Re: [Xen-devel] [PATCH v2 5/5] libxc: create p2m list outside of kernel mapping if supported

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-10-02 at 07:49 +0200, Juergen Gross wrote:
>  
> +    /* Allocate p2m list if outside of initial kernel mapping. */
> +    if ( dom->arch_hooks->alloc_p2m_list && dom->parms.p2m_base != 
> UNSET_ADDR )
> +    {
> +        if ( dom->arch_hooks->alloc_p2m_list(dom) != 0 )
> +            goto err;
> +        dom->p2m_seg.vend = dom->p2m_seg.vend - dom->p2m_seg.vstart;
> +        dom->p2m_seg.vstart = dom->parms.p2m_base;
> +        dom->p2m_seg.vend += dom->p2m_seg.vstart;

Here is this strange pattern again.

It seems like you should be adding new APIs to the dom builder's VA/PA
allocation stuff and using those instead of working around the behaviour of
the existing ones.

> +    }
> +    /*
> +     * Build the page tables for mapping the p2m list at an address
> +     * specified by the to be loaded kernel.
> +     * l1pfn holds the pfn of the next page table to allocate.
> +     * At each level we might already have an entry filled when setting
> +     * up the initial kernel mapping. This can happen for the last entry
> +     * of each level only!
> +     */
> +    l3tab = NULL;
> +    l2tab = NULL;
> +    l1tab = NULL;
> +    l1pfn = round_pfn(dom->p2m_size * dom->arch_hooks->sizeof_pfn) +
> +            dom->p2m_seg.pfn;
> +
> +    for ( addr = dom->parms.p2m_base;
> +          addr < dom->parms.p2m_base +
> +                 dom->p2m_size * dom->arch_hooks->sizeof_pfn;
> +          addr += PAGE_SIZE_X86 )

This is replicating a bunch of existing setup_pgtable_* code.

Please refactor into a helper (one per PT layout) to map a region and use
that for the existing and new use cases.

> +    {
> +        if ( l3tab == NULL )
> +        {
> +            l4off = l4_table_offset_x86_64(addr);
> +            l3pfn = l4tab[l4off] ? l4pfn + dom->pg_l4 : l1pfn++;
> +            l3tab = xc_dom_pfn_to_ptr(dom, l3pfn, 1);
> +            if ( l3tab == NULL )
> +                goto pfn_error;
> +            l4tab[l4off] =
> +                pfn_to_paddr(xc_dom_p2m_guest(dom, l3pfn)) | L4_PROT;
> +        }
> +
> +        if ( l2tab == NULL )
> +        {
> +            l3off = l3_table_offset_x86_64(addr);
> +            l2pfn = l3tab[l3off] ? l3pfn + dom->pg_l3 : l1pfn++;
> +            l2tab = xc_dom_pfn_to_ptr(dom, l2pfn, 1);
> +            if ( l2tab == NULL )
> +                goto pfn_error;
> +            l3tab[l3off] =
> +                pfn_to_paddr(xc_dom_p2m_guest(dom, l2pfn)) | L3_PROT;
> +        }
> +
> +        if ( l1tab == NULL )
> +        {
> +            l2off = l2_table_offset_x86_64(addr);
> +            l1pfn = l2tab[l2off] ? l2pfn + dom->pg_l2 : l1pfn;
> +            l1tab = xc_dom_pfn_to_ptr(dom, l1pfn, 1);
> +            if ( l1tab == NULL )
> +                goto pfn_error;
> +            l2tab[l2off] =
> +                pfn_to_paddr(xc_dom_p2m_guest(dom, l1pfn)) | L2_PROT;
> +            l1pfn++;
> +        }
> +
> +        l1off = l1_table_offset_x86_64(addr);
> +        pgpfn = ((addr - dom->parms.p2m_base) >> PAGE_SHIFT_X86) +
> +                dom->p2m_seg.pfn;
> +        l1tab[l1off] =
> +            pfn_to_paddr(xc_dom_p2m_guest(dom, pgpfn)) | L1_PROT;
> +
> +        if ( l1off == (L1_PAGETABLE_ENTRIES_X86_64 - 1) )
> +        {
> +            l1tab = NULL;
> +            if ( l2off == (L2_PAGETABLE_ENTRIES_X86_64 - 1) )
> +            {
> +                l2tab = NULL;
> +                if ( l3off == (L3_PAGETABLE_ENTRIES_X86_64 - 1) )
> +                    l3tab = NULL;
> +            }
> +        }
> +    }
> +
>      return 0;
>  
>  pfn_error:
> @@ -442,6 +519,27 @@ pfn_error:
>  static int alloc_p2m_list(struct xc_dom_image *dom)
>  {
>      size_t p2m_alloc_size = dom->p2m_size * dom->arch_hooks->sizeof_pfn;
> +    xen_vaddr_t from, to;
> +    xen_pfn_t tables;
> +
> +    p2m_alloc_size = round_pg(p2m_alloc_size);
> +    if ( dom->parms.p2m_base != UNSET_ADDR )
> +    {
> +        /* Add space for page tables, 64 bit only. */

Please make an alloc_p2m_list_x86_64 which does this and then calls the
common code and then use the appropriate hook for each sub arch.


> +        from = dom->parms.p2m_base;
> +        to = from + p2m_alloc_size - 1;
> +        tables = 0;
> +        tables += nr_page_tables(dom, from, to,
> L4_PAGETABLE_SHIFT_X86_64);
> +        if ( to > (xen_vaddr_t)(~0ULL << L4_PAGETABLE_SHIFT_X86_64) )
> +            tables--;
> +        tables += nr_page_tables(dom, from, to,
> L3_PAGETABLE_SHIFT_X86_64);
> +        if ( to > (xen_vaddr_t)(~0ULL << L3_PAGETABLE_SHIFT_X86_64) )
> +            tables--;
> +        tables += nr_page_tables(dom, from, to,
> L2_PAGETABLE_SHIFT_X86_64);
> +        if ( to > (xen_vaddr_t)(~0ULL << L2_PAGETABLE_SHIFT_X86_64) )
> +            tables--;
> +        p2m_alloc_size += tables << PAGE_SHIFT_X86;
> +    }
>  
>      /* allocate phys2mach table */
>      if ( xc_dom_alloc_segment(dom, &dom->p2m_seg, "phys2mach",


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