Merge tag 'stable/for-linus-4.0-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen bugfixes from David Vrabel:
 "Xen regression and bug fixes for 4.0-rc1

   - Fix two regressions introduced in 4.0-rc1 affecting PV/PVH guests
     in certain configurations.

   - Prevent pvscsi frontends bypassing backend checks.

   - Allow privcmd hypercalls to be preempted even on kernel with
     voluntary preemption.  This fixes soft-lockups with long running
     toolstack hypercalls (e.g., when creating/destroying large
     domains)"

* tag 'stable/for-linus-4.0-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  x86/xen: Initialize cr4 shadow for 64-bit PV(H) guests
  xen-scsiback: mark pvscsi frontend request consumed only after last read
  x86/xen: allow privcmd hypercalls to be preempted
  x86/xen: Make sure X2APIC_ENABLE bit of MSR_IA32_APICBASE is not set

3 files changed, 25 insertions, 1 deletions

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 000d4199b03e..31e2d5bf3e38 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -982,6 +982,9 @@ ENTRY(xen_hypervisor_callback)
 ENTRY(xen_do_upcall)
 1:      mov %esp, %eax
         call xen_evtchn_do_upcall
+#ifndef CONFIG_PREEMPT
+        call xen_maybe_preempt_hcall
+#endif
         jmp  ret_from_intr
         CFI_ENDPROC
 ENDPROC(xen_hypervisor_callback)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index db13655c3a2a..10074ad9ebf8 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1208,6 +1208,9 @@ ENTRY(xen_do_hypervisor_callback)   # do_hypervisor_callback(struct *pt_regs)
         popq %rsp
         CFI_DEF_CFA_REGISTER rsp
         decl PER_CPU_VAR(irq_count)
+#ifndef CONFIG_PREEMPT
+        call xen_maybe_preempt_hcall
+#endif
         jmp  error_exit
         CFI_ENDPROC
 END(xen_do_hypervisor_callback)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bd8b8459c3d0..5240f563076d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1070,6 +1070,23 @@ static inline void xen_write_cr8(unsigned long val)
         BUG_ON(val);
 }
 #endif
+
+static u64 xen_read_msr_safe(unsigned int msr, int *err)
+{
+        u64 val;
+
+        val = native_read_msr_safe(msr, err);
+        switch (msr) {
+        case MSR_IA32_APICBASE:
+#ifdef CONFIG_X86_X2APIC
+                if (!(cpuid_ecx(1) & (1 << (X86_FEATURE_X2APIC & 31))))
+#endif
+                        val &= ~X2APIC_ENABLE;
+                break;
+        }
+        return val;
+}
+
 static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
 {
         int ret;
@@ -1240,7 +1257,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 
         .wbinvd = native_wbinvd,
 
-        .read_msr = native_read_msr_safe,
+        .read_msr = xen_read_msr_safe,
         .write_msr = xen_write_msr_safe,
 
         .read_tsc = native_read_tsc,
@@ -1741,6 +1758,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 #ifdef CONFIG_X86_32
         i386_start_kernel();
 #else
+        cr4_init_shadow(); /* 32b kernel does this in i386_start_kernel() */
         x86_64_start_reservations((char *)__pa_symbol(&boot_params));
 #endif
 }