kernel - Implement Errata 721 for 32-bit kernels too

* The AMD errata 721 definitely happens on cpus running in cpu bit mode
  but I got a weird kernel crash on 32-bit (which I don't have time to
  follow up) so I decided, what the heck, might as well do it on 32-bit
  boxes too.

diff --git a/sys/platform/pc32/i386/initcpu.c b/sys/platform/pc32/i386/initcpu.c
index 4854d43..6407f4e 100644 (file)
--- a/sys/platform/pc32/i386/initcpu.c
+++ b/sys/platform/pc32/i386/initcpu.c
@@ -636,6 +636,8 @@ init_686_amd(void)
 void
 initializecpu(void)
 {
+       uint64_t msr;
+
        switch (cpu) {
 #ifdef I486_CPU
        case CPU_BLUE:
@@ -697,6 +699,28 @@ initializecpu(void)
        }
        enable_sse();
 
+       if (cpu_vendor_id == CPU_VENDOR_AMD) {
+               switch((cpu_id & 0xFF0000)) {
+               case 0x100000:
+               case 0x120000:
+                       /*
+                        * Errata 721 is the cpu bug found by your's truly
+                        * (Matthew Dillon).  It is a bug where a sequence
+                        * of 5 or more popq's + a retq, under involved
+                        * deep recursion circumstances, can cause the %rsp
+                        * to not be properly updated, almost always
+                        * resulting in a seg-fault soon after.
+                        */
+                       msr = rdmsr(0xc0011029);
+                       if ((msr & 1) == 0) {
+                               kprintf("Errata 721 workaround installed\n");
+                               msr |= 1;
+                               wrmsr(0xc0011029, msr);
+                       }
+                       break;
+               }
+       }
+
        if (cpu_feature2 & CPUID2_VMM)
                vmm_guest = 1;