x86/setup: Do not reserve a crash kernel region if booted on Xen PV

Petr Tesarik · KAGA-KOKO · commit 3db3eb285259 · 2018-04-27T17:06:28.000+02:00
Xen PV domains cannot shut down and start a crash kernel. Instead, the crashing kernel makes a SCHEDOP_shutdown hypercall with the reason code SHUTDOWN_crash, cf. xen_crash_shutdown() machine op in arch/x86/xen/enlighten_pv.c. A crash kernel reservation is merely a waste of RAM in this case. It may also confuse users of kexec_load(2) and/or kexec_file_load(2). When flags include KEXEC_ON_CRASH or KEXEC_FILE_ON_CRASH, respectively, these syscalls return success, which is technically correct, but the crash kexec image will never be actually used. Signed-off-by: Petr Tesarik <ptesarik@suse.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Juergen Gross <jgross@suse.com> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Dou Liyang <douly.fnst@cn.fujitsu.com> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: xen-devel@lists.xenproject.org Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Borislav Petkov <bp@suse.de> Cc: Jean Delvare <jdelvare@suse.de> Link: https://lkml.kernel.org/r/20180425120835.23cef60c@ezekiel.suse.cz
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
@@ -50,6 +50,7 @@
 #include <linux/init_ohci1394_dma.h>
 #include <linux/kvm_para.h>
 #include <linux/dma-contiguous.h>
+#include <xen/xen.h>
 
 #include <linux/errno.h>
 #include <linux/kernel.h>
@@ -534,6 +535,11 @@ static void __init reserve_crashkernel(void)
 		high = true;
 	}
 
+	if (xen_pv_domain()) {
+		pr_info("Ignoring crashkernel for a Xen PV domain\n");
+		return;
+	}
+
 	/* 0 means: find the address automatically */
 	if (crash_base <= 0) {
 		/*
