svn commit: r291851 - head/sys/x86/x86

[Konstantin Belousov]

Author: kib
Date: Sat Dec  5 08:52:37 2015
New Revision: 291851
URL: https://svnweb.freebsd.org/changeset/base/291851

Log:
  It seems that at least some KVM versions advertise support for EIO
  suppression but the version of the IOAPIC reported is 0x11 and neither
  IOAPIC EOIR nor the Linux trick of temporal reprogramming of the pin
  to edge-trigger mode to issue EOI work.
  
  Disable eoi suppression if KVM is detected.  The mode can still be
  forced with the tunable.
  
  Reported and tested by:	Roman Mamontov <mr.xanto at gmail.com>
  Sponsored by:	The FreeBSD Foundation

Modified:
  head/sys/x86/x86/local_apic.c

Modified: head/sys/x86/x86/local_apic.c
==============================================================================
--- head/sys/x86/x86/local_apic.c	Sat Dec  5 08:46:41 2015	(r291850)
+++ head/sys/x86/x86/local_apic.c	Sat Dec  5 08:52:37 2015	(r291851)
@@ -467,10 +467,20 @@ native_lapic_init(vm_paddr_t addr)
 	 * we by default enable suppression even when system only has
 	 * one IO-APIC, since EOI is broadcasted to all APIC agents,
 	 * including CPUs, otherwise.
+	 *
+	 * It seems that at least some KVM versions report
+	 * EOI_SUPPRESSION bit, but auto-EOI does not work.
 	 */
 	ver = lapic_read32(LAPIC_VERSION);
 	if ((ver & APIC_VER_EOI_SUPPRESSION) != 0) {
 		lapic_eoi_suppression = 1;
+		if (vm_guest == VM_GUEST_VM &&
+		    !strcmp(hv_vendor, "KVMKVMKVM")) {
+			if (bootverbose)
+				printf(
+		       "KVM -- disabling lapic eoi suppression\n");
+			lapic_eoi_suppression = 0;
+		}
 		TUNABLE_INT_FETCH("hw.lapic_eoi_suppression",
 		    &lapic_eoi_suppression);
 	}