Re: [Xen-devel] linux PVH broken in 3.16.0-rc7 (arch_gnttab_map_shared)

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 02/08/14 00:46, Mukesh Rathor wrote:
> Hi,
> 
> Not sure if this already got reported, but it appears 
> 
> commit b7dd0e3
> Author: David Vrabel <david.vrabel@xxxxxxxxxx>
> Date:   Fri Jul 11 16:42:34 2014 +0100
> 
>     x86/xen: safely map and unmap grant frames when in atomic context
> 
> has broken boot of domU PVH. The reason being arch_gnttab_map_shared
> is getting called before gnttab_shared_vm_area gets initialized by
> arch_gnttab_init(). As the comment says,
> 
> --->
> /* Call it _before_ __gnttab_init as we need to initialize the
>  *  * xen_auto_xlat_grant_frames first. */
> core_initcall(xen_pvh_gnttab_setup);
> <---
> 
> we can't wait till arch_gnttab_init is called by __gnttab_init().

Does this fix it?  I can't test it because the only box I have easily
available for testing is AMD.

David

8<--------------------------------
x86/xen: use vmap() to map grant table pages in PVH guests

Commit b7dd0e350e0b (x86/xen: safely map and unmap grant frames when
in atomic context) causes PVH guests to crash in
arch_gnttab_map_shared() when they attempted to map the pages for the
grant table.

This use of a PV-specific function during the PVH grant table setup is
non-obvious and not needed.  The standard vmap() function does the
right thing.

Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Reported-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
---
 arch/x86/xen/grant-table.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index ebfa9b2..767c9cb 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -168,6 +168,7 @@ static int __init xlated_setup_gnttab_pages(void)
 {
        struct page **pages;
        xen_pfn_t *pfns;
+       void *vaddr;
        int rc;
        unsigned int i;
        unsigned long nr_grant_frames = gnttab_max_grant_frames();
@@ -193,21 +194,20 @@ static int __init xlated_setup_gnttab_pages(void)
        for (i = 0; i < nr_grant_frames; i++)
                pfns[i] = page_to_pfn(pages[i]);
 
-       rc = arch_gnttab_map_shared(pfns, nr_grant_frames, nr_grant_frames,
-                                   &xen_auto_xlat_grant_frames.vaddr);
-
-       if (rc) {
+       vaddr = vmap(pages, nr_grant_frames, 0, PAGE_KERNEL);
+       if (!vaddr) {
                pr_warn("%s Couldn't map %ld pfns rc:%d\n", __func__,
                        nr_grant_frames, rc);
                free_xenballooned_pages(nr_grant_frames, pages);
                kfree(pages);
                kfree(pfns);
-               return rc;
+               return -ENOMEM;
        }
        kfree(pages);
 
        xen_auto_xlat_grant_frames.pfn = pfns;
        xen_auto_xlat_grant_frames.count = nr_grant_frames;
+       xen_auto_xlat_grant_frames.vaddr = vaddr;
 
        return 0;
 }
-- 
1.7.10.4


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