Re: [Xen-devel] [PATCH 2/3] Grant tables v2 implementation.

[annie li <annie.li@xxxxxxxxxx>]

On 2011-11-9 21:32, Ian Campbell wrote:

On Wed, 2011-11-09 at 08:15 +0000, annie.li@xxxxxxxxxx wrote:
  

From: Annie Li <annie.li@xxxxxxxxxx>

Receiver-side copying of packets is based on this implementation, it gives
better performance and better CPU accounting. It totally supports three types:
full-page, sub-page and transitive grants.

However this patch does not cover sub-page and transitive grants, it mainly
focus on Full-page part and implements grant table V2 interfaces corresponding
to what already exists in grant table V1, such as: grant table V2
initialization, mapping, releasing and exported interfaces.

Each guest can only supports one type of grant table type, every entry in grant
table should be the same version. It is necessary to set V1 or V2 version before
initializing the grant table.

Grant table exported interfaces of V2 are same with those of V1, Xen is
responsible to judge what grant table version guests are using in every grant
operation.

V2 fulfills the same role of V1, and it is totally backwards compitable with V1.
If dom0 support grant table V2, the guests runing on it can run with either V1
or V2.

Signed-off-by: Annie Li <annie.li@xxxxxxxxxx>
---
 arch/x86/xen/grant-table.c |   34 ++++++++-
 drivers/xen/grant-table.c  |  194 +++++++++++++++++++++++++++++++++++++++++---
 include/xen/grant_table.h  |    6 +-
 3 files changed, 220 insertions(+), 14 deletions(-)

diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index 65ce508..3e9f936 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -54,6 +54,17 @@ static int map_pte_fn(pte_t *pte, struct page *pmd_page,
        return 0;
 }

+/*32bits is not enough since Xen supports sparse physical memory*/
    

What does this mean?
  

Sorry for the confusion, my comment seems not so precise.
This function is used to map the status frames of grant table 2, and the status definition is uint64_t. So it requires 64bits even on both 32bit guest.

+static int map_pte_fn_status(pte_t *pte, struct page *pmd_page,
+                            unsigned long addr, void *data)
+{
+       uint64_t **frames = (uint64_t **)data;
+
+       set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));
+       (*frames)++;
+       return 0;
+}
    

Isn't this function identical to map_pte_fn?

  

Yes, map_pte_fn already exists, but the frames definition is different.

uint64_t **frames in map_pte_fn_status  VS unsigned long **frames in map_pte_fn

Grant table 2 added status frames which is defined as uint64_t, so I kept both map_pte_fn and map_pte_fn_status.

+
 static int unmap_pte_fn(pte_t *pte, struct page *pmd_page,
                        unsigned long addr, void *data)
 {
    

@@ -630,6 +756,44 @@ static int gnttab_map_status_v1(unsigned int nr_gframes)
        return 0;
 }

+static int gnttab_map_status_v2(unsigned int nr_gframes)
+{
+       uint64_t *sframes;
+       unsigned int nr_sframes;
+       struct gnttab_get_status_frames getframes;
+       int rc;
+
+       nr_sframes = nr_status_frames(nr_gframes);
+
+       /* No need for kzalloc as it is initialized in following hyercall
    

                                                                   hypercall
  

Thanks, will fix it.

+        * GNTTABOP_get_status_frames.
+        */
+       sframes = kmalloc(nr_sframes  * sizeof(uint64_t), GFP_ATOMIC);
+       if (!sframes)
+               return -ENOMEM;
+
+       getframes.dom        = DOMID_SELF;
+       getframes.nr_frames  = nr_sframes;
+       set_xen_guest_handle(getframes.frame_list, sframes);
+
+       rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
+                                      &getframes, 1);
+       if (rc == -ENOSYS) {
+               kfree(sframes);
+               return -ENOSYS;
+       }
+
+       BUG_ON(rc || getframes.status);
+
+       rc = arch_gnttab_map_status(sframes, nr_sframes,
+                                   nr_status_frames(gnttab_max_grant_frames()),
+                                   &grstatus);
+       BUG_ON(rc);
+       kfree(sframes);
+
+       return 0;
+}
+
 static int gnttab_map_status(unsigned int nr_gframes)
 {
        return gnttab_interface._gnttab_map_status(nr_gframes);
@@ -666,6 +830,9 @@ static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
                return rc;
        }

+       /* No need for kzalloc as it is initialized in following hyercall
    

"hypercall" again
  

Thanks, will fix it.

Thanks
Annie

Ian.


  

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