linux-kernel - Re: [PATCH v2] entry/kvm: Make vCPU tasks exit to userspace when a livepatch is pending

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Date:   Wed, 04 May 2022 14:44:34 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Seth Forshee <sforshee@...italocean.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v2] entry/kvm: Make vCPU tasks exit to userspace when a
 livepatch is pending

On Tue, May 03 2022 at 12:49, Seth Forshee wrote:
> diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
> index 6813171afccb..bf79e4cbb5a2 100644
> --- a/include/linux/entry-kvm.h
> +++ b/include/linux/entry-kvm.h
> @@ -17,8 +17,8 @@
>  #endif
>  
>  #define XFER_TO_GUEST_MODE_WORK						\
> -	(_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL |	\
> -	 _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK)
> +	(_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_PATCH_PENDING |	\
> +	 _TIF_NOTIFY_SIGNAL | _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK)

as the 0-day robot has demonstrated already, this cannot compile on
architectures which do not provide _TIF_PATCH_PENDING...

Something like the below is required.

Thanks,

        tglx
---
--- a/include/linux/entry-common.h
+++ b/include/linux/entry-common.h
@@ -3,6 +3,7 @@
 #define __LINUX_ENTRYCOMMON_H
 
 #include <linux/static_call_types.h>
+#include <linux/entry-defs.h>
 #include <linux/ptrace.h>
 #include <linux/syscalls.h>
 #include <linux/seccomp.h>
@@ -11,18 +12,6 @@
 #include <asm/entry-common.h>
 
 /*
- * Define dummy _TIF work flags if not defined by the architecture or for
- * disabled functionality.
- */
-#ifndef _TIF_PATCH_PENDING
-# define _TIF_PATCH_PENDING		(0)
-#endif
-
-#ifndef _TIF_UPROBE
-# define _TIF_UPROBE			(0)
-#endif
-
-/*
  * SYSCALL_WORK flags handled in syscall_enter_from_user_mode()
  */
 #ifndef ARCH_SYSCALL_WORK_ENTER
--- /dev/null
+++ b/include/linux/entry-defs.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_ENTRYDEFS_H
+#define __LINUX_ENTRYDEFS_H
+
+#include <linux/thread_info.h>
+
+/*
+ * Define dummy _TIF work flags if not defined by the architecture or for
+ * disabled functionality.
+ */
+#ifndef _TIF_PATCH_PENDING
+# define _TIF_PATCH_PENDING		(0)
+#endif
+
+#ifndef _TIF_UPROBE
+# define _TIF_UPROBE			(0)
+#endif
+
+#endif
--- a/include/linux/entry-kvm.h
+++ b/include/linux/entry-kvm.h
@@ -4,6 +4,7 @@
 
 #include <linux/static_call_types.h>
 #include <linux/resume_user_mode.h>
+#include <linux/entry-defs.h>
 #include <linux/syscalls.h>
 #include <linux/seccomp.h>
 #include <linux/sched.h>