[Xen-devel] [RFC 17/23] xen/grant-table: Make it running on 64KB granularity

[Julien Grall <julien.grall@xxxxxxxxxx>]

The Xen interface is using 4KB page granularity. This means that each
grant is 4KB.

The current implementation allocates a Linux page per grant. On Linux
using 64KB page granularity, only the first 4KB of the page will be
used.

We could decrease the memory wasted by sharing the page with multiple
grant. It will require some care with the {Set,Clear}ForeignPage macro.

Note that no changes has been made in the x86 code because both Linux
and Xen will only use 4KB page granularity.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
---
 arch/arm/xen/p2m.c        | 6 +++---
 drivers/xen/grant-table.c | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm/xen/p2m.c b/arch/arm/xen/p2m.c
index 887596c..0ed01f2 100644
--- a/arch/arm/xen/p2m.c
+++ b/arch/arm/xen/p2m.c
@@ -93,8 +93,8 @@ int set_foreign_p2m_mapping(struct gnttab_map_grant_ref 
*map_ops,
        for (i = 0; i < count; i++) {
                if (map_ops[i].status)
                        continue;
-               set_phys_to_machine(map_ops[i].host_addr >> PAGE_SHIFT,
-                                   map_ops[i].dev_bus_addr >> PAGE_SHIFT);
+               set_phys_to_machine(map_ops[i].host_addr >> XEN_PAGE_SHIFT,
+                                   map_ops[i].dev_bus_addr >> XEN_PAGE_SHIFT);
        }
 
        return 0;
@@ -108,7 +108,7 @@ int clear_foreign_p2m_mapping(struct gnttab_unmap_grant_ref 
*unmap_ops,
        int i;
 
        for (i = 0; i < count; i++) {
-               set_phys_to_machine(unmap_ops[i].host_addr >> PAGE_SHIFT,
+               set_phys_to_machine(unmap_ops[i].host_addr >> XEN_PAGE_SHIFT,
                                    INVALID_P2M_ENTRY);
        }
 
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 62f591f..dc0a787 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -642,7 +642,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
        if (xen_auto_xlat_grant_frames.count)
                return -EINVAL;
 
-       vaddr = xen_remap(addr, PAGE_SIZE * max_nr_gframes);
+       vaddr = xen_remap(addr, XEN_PAGE_SIZE * max_nr_gframes);
        if (vaddr == NULL) {
                pr_warn("Failed to ioremap gnttab share frames (addr=%pa)!\n",
                        &addr);
@@ -654,7 +654,7 @@ int gnttab_setup_auto_xlat_frames(phys_addr_t addr)
                return -ENOMEM;
        }
        for (i = 0; i < max_nr_gframes; i++)
-               pfn[i] = PFN_DOWN(addr) + i;
+               pfn[i] = XEN_PFN_DOWN(addr) + i;
 
        xen_auto_xlat_grant_frames.vaddr = vaddr;
        xen_auto_xlat_grant_frames.pfn = pfn;
@@ -978,7 +978,7 @@ static void gnttab_request_version(void)
 {
        /* Only version 1 is used, which will always be available. */
        grant_table_version = 1;
-       grefs_per_grant_frame = PAGE_SIZE / sizeof(struct grant_entry_v1);
+       grefs_per_grant_frame = XEN_PAGE_SIZE / sizeof(struct grant_entry_v1);
        gnttab_interface = &gnttab_v1_ops;
 
        pr_info("Grant tables using version %d layout\n", grant_table_version);
-- 
2.1.4


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