[xen master] xen/x86: introduce MCE_NONFATAL

[patchbot@xxxxxxx]

commit 4c1cd02acb563d9a8a0485e795760e0bb149fe43
Author:     Stefano Stabellini <stefano.stabellini@xxxxxxx>
AuthorDate: Tue Jul 8 11:32:38 2025 -0700
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxx>
CommitDate: Wed Jul 9 18:21:27 2025 -0700

    xen/x86: introduce MCE_NONFATAL
    
    Today, checking for non-fatal MCE errors on AMD is very invasive: it
    involves a periodic timer interrupting the physical CPU execution at
    regular intervals. Moreover, when the timer fires, the handler sends an
    IPI to all physical CPUs.
    
    Both these actions are disruptive in terms of latency and deterministic
    execution times for real-time workloads. They might miss a deadline due
    to one of these IPIs. Make it possible to disable non-fatal MCE errors
    checking with a new Kconfig option (MCE_NONFATAL).
    
    Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
    Reviewed-by: Alejandro Vallejo <alejandro.garciavallejo@xxxxxxx>
    Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/Kconfig             | 14 ++++++++++++++
 xen/arch/x86/cpu/mcheck/Makefile |  6 +++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/Kconfig b/xen/arch/x86/Kconfig
index 752d5141bb..9ec0fb0bed 100644
--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -248,6 +248,20 @@ config X2APIC_MIXED
 
 endchoice
 
+config MCE_NONFATAL
+       bool "Check for non-fatal MCEs" if EXPERT
+       default y
+       help
+         Check for non-fatal MCE errors.
+       
+         When this option is on (default), Xen regularly checks for
+         non-fatal MCEs potentially occurring on all physical CPUs. The
+         checking is done via timers and IPI interrupts, which is
+         acceptable in most configurations, but not for real-time.
+       
+         Turn this option off if you plan on deploying real-time workloads
+         on Xen.
+
 config GUEST
        bool
 
diff --git a/xen/arch/x86/cpu/mcheck/Makefile b/xen/arch/x86/cpu/mcheck/Makefile
index e6cb4dd503..c70b441888 100644
--- a/xen/arch/x86/cpu/mcheck/Makefile
+++ b/xen/arch/x86/cpu/mcheck/Makefile
@@ -1,12 +1,12 @@
-obj-$(CONFIG_AMD) += amd_nonfatal.o
+obj-$(filter $(CONFIG_AMD),$(CONFIG_MCE_NONFATAL)) += amd_nonfatal.o
 obj-$(CONFIG_AMD) += mce_amd.o
 obj-y += mcaction.o
 obj-y += barrier.o
-obj-$(CONFIG_INTEL) += intel-nonfatal.o
+obj-$(filter $(CONFIG_INTEL),$(CONFIG_MCE_NONFATAL)) += intel-nonfatal.o
 obj-y += mctelem.o
 obj-y += mce.o
 obj-y += mce-apei.o
 obj-$(CONFIG_INTEL) += mce_intel.o
-obj-y += non-fatal.o
+obj-$(CONFIG_MCE_NONFATAL) += non-fatal.o
 obj-y += util.o
 obj-y += vmce.o
--
generated by git-patchbot for /home/xen/git/xen.git#master