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authorBoris Ostrovsky <boris.ostrovsky@oracle.com>2017-04-24 15:04:53 -0400
committerJuergen Gross <jgross@suse.com>2017-05-02 11:18:05 +0200
commit84d582d236dc1f9085e741affc72e9ba061a67c2 (patch)
tree7d012e4f1739b44c0bb5373a091a6f195c057d82 /arch/x86/xen/time.c
parent5f6a1614fab801834e32b420b60acdc27acfcdec (diff)
xen: Revert commits da72ff5bfcb0 and 72a9b186292d
Recent discussion (http://marc.info/?l=xen-devel&m=149192184523741) established that commit 72a9b186292d ("xen: Remove event channel notification through Xen PCI platform device") (and thus commit da72ff5bfcb0 ("partially revert "xen: Remove event channel notification through Xen PCI platform device"")) are unnecessary and, in fact, prevent HVM guests from booting on Xen releases prior to 4.0 Therefore we revert both of those commits. The summary of that discussion is below: Here is the brief summary of the current situation: Before the offending commit (72a9b186292): 1) INTx does not work because of the reset_watches path. 2) The reset_watches path is only taken if you have Xen > 4.0 3) The Linux Kernel by default will use vector inject if the hypervisor support. So even INTx does not work no body running the kernel with Xen > 4.0 would notice. Unless he explicitly disabled this feature either in the kernel or in Xen (and this can only be disabled by modifying the code, not user-supported way to do it). After the offending commit (+ partial revert): 1) INTx is no longer support for HVM (only for PV guests). 2) Any HVM guest The kernel will not boot on Xen < 4.0 which does not have vector injection support. Since the only other mode supported is INTx which. So based on this summary, I think before commit (72a9b186292) we were in much better position from a user point of view. Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> Reviewed-by: Juergen Gross <jgross@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com>
Diffstat (limited to 'arch/x86/xen/time.c')
-rw-r--r--arch/x86/xen/time.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 7a3089285c59..090c7eb4dca9 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -436,6 +436,14 @@ static void xen_hvm_setup_cpu_clockevents(void)
void __init xen_hvm_init_time_ops(void)
{
+ /*
+ * vector callback is needed otherwise we cannot receive interrupts
+ * on cpu > 0 and at this point we don't know how many cpus are
+ * available.
+ */
+ if (!xen_have_vector_callback)
+ return;
+
if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
printk(KERN_INFO "Xen doesn't support pvclock on HVM,"
"disable pv timer\n");