svn commit: r337774 - head/sys/amd64/amd64

[Konstantin Belousov]

Author: kib
Date: Tue Aug 14 17:14:33 2018
New Revision: 337774
URL: https://svnweb.freebsd.org/changeset/base/337774

Log:
  Reserve page at the physical address zero on amd64.
  
  We always zero the invalidated PTE/PDE for superpage, which means that
  L1TF CPU vulnerability (CVE-2018-3620) can be only used for reading
  from the page at zero.
  
  Note that both i386 and amd64 exclude the page from phys_avail[]
  array, so this change is redundant, but I think that phys_avail[] on
  UEFI-boot does not need to do that.  Eventually the blacklisting
  should be made conditional on CPUs which report that they are not
  vulnerable to L1TF.
  
  Reviewed by:	emaste. jhb
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/amd64/amd64/pmap.c

Modified: head/sys/amd64/amd64/pmap.c
==============================================================================
--- head/sys/amd64/amd64/pmap.c	Tue Aug 14 16:37:14 2018	(r337773)
+++ head/sys/amd64/amd64/pmap.c	Tue Aug 14 17:14:33 2018	(r337774)
@@ -1307,6 +1307,9 @@ pmap_init(void)
 	vm_size_t s;
 	int error, i, pv_npg, ret, skz63;
 
+	/* L1TF, reserve page @0 unconditionally */
+	vm_page_blacklist_add(0, bootverbose);
+
 	/* Detect bare-metal Skylake Server and Skylake-X. */
 	if (vm_guest == VM_GUEST_NO && cpu_vendor_id == CPU_VENDOR_INTEL &&
 	    CPUID_TO_FAMILY(cpu_id) == 0x6 && CPUID_TO_MODEL(cpu_id) == 0x55) {