[Xen-devel] [PATCH v3 02/17] x86: do a revert of e871e80c38547d9faefc6604532ba3e985e65873

[Juergen Gross <jgross@xxxxxxxx>]

Revert "x86: allow Meltdown band-aid to be disabled" in order to
prepare for a final Meltdown mitigation.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 docs/misc/xen-command-line.markdown | 12 ------------
 xen/arch/x86/domain.c               |  7 ++-----
 xen/arch/x86/mm.c                   | 12 +-----------
 xen/arch/x86/smpboot.c              | 17 +++--------------
 xen/arch/x86/x86_64/entry.S         |  2 --
 5 files changed, 6 insertions(+), 44 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown 
b/docs/misc/xen-command-line.markdown
index 79feba6bcd..6df39dae0b 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1926,18 +1926,6 @@ In the case that x2apic is in use, this option switches 
between physical and
 clustered mode.  The default, given no hint from the **FADT**, is cluster
 mode.
 
-### xpti
-> `= <boolean>`
-
-> Default: `false` on AMD hardware
-> Default: `true` everywhere else
-
-Override default selection of whether to isolate 64-bit PV guest page
-tables.
-
-** WARNING: Not yet a complete isolation implementation, but better than
-nothing. **
-
 ### xsave
 > `= <boolean>`
 
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index f93327b0a2..752e0fafee 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1518,13 +1518,10 @@ void paravirt_ctxt_switch_from(struct vcpu *v)
 
 void paravirt_ctxt_switch_to(struct vcpu *v)
 {
-    root_pgentry_t *root_pgt = this_cpu(root_pgt);
     unsigned long cr4;
 
-    if ( root_pgt )
-        root_pgt[root_table_offset(PERDOMAIN_VIRT_START)] =
-            l4e_from_page(v->domain->arch.perdomain_l3_pg,
-                          __PAGE_HYPERVISOR_RW);
+    this_cpu(root_pgt)[root_table_offset(PERDOMAIN_VIRT_START)] =
+        l4e_from_page(v->domain->arch.perdomain_l3_pg, __PAGE_HYPERVISOR_RW);
 
     cr4 = pv_guest_cr4_to_real_cr4(v);
     if ( unlikely(cr4 != read_cr4()) )
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 35f204369b..fa0da7b0ff 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -3706,17 +3706,7 @@ long do_mmu_update(
                         break;
                     rc = mod_l4_entry(va, l4e_from_intpte(req.val), mfn,
                                       cmd == MMU_PT_UPDATE_PRESERVE_AD, v);
-                    /*
-                     * No need to sync if all uses of the page can be accounted
-                     * to the page lock we hold, its pinned status, and uses on
-                     * this (v)CPU.
-                     */
-                    if ( !rc && this_cpu(root_pgt) &&
-                         ((page->u.inuse.type_info & PGT_count_mask) >
-                          (1 + !!(page->u.inuse.type_info & PGT_pinned) +
-                           (pagetable_get_pfn(curr->arch.guest_table) == mfn) +
-                           (pagetable_get_pfn(curr->arch.guest_table_user) ==
-                            mfn))) )
+                    if ( !rc )
                         sync_guest = true;
                     break;
 
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 2ebef03027..49978b3697 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -331,7 +331,7 @@ void start_secondary(void *unused)
     spin_debug_disable();
 
     get_cpu_info()->xen_cr3 = 0;
-    get_cpu_info()->pv_cr3 = this_cpu(root_pgt) ? __pa(this_cpu(root_pgt)) : 0;
+    get_cpu_info()->pv_cr3 = __pa(this_cpu(root_pgt));
 
     load_system_tables();
 
@@ -740,20 +740,14 @@ static int clone_mapping(const void *ptr, root_pgentry_t 
*rpt)
     return 0;
 }
 
-static __read_mostly int8_t opt_xpti = -1;
-boolean_param("xpti", opt_xpti);
 DEFINE_PER_CPU(root_pgentry_t *, root_pgt);
 
 static int setup_cpu_root_pgt(unsigned int cpu)
 {
-    root_pgentry_t *rpt;
+    root_pgentry_t *rpt = alloc_xen_pagetable();
     unsigned int off;
     int rc;
 
-    if ( !opt_xpti )
-        return 0;
-
-    rpt = alloc_xen_pagetable();
     if ( !rpt )
         return -ENOMEM;
 
@@ -1002,14 +996,10 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
 
     stack_base[0] = stack_start;
 
-    if ( opt_xpti < 0 )
-        opt_xpti = boot_cpu_data.x86_vendor != X86_VENDOR_AMD;
-
     rc = setup_cpu_root_pgt(0);
     if ( rc )
         panic("Error %d setting up PV root page table\n", rc);
-    if ( per_cpu(root_pgt, 0) )
-        get_cpu_info()->pv_cr3 = __pa(per_cpu(root_pgt, 0));
+    get_cpu_info()->pv_cr3 = __pa(per_cpu(root_pgt, 0));
 
     set_nr_sockets();
 
@@ -1081,7 +1071,6 @@ void __init smp_prepare_boot_cpu(void)
 #endif
 
     get_cpu_info()->xen_cr3 = 0;
-    get_cpu_info()->pv_cr3 = 0;
 }
 
 static void
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 58f652d010..52f64cceda 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -50,7 +50,6 @@ restore_all_guest:
         movabs $DIRECTMAP_VIRT_START, %rcx
         mov   %rdi, %rax
         and   %rsi, %rdi
-        jz    .Lrag_keep_cr3
         and   %r9, %rsi
         add   %rcx, %rdi
         add   %rcx, %rsi
@@ -67,7 +66,6 @@ restore_all_guest:
         rep movsq
         mov   %r9, STACK_CPUINFO_FIELD(xen_cr3)(%rdx)
         write_cr3 rax, rdi, rsi
-.Lrag_keep_cr3:
 
         /* Restore stashed SPEC_CTRL value. */
         mov   %r15d, %eax
-- 
2.13.6


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