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SubjectRe: [PATCH v3 2/2] xen: modify kernel mappings corresponding to granted pages
On Wed, 7 Sep 2011, Konrad Rzeszutek Wilk wrote:
> > diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> > index 58efeb9..6c26ac80 100644
> > --- a/arch/x86/xen/p2m.c
> > +++ b/arch/x86/xen/p2m.c
> > @@ -161,7 +161,9 @@
> > #include <asm/xen/page.h>
> > #include <asm/xen/hypercall.h>
> > #include <asm/xen/hypervisor.h>
> > +#include <xen/grant_table.h>
> >
> > +#include "multicalls.h"
> > #include "xen-ops.h"
> >
> > static void __init m2p_override_init(void);
> > @@ -676,7 +678,8 @@ static unsigned long mfn_hash(unsigned long mfn)
> > }
> >
> > /* Add an MFN override for a particular page */
> > -int m2p_add_override(unsigned long mfn, struct page *page, bool clear_pte)
> > +int m2p_add_override(unsigned long mfn, struct page *page,
> > + struct gnttab_map_grant_ref *kmap_op)
>
> So how come you ripped out 'clear_pte' here but left it in
> m2p_remove_override? Is it b/c you aren't doing the pte_clear in
> the first place?

Because the "clear_pte" has been replaced with a proper update of the
kernel mappings for these pages. If the caller doesn't need that, it can
just pass NULL.


> Also there are other users of 'm2p_add_override' that you hadn't modified
> (blkback.c) so it will cause an compile failure.
>
> Please also test this patchset with the blkback in the picture to make
> sure this: cf8d91633ddef9e816ccbf3da833c79ce508988d
> does not happen.

I think I didn't find a compilation problem because false becomes NULL
with my compiler. Fixed now.


> > {
> > unsigned long flags;
> > unsigned long pfn;
> > @@ -699,9 +702,20 @@ int m2p_add_override(unsigned long mfn, struct page *page, bool clear_pte)
> > if (unlikely(!set_phys_to_machine(pfn, FOREIGN_FRAME(mfn))))
> > return -ENOMEM;
> >
> > - if (clear_pte && !PageHighMem(page))
> > - /* Just zap old mapping for now */
> > - pte_clear(&init_mm, address, ptep);
> > + if (kmap_op != NULL) {
> > + if (!PageHighMem(page)) {
> > + struct multicall_space mcs = xen_mc_entry(sizeof(*kmap_op));
> > +
> > + MULTI_grant_table_op(mcs.mc,
> > + GNTTABOP_map_grant_ref, kmap_op, 1);
> > +
> > + xen_mc_issue(PARAVIRT_LAZY_MMU);
> > + }
> > + page->private |= GRANT_FRAME_BIT;
> > + /* let's use dev_bus_addr to record the old mfn instead */
> > + kmap_op->dev_bus_addr = page->index;
> > + page->index = (unsigned long) kmap_op;
> > + }
> > spin_lock_irqsave(&m2p_override_lock, flags);
> > list_add(&page->lru, &m2p_overrides[mfn_hash(mfn)]);
> > spin_unlock_irqrestore(&m2p_override_lock, flags);
> > @@ -735,13 +749,44 @@ int m2p_remove_override(struct page *page, bool clear_pte)
> > spin_lock_irqsave(&m2p_override_lock, flags);
> > list_del(&page->lru);
> > spin_unlock_irqrestore(&m2p_override_lock, flags);
> > - set_phys_to_machine(pfn, page->index);
> >
> > - if (clear_pte && !PageHighMem(page))
> > - set_pte_at(&init_mm, address, ptep,
> > - pfn_pte(pfn, PAGE_KERNEL));
> > - /* No tlb flush necessary because the caller already
> > - * left the pte unmapped. */
> > + if (clear_pte) {
> > + struct gnttab_map_grant_ref *map_op =
> > + (struct gnttab_map_grant_ref *) page->index;
> > + set_phys_to_machine(pfn, map_op->dev_bus_addr);
> > + if (!PageHighMem(page)) {
> > + struct multicall_space mcs =
> > + xen_mc_entry(sizeof(struct gnttab_unmap_grant_ref));
> > + struct gnttab_unmap_grant_ref *unmap_op = mcs.args;
> > +
> > + /*
>
> scripts/checkpath.pl will throw a fit at the above.
>

right, fixed.


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