[Xen-changelog] [xen stable-4.6] x86/PV: don't zero-map LDT

[patchbot@xxxxxxx]

commit 566bfb1a00b3e3f6ed6610fe34a5b9ef42bcb81e
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Oct 29 13:45:05 2015 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 29 13:45:05 2015 +0100

    x86/PV: don't zero-map LDT
    
    This effectvely reverts the LDT related part of commit cf6d39f819
    ("x86/PV: properly populate descriptor tables"), which broke demand
    paged LDT handling in guests.
    
    Reported-by: David Vrabel <david.vrabel@xxxxxxxxxx>
    Diagnosed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Tested-by: David Vrabel <david.vrabel@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: 61031e64d3dafd2fb1953436444bf02eccb9b146
    master date: 2015-10-27 14:46:12 +0100
---
 xen/arch/x86/mm.c |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 327b837..8763414 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -508,7 +508,6 @@ static void invalidate_shadow_ldt(struct vcpu *v, int flush)
 {
     l1_pgentry_t *pl1e;
     unsigned int i;
-    unsigned long pfn, zero_pfn = PFN_DOWN(__pa(zero_page));
     struct page_info *page;
 
     BUG_ON(unlikely(in_irq()));
@@ -523,11 +522,10 @@ static void invalidate_shadow_ldt(struct vcpu *v, int 
flush)
 
     for ( i = 16; i < 32; i++ )
     {
-        pfn = l1e_get_pfn(pl1e[i]);
-        if ( !(l1e_get_flags(pl1e[i]) & _PAGE_PRESENT) || pfn == zero_pfn )
+        if ( !(l1e_get_flags(pl1e[i]) & _PAGE_PRESENT) )
             continue;
-        l1e_write(&pl1e[i], l1e_from_pfn(zero_pfn, __PAGE_HYPERVISOR_RO));
-        page = mfn_to_page(pfn);
+        page = l1e_get_page(pl1e[i]);
+        l1e_write(&pl1e[i], l1e_empty());
         ASSERT_PAGE_IS_TYPE(page, PGT_seg_desc_page);
         ASSERT_PAGE_IS_DOMAIN(page, v->domain);
         put_page_and_type(page);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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