: 0000000000000000 - 000000000009e000 (usable)
> [ 0.000000] Xen: 00000000000a0000 - 0000000000100000 (reserved)
> [ 0.000000] Xen: 0000000000100000 - 00000000cd9ff000 (usable)
> [ 0.000000] Xen: 00000000cd9ffc00 - 00000000cda53c00 (ACPI NVS)
> ...
> [ 0.000000] Xen: 0000000100000000 - 0000000100061000 (usable)
> [ 0.000000] Xen: 0000000100061000 - 000000012c000000 (unusable)
> ...
> [ 0.000000] MEMBLOCK configuration:
> ...
> -[ 0.000000] reserved[0x4] [0x000000cd9ff000-0x000000cd9ffbff], 0xc00 bytes
> -[ 0.000000] reserved[0x5] [0x00000100000000-0x00000100060fff], 0x61000 bytes
>
> Related xen memory layout:
> (XEN) Xen-e820 RAM map:
> (XEN) 0000000000000000 - 000000000009ec00 (usable)
> (XEN) 00000000000f0000 - 0000000000100000 (reserved)
> (XEN) 0000000000100000 - 00000000cd9ffc00 (usable)
>
> Signed-off-by: Zhenzhong Duan <zhenzhong.duan@xxxxxxxxxx>
> ---
> arch/x86/xen/setup.c | 24 +++++++++++-------------
> 1 files changed, 11 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index a4790bf..bd78773 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -157,50 +157,48 @@ static unsigned long __init xen_populate_chunk(
> unsigned long dest_pfn;
>
> for (i = 0, entry = list; i < map_size; i++, entry++) {
> - unsigned long credits = credits_left;
> unsigned long s_pfn;
> unsigned long e_pfn;
> unsigned long pfns;
> long capacity;
>
> - if (credits <= 0)
> + if (credits_left <= 0)
> break;
>
> if (entry->type != E820_RAM)
> continue;
>
> - e_pfn = PFN_UP(entry->addr + entry->size);
> + e_pfn = PFN_DOWN(entry->addr + entry->size);
Ok.
>
> /* We only care about E820 after the xen_start_info->nr_pages */
> if (e_pfn <= max_pfn)
> continue;
>
> - s_pfn = PFN_DOWN(entry->addr);
> + s_pfn = PFN_UP(entry->addr);
Ok.
> /* If the E820 falls within the nr_pages, we want to start
> * at the nr_pages PFN.
> * If that would mean going past the E820 entry, skip it
> */
> +again:
> if (s_pfn <= max_pfn) {
> capacity = e_pfn - max_pfn;
> dest_pfn = max_pfn;
> } else {
> - /* last_pfn MUST be within E820_RAM regions */
> - if (*last_pfn && e_pfn >= *last_pfn)
> - s_pfn = *last_pfn;
> capacity = e_pfn - s_pfn;
> dest_pfn = s_pfn;
> }
> - /* If we had filled this E820_RAM entry, go to the next one. */
> - if (capacity <= 0)
> - continue;
>
> - if (credits > capacity)
> - credits = capacity;
> + if (credits_left < capacity)
> + capacity = credits_left;
>
> - pfns = xen_do_chunk(dest_pfn, dest_pfn + credits, false);
> + pfns = xen_do_chunk(dest_pfn, dest_pfn + capacity, false);
> done += pfns;
> credits_left -= pfns;
> *last_pfn = (dest_pfn + pfns);
> + if (credits_left > 0 && *last_pfn < e_pfn) {
> + s_pfn = *last_pfn;
> + goto again;
> + }
This looks like it will loop forever if xen_do_chunk() repeatedly fails
because Xen is out of pages. I think if xen_do_chunk() cannot get a
page from Xen the repopulation process should stop -- aborting this
chunk and any others. This will allow the guest to continue to boot
just with less memory than expected.
David
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