Re: [Xen-devel] xen.git branch reorg / success with 2.6.30-rc3 pv_ops dom0

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

Pasi, to validate the theory that you are seeing races between unpinning
and kmap_atomic_pte can you give this biguglystick approach to solving
it a go.

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 1729178..beeb8e8 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1145,9 +1145,12 @@ static int xen_unpin_page(struct mm_struct *mm, struct 
page *page,
        return 0;               /* never need to flush on unpin */
 }
 
+static DEFINE_SPINLOCK(hack_lock); /* Hack to sync unpin against 
kmap_atomic_pte */
+
 /* Release a pagetables pages back as normal RW */
 static void __xen_pgd_unpin(struct mm_struct *mm, pgd_t *pgd)
 {
+       spin_lock(&hack_lock);
        xen_mc_batch();
 
        xen_do_pin(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
@@ -1173,6 +1176,7 @@ static void __xen_pgd_unpin(struct mm_struct *mm, pgd_t 
*pgd)
        __xen_pgd_walk(mm, pgd, xen_unpin_page, USER_LIMIT);
 
        xen_mc_issue(0);
+       spin_unlock(&hack_lock);
 }
 
 static void xen_pgd_unpin(struct mm_struct *mm)
@@ -1521,6 +1525,9 @@ static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)
 static void *xen_kmap_atomic_pte(struct page *page, enum km_type type)
 {
        pgprot_t prot = PAGE_KERNEL;
+       void *ret;
+
+       spin_lock(&hack_lock);
 
        if (PagePinned(page))
                prot = PAGE_KERNEL_RO;
@@ -1530,7 +1537,11 @@ static void *xen_kmap_atomic_pte(struct page *page, enum 
km_type type)
                       page_to_pfn(page), type,
                       (unsigned long)pgprot_val(prot) & _PAGE_RW ? "WRITE" : 
"READ");
 
-       return kmap_atomic_prot(page, type, prot);
+       ret = kmap_atomic_prot(page, type, prot);
+
+       spin_unlock(&hack_lock);
+
+       return ret;
 }
 #endif
 



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