Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Thomas Gleixner:
 "A set of x86 specific fixes and updates:

   - The CR2 corruption fixes which store CR2 early in the entry code
     and hand the stored address to the fault handlers.

   - Revert a forgotten leftover of the dropped FSGSBASE series.

   - Plug a memory leak in the boot code.

   - Make the Hyper-V assist functionality robust by zeroing the shadow
     page.

   - Remove a useless check for dead processes with LDT

   - Update paravirt and VMware maintainers entries.

   - A few cleanup patches addressing various compiler warnings"

* 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/entry/64: Prevent clobbering of saved CR2 value
  x86/hyper-v: Zero out the VP ASSIST PAGE on allocation
  x86, boot: Remove multiple copy of static function sanitize_boot_params()
  x86/boot/compressed/64: Remove unused variable
  x86/boot/efi: Remove unused variables
  x86/mm, tracing: Fix CR2 corruption
  x86/entry/64: Update comments and sanity tests for create_gap
  x86/entry/64: Simplify idtentry a little
  x86/entry/32: Simplify common_exception
  x86/paravirt: Make read_cr2() CALLEE_SAVE
  MAINTAINERS: Update PARAVIRT_OPS_INTERFACE and VMWARE_HYPERVISOR_INTERFACE
  x86/process: Delete useless check for dead process with LDT
  x86: math-emu: Hide clang warnings for 16-bit overflow
  x86/e820: Use proper booleans instead of 0/1
  x86/apic: Silence -Wtype-limits compiler warnings
  x86/mm: Free sme_early_buffer after init
  x86/boot: Fix memory leak in default_get_smp_config()
  Revert "x86/ptrace: Prevent ptrace from clearing the FS/GS selector" and fix the test

1 files changed, 11 insertions, 2 deletions

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 0e033ef11a9f..0d258688c8cf 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -60,8 +60,17 @@ static int hv_cpu_init(unsigned int cpu)
 	if (!hv_vp_assist_page)
 		return 0;
 
-	if (!*hvp)
-		*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
+	/*
+	 * The VP ASSIST PAGE is an "overlay" page (see Hyper-V TLFS's Section
+	 * 5.2.1 "GPA Overlay Pages"). Here it must be zeroed out to make sure
+	 * we always write the EOI MSR in hv_apic_eoi_write() *after* the
+	 * EOI optimization is disabled in hv_cpu_die(), otherwise a CPU may
+	 * not be stopped in the case of CPU offlining and the VM will hang.
+	 */
+	if (!*hvp) {
+		*hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO,
+				 PAGE_KERNEL);
+	}
 
 	if (*hvp) {
 		u64 val;