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Date: Mon, 7 May 2012 14:48:08 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: David Vrabel <david.vrabel@...rix.com>
Cc: "xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"JBeulich@...e.com" <JBeulich@...e.com>
Subject: Re: [Xen-devel] [PATCH] auto balloon initial domain and fix
dom0_mem=X inconsistencies (v5).
On Thu, May 03, 2012 at 05:27:27PM +0100, David Vrabel wrote:
> 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@...rix.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.
What if you use e820_hole=1 and the pci=xx in the guest?
>
> 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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