Re: [PATCH 11/14] arm: implement remap interfaces needed for privcmd mappings.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Oct 04, 2012 at 04:11:52PM +0100, Ian Campbell wrote:
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> ---
>  arch/arm/xen/enlighten.c |   94 +++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 92 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index ba5cc13..9956af5 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -9,6 +9,7 @@
>  #include <xen/platform_pci.h>
>  #include <xen/xenbus.h>
>  #include <xen/page.h>
> +#include <xen/xen-ops.h>
>  #include <asm/xen/hypervisor.h>
>  #include <asm/xen/hypercall.h>
>  #include <linux/interrupt.h>
> @@ -18,6 +19,8 @@
>  #include <linux/of_irq.h>
>  #include <linux/of_address.h>
>  
> +#include <linux/mm.h>
> +
>  struct start_info _xen_start_info;
>  struct start_info *xen_start_info = &_xen_start_info;
>  EXPORT_SYMBOL_GPL(xen_start_info);
> @@ -43,15 +46,102 @@ EXPORT_SYMBOL_GPL(xen_platform_pci_unplug);
>  
>  static __read_mostly int xen_events_irq = -1;
>  
> +/* map fgmfn of domid to lpfn in the current domain */

<laughs> Say that really fast a couple of times :-)

Any way we can explain it a bit more of what each acronym means?

> +static int map_foreign_page(unsigned long lpfn, unsigned long fgmfn,
> +			    unsigned int domid)
> +{
> +	int rc;
> +	struct xen_add_to_physmap xatp = {
> +		.domid = DOMID_SELF,
> +		.u.foreign_domid = domid,
> +		.space = XENMAPSPACE_gmfn_foreign,
> +		.idx = fgmfn,
> +		.gpfn = lpfn,
> +	};
> +
> +	rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
> +	if (rc) {
> +		pr_warn("Failed to map pfn to mfn rc:%d pfn:%lx mfn:%lx\n",

How about 'Failed to map pfn (0x%lx) to mfn (0x%lx), rc: %d\n" ?

> +			rc, lpfn, fgmfn);
> +		return 1;
> +	}
> +	return 0;
> +}
> +
> +struct remap_data {
> +	unsigned long fgmfn; /* foreign domain's gmfn */

Shouldn't this be called now 'xen_pfn_t' or something.

> +	pgprot_t prot;
> +	domid_t  domid;
> +	struct vm_area_struct *vma;
> +	struct xen_remap_mfn_info *info;
> +};
> +
> +static int remap_pte_fn(pte_t *ptep, pgtable_t token, unsigned long addr,
> +			void *data)
> +{
> +	struct remap_data *info = data;
> +	struct xen_remap_mfn_info *savp = info->info;
> +	struct page *page = savp->pi_paga[savp->pi_next_todo++];
> +	unsigned long pfn = page_to_pfn(page);
> +	pte_t pte = pfn_pte(pfn, info->prot);
> +
> +	if (map_foreign_page(pfn, info->fgmfn, info->domid))
> +		return -EFAULT;
> +	set_pte_at(info->vma->vm_mm, addr, ptep, pte);
> +
> +	return 0;
> +}
> +
>  int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
>  			       unsigned long addr,
>  			       unsigned long mfn, int nr,
> -			       pgprot_t prot, unsigned domid)
> +			       pgprot_t prot, unsigned domid,
> +			       struct xen_remap_mfn_info *info)
>  {
> -	return -ENOSYS;
> +	int err;
> +	struct remap_data data;
> +
> +	/* TBD: Batching, current sole caller only does page at a time */
> +	if (nr > 1)

Lets also wrap it with WARN_ON?

> +		return -EINVAL;
> +
> +	data.fgmfn = mfn;
> +	data.prot = prot;
> +	data.domid = domid;
> +	data.vma = vma;
> +	data.info = info;
> +	err = apply_to_page_range(vma->vm_mm, addr, nr << PAGE_SHIFT,
> +				  remap_pte_fn, &data);
> +	return err;
>  }
>  EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
>  
> +/* Returns: Number of pages unmapped */
> +int xen_unmap_domain_mfn_range(struct vm_area_struct *vma,
> +			       struct xen_remap_mfn_info *info)
> +{
> +	int count = 0;
> +
> +	while (info->pi_next_todo--) {
> +		struct xen_remove_from_physmap xrp;
> +		unsigned long rc, pfn;
> +
> +		pfn = page_to_pfn(info->pi_paga[info->pi_next_todo]);

Won't this miss the first pi_next_todo? You did the 'pi_next_todo--' so
will the compiler decrement it here in this operation or will it do
when it gets to the 'do' logic of the loop?

> +
> +		xrp.domid = DOMID_SELF;
> +		xrp.gpfn = pfn;
> +		rc = HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrp);

'rc' is 'unsigned long'. Is that right? You don't want it to be 'int'?

> +		if (rc) {
> +			pr_warn("Failed to unmap pfn:%lx rc:%ld\n",
> +				pfn, rc);
> +			return count;
> +		}
> +		count++;
> +	}
> +	return count;
> +}
> +EXPORT_SYMBOL_GPL(xen_unmap_domain_mfn_range);
> +
>  /*
>   * see Documentation/devicetree/bindings/arm/xen.txt for the
>   * documentation of the Xen Device Tree format.
> -- 
> 1.7.2.5