x86/xen: don't write ptes directly in 32-bit PV guests

BugLink: https://bugs.launchpad.net/bugs/1835972
commit f7c90c2aa4004808dff777ba6ae2c7294dd06851 upstream.

In some cases 32-bit PAE PV guests still write PTEs directly instead of
using hypercalls. This is especially bad when clearing a PTE as this is
done via 32-bit writes which will produce intermediate L1TF attackable
PTEs.

Change the code to use hypercalls instead.

Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index 0b99078dbd92f8d7926b6e6b118ef94252af2585..a8975b239f6c49bc919ee6fa3faedb58f1d7d173 100644 (file)
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -425,14 +425,13 @@ static void xen_set_pud(pud_t *ptr, pud_t val)
 static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
 {
        trace_xen_mmu_set_pte_atomic(ptep, pte);
-       set_64bit((u64 *)ptep, native_pte_val(pte));
+       __xen_set_pte(ptep, pte);
 }
 
 static void xen_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
 {
        trace_xen_mmu_pte_clear(mm, addr, ptep);
-       if (!xen_batched_set_pte(ptep, native_make_pte(0)))
-               native_pte_clear(mm, addr, ptep);
+       __xen_set_pte(ptep, native_make_pte(0));
 }
 
 static void xen_pmd_clear(pmd_t *pmdp)
@@ -1542,7 +1541,7 @@ static void __init xen_set_pte_init(pte_t *ptep, pte_t pte)
                pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) &
                               pte_val_ma(pte));
 #endif
-       native_set_pte(ptep, pte);
+       __xen_set_pte(ptep, pte);
 }
 
 /* Early in boot, while setting up the initial pagetable, assume