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SubjectRe: [Xen-devel] [PATCH] auto balloon initial domain and fix dom0_mem=X inconsistencies (v5).
On 03/05/12 16:15, David Vrabel wrote:
>
> xen: update VA mapping when releasing memory during setup
>
> In xen_memory_setup(), if a page that is being released has a VA
> mapping this must also be updated. Otherwise, the page will be not
> released completely -- it will still be referenced in Xen and won't be
> freed util the mapping is removed and this prevents it from being
> reallocated at a different PFN.
>
> This was already being done for the ISA memory region in
> xen_ident_map_ISA() but on many systems this was omitting a few pages
> as many systems marked a few pages below the ISA memory region as
> reserved in the e820 map.
>
> Signed-off-by: David Vrabel <david.vrabel@citrix.com>
> ---
[...]
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1929,29 +1929,6 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
> #endif
> }
>
> -void __init xen_ident_map_ISA(void)
> -{
> - unsigned long pa;
> -
> - /*
> - * If we're dom0, then linear map the ISA machine addresses into
> - * the kernel's address space.
> - */
> - if (!xen_initial_domain())
> - return;

It might look like this test has gone, however the new code which
updates the VA mapping uses the e820 map and for a domU its map will not
have a ISA region so there's no mapping to be updated.

David

> -
> - xen_raw_printk("Xen: setup ISA identity maps\n");
> -
> - for (pa = ISA_START_ADDRESS; pa < ISA_END_ADDRESS; pa += PAGE_SIZE) {
> - pte_t pte = mfn_pte(PFN_DOWN(pa), PAGE_KERNEL_IO);
> -
> - if (HYPERVISOR_update_va_mapping(PAGE_OFFSET + pa, pte, 0))
> - BUG();
> - }
> -
> - xen_flush_tlb();
> -}
> -
> static void __init xen_post_allocator_init(void)
> {
> pv_mmu_ops.set_pte = xen_set_pte;
> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
> index 506a3e6..d5f8714 100644
> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -139,6 +139,13 @@ static unsigned long __init xen_do_chunk(unsigned long start,
>
> return len;
> }
> +
> +static unsigned long __init xen_release_chunk(unsigned long start,
> + unsigned long end)
> +{
> + return xen_do_chunk(start, end, true);
> +}
> +
> static unsigned long __init xen_populate_chunk(
> const struct e820entry *list, size_t map_size,
> unsigned long max_pfn, unsigned long *last_pfn,
> @@ -197,6 +204,29 @@ static unsigned long __init xen_populate_chunk(
> }
> return done;
> }
> +
> +static void __init xen_set_identity_and_release_chunk(
> + unsigned long start_pfn, unsigned long end_pfn, unsigned long nr_pages,
> + unsigned long *released, unsigned long *identity)
> +{
> + unsigned long pfn;
> +
> + /*
> + * If the PFNs are currently mapped, the VA mapping also needs
> + * to be updated to be 1:1.
> + */
> + for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++)
> + (void)HYPERVISOR_update_va_mapping(
> + (unsigned long)__va(pfn << PAGE_SHIFT),
> + mfn_pte(pfn, PAGE_KERNEL_IO), 0);
> +
> + if (start_pfn < nr_pages)
> + *released += xen_release_chunk(
> + start_pfn, min(end_pfn, nr_pages));
> +
> + *identity += set_phys_range_identity(start_pfn, end_pfn);
> +}
> +
> static unsigned long __init xen_set_identity_and_release(
> const struct e820entry *list, size_t map_size, unsigned long nr_pages)
> {
> @@ -226,14 +256,11 @@ static unsigned long __init xen_set_identity_and_release(
> if (entry->type == E820_RAM)
> end_pfn = PFN_UP(entry->addr);
>
> - if (start_pfn < end_pfn) {
> - if (start_pfn < nr_pages)
> - released += xen_do_chunk(
> - start_pfn, min(end_pfn, nr_pages), true);
> + if (start_pfn < end_pfn)
> + xen_set_identity_and_release_chunk(
> + start_pfn, end_pfn, nr_pages,
> + &released, &identity);
>
> - identity += set_phys_range_identity(
> - start_pfn, end_pfn);
> - }
> start = end;
> }
> }
> diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
> index b095739..506fa08 100644
> --- a/arch/x86/xen/xen-ops.h
> +++ b/arch/x86/xen/xen-ops.h
> @@ -28,7 +28,6 @@ void xen_setup_shared_info(void);
> void xen_build_mfn_list_list(void);
> void xen_setup_machphys_mapping(void);
> pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
> -void xen_ident_map_ISA(void);
> void xen_reserve_top(void);
> extern unsigned long xen_max_p2m_pfn;
>



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