svn commit: r321924 - head/sys/amd64/cloudabi64

[Ed Schouten]

Author: ed
Date: Wed Aug  2 13:08:10 2017
New Revision: 321924
URL: https://svnweb.freebsd.org/changeset/base/321924

Log:
  Keep top page on CloudABI to work around AMD Ryzen stability issues.
  
  Similar to r321899, reduce sv_maxuser by one page inside of CloudABI.
  This ensures that the stack, the vDSO and any allocations cannot touch
  the top page of user virtual memory.
  
  Considering that CloudABI userspace is completely oblivious to virtual
  memory layout, don't bother making this conditional based on the CPU of
  the running system.
  
  Reviewed by:	kib, truckman
  Differential Revision:	https://reviews.freebsd.org/D11808

Modified:
  head/sys/amd64/cloudabi64/cloudabi64_sysvec.c

Modified: head/sys/amd64/cloudabi64/cloudabi64_sysvec.c
==============================================================================
--- head/sys/amd64/cloudabi64/cloudabi64_sysvec.c	Wed Aug  2 12:31:03 2017	(r321923)
+++ head/sys/amd64/cloudabi64/cloudabi64_sysvec.c	Wed Aug  2 13:08:10 2017	(r321924)
@@ -199,7 +199,8 @@ static struct sysentvec cloudabi64_elf_sysvec = {
 	.sv_coredump		= elf64_coredump,
 	.sv_pagesize		= PAGE_SIZE,
 	.sv_minuser		= VM_MIN_ADDRESS,
-	.sv_maxuser		= VM_MAXUSER_ADDRESS,
+	/* Keep top page reserved to work around AMD Ryzen stability issues. */
+	.sv_maxuser		= VM_MAXUSER_ADDRESS - PAGE_SIZE,
 	.sv_stackprot		= VM_PROT_READ | VM_PROT_WRITE,
 	.sv_copyout_strings	= cloudabi64_copyout_strings,
 	.sv_setregs		= cloudabi64_proc_setregs,