Re: [Xen-devel] xen.git branch reorg / success with 2.6.30-rc3 pv_ops dom0

[Pasi Kärkkäinen <pasik@xxxxxx>]

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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