On 12/21/2010 01:37 PM, Konrad Rzeszutek Wilk wrote:
> This patch prepares ourselves for the case where void entries in the P2M
> tree structure do not necessarily imply that the pages are missing.
> With this, we diligently set regions that will be used by the
> balloon driver to be INVALID_P2M_ENTRY and under the ownership
> of the balloon driver.
>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> ---
> arch/x86/xen/setup.c | 8 ++++++++
> drivers/xen/balloon.c | 1 +
> 2 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index b5a7f92..d984d36 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -52,6 +52,8 @@ phys_addr_t xen_extra_mem_start, xen_extra_mem_size;
>
> static __init void xen_add_extra_mem(unsigned long pages)
> {
> + unsigned long pfn;
> +
> u64 size = (u64)pages * PAGE_SIZE;
> u64 extra_start = xen_extra_mem_start + xen_extra_mem_size;
>
> @@ -66,6 +68,11 @@ static __init void xen_add_extra_mem(unsigned long pages)
> xen_extra_mem_size += size;
>
> xen_max_p2m_pfn = PFN_DOWN(extra_start + size);
> +
> + for (pfn = PFN_DOWN(extra_start); pfn <= xen_max_p2m_pfn; pfn++) {
> + BUG_ON(!set_phys_to_machine(pfn, INVALID_P2M_ENTRY));
Use __set_phys_to_machine where you don't expect (or can't allow) any
allocation.
Also, I'm not a fan of hiding real side-effectful code in a BUG_ON
predicate.
> + BUG_ON(get_phys_to_machine(pfn) != INVALID_P2M_ENTRY);
> + }
> }
>
> static unsigned long __init xen_release_chunk(phys_addr_t start_addr,
> @@ -105,6 +112,7 @@ static unsigned long __init xen_release_chunk(phys_addr_t
> start_addr,
> start, end, ret);
> if (ret == 1) {
> set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
Ditto on this one (I guess I forgot, or it predates the existence of
__set_phys_to_machine).
> + BUG_ON(get_phys_to_machine(pfn) != INVALID_P2M_ENTRY);
> len++;
> }
> }
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 43f9f02..f82bb48 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -297,6 +297,7 @@ static int decrease_reservation(unsigned long nr_pages)
> for (i = 0; i < nr_pages; i++) {
> pfn = mfn_to_pfn(frame_list[i]);
> set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
> + BUG_ON(get_phys_to_machine(pfn) != INVALID_P2M_ENTRY);
> balloon_append(pfn_to_page(pfn));
> }
>
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