[PATCH 5.10 056/199] x86/xen: Add xen_no_vector_callback option to test PCI INTX delivery

Greg Kroah-Hartman
2021-01-25T19:11:35Z

From: David Woodhouse <dwmw@amazon.co.uk>

[ Upstream commit b36b0fe96af13460278bf9b173beced1bd15f85d ]

It's useful to be able to test non-vector event channel delivery, to make
sure Linux will work properly on older Xen which doesn't have it.

It's also useful for those working on Xen and Xen-compatible hypervisors,
because there are guest kernels still in active use which use PCI INTX
even when vector delivery is available.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20210106153958.584169-4-dwmw2@infradead.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
Documentation/admin-guide/kernel-parameters.txt | 4 ++++
arch/x86/xen/enlighten_hvm.c | 11 ++++++++++-
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f6a1513dfb76c..26bfe7ae711b8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5965,6 +5965,10 @@
This option is obsoleted by the "nopv" option, which
has equivalent effect for XEN platform.

+ xen_no_vector_callback
+ [KNL,X86,XEN] Disable the vector callback for Xen
+ event channel interrupts.
+
xen_scrub_pages= [XEN]
Boolean option to control scrubbing pages before giving them back
to Xen, for use by other domains. Can be also changed at runtime
diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index 9e87ab010c82b..ec50b7423a4c8 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -188,6 +188,8 @@ static int xen_cpu_dead_hvm(unsigned int cpu)
return 0;
}

+static bool no_vector_callback __initdata;
+
static void __init xen_hvm_guest_init(void)
{
if (xen_pv_domain())
@@ -207,7 +209,7 @@ static void __init xen_hvm_guest_init(void)

xen_panic_handler_init();

- if (xen_feature(XENFEAT_hvm_callback_vector))
+ if (!no_vector_callback && xen_feature(XENFEAT_hvm_callback_vector))
xen_have_vector_callback = 1;

xen_hvm_smp_init();
@@ -233,6 +235,13 @@ static __init int xen_parse_nopv(char *arg)
}
early_param("xen_nopv", xen_parse_nopv);

+static __init int xen_parse_no_vector_callback(char *arg)
+{
+ no_vector_callback = true;
+ return 0;
+}
+early_param("xen_no_vector_callback", xen_parse_no_vector_callback);
+
bool __init xen_hvm_need_lapic(void)
{
if (xen_pv_domain())
--
2.27.0