On Thu, Jun 11, 2009 at 10:18:34AM +0100, Ian Campbell wrote:
> Pasi, to validate the theory that you are seeing races between unpinning
> and kmap_atomic_pte can you give this biguglystick approach to solving
> it a go.
>
Guess what..
Now my dom0 didn't crash !! (with only this patch applied).
It survived kernel compilation just fine.. first time so far with pv_ops dom0.
I'll try again, just in case.
-- Pasi
> diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
> index 1729178..beeb8e8 100644
> --- a/arch/x86/xen/mmu.c
> +++ b/arch/x86/xen/mmu.c
> @@ -1145,9 +1145,12 @@ static int xen_unpin_page(struct mm_struct *mm, struct
> page *page,
> return 0; /* never need to flush on unpin */
> }
>
> +static DEFINE_SPINLOCK(hack_lock); /* Hack to sync unpin against
> kmap_atomic_pte */
> +
> /* Release a pagetables pages back as normal RW */
> static void __xen_pgd_unpin(struct mm_struct *mm, pgd_t *pgd)
> {
> + spin_lock(&hack_lock);
> xen_mc_batch();
>
> xen_do_pin(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
> @@ -1173,6 +1176,7 @@ static void __xen_pgd_unpin(struct mm_struct *mm, pgd_t
> *pgd)
> __xen_pgd_walk(mm, pgd, xen_unpin_page, USER_LIMIT);
>
> xen_mc_issue(0);
> + spin_unlock(&hack_lock);
> }
>
> static void xen_pgd_unpin(struct mm_struct *mm)
> @@ -1521,6 +1525,9 @@ static void xen_pgd_free(struct mm_struct *mm, pgd_t
> *pgd)
> static void *xen_kmap_atomic_pte(struct page *page, enum km_type type)
> {
> pgprot_t prot = PAGE_KERNEL;
> + void *ret;
> +
> + spin_lock(&hack_lock);
>
> if (PagePinned(page))
> prot = PAGE_KERNEL_RO;
> @@ -1530,7 +1537,11 @@ static void *xen_kmap_atomic_pte(struct page *page,
> enum km_type type)
> page_to_pfn(page), type,
> (unsigned long)pgprot_val(prot) & _PAGE_RW ? "WRITE" :
> "READ");
>
> - return kmap_atomic_prot(page, type, prot);
> + ret = kmap_atomic_prot(page, type, prot);
> +
> + spin_unlock(&hack_lock);
> +
> + return ret;
> }
> #endif
>
>
>
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