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From: Joerg Roedel <joro@8bytes.org>
To: x86@kernel.org
Cc: Joerg Roedel <joro@8bytes.org>, Joerg Roedel <jroedel@suse.de>,
	stable@vger.kernel.org, hpa@zytor.com,
	Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Jiri Slaby <jslaby@suse.cz>,
	Dan Williams <dan.j.williams@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Juergen Gross <jgross@suse.com>,
	Kees Cook <keescook@chromium.org>,
	David Rientjes <rientjes@google.com>,
	Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mike Stunes <mstunes@vmware.com>,
	Sean Christopherson <seanjc@google.com>,
	Martin Radev <martin.b.radev@gmail.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: [RFC PATCH 01/12] kexec: Allow architecture code to opt-out at runtime
Date: Mon,  5 Jul 2021 10:24:32 +0200	[thread overview]
Message-ID: <20210705082443.14721-2-joro@8bytes.org> (raw)
In-Reply-To: <20210705082443.14721-1-joro@8bytes.org>

From: Joerg Roedel <jroedel@suse.de>

Allow a runtime opt-out of kexec support for architecture code in case
the kernel is running in an environment where kexec is not properly
supported yet.

This will be used on x86 when the kernel is running as an SEV-ES
guest. SEV-ES guests need special handling for kexec to hand over all
CPUs to the new kernel. This requires special hypervisor support and
handling code in the guest which is not yet implemented.

Cc: stable@vger.kernel.org # v5.10+
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 include/linux/kexec.h |  2 ++
 kernel/kexec.c        | 14 ++++++++++++++
 kernel/kexec_file.c   |  9 +++++++++
 3 files changed, 25 insertions(+)

diff --git a/include/linux/kexec.h b/include/linux/kexec.h
index 0c994ae37729..400aae677435 100644
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -422,6 +422,8 @@ static inline int kexec_crash_loaded(void) { return 0; }
 #define kexec_in_progress false
 #endif /* CONFIG_KEXEC_CORE */
 
+bool arch_kexec_supported(void);
+
 #endif /* !defined(__ASSEBMLY__) */
 
 #endif /* LINUX_KEXEC_H */
diff --git a/kernel/kexec.c b/kernel/kexec.c
index c82c6c06f051..d03134160458 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -195,11 +195,25 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments,
  * that to happen you need to do that yourself.
  */
 
+bool __weak arch_kexec_supported(void)
+{
+	return true;
+}
+
 static inline int kexec_load_check(unsigned long nr_segments,
 				   unsigned long flags)
 {
 	int result;
 
+	/*
+	 * The architecture may support kexec in general, but the kernel could
+	 * run in an environment where it is not (yet) possible to execute a new
+	 * kernel. Allow the architecture code to opt-out of kexec support when
+	 * it is running in such an environment.
+	 */
+	if (!arch_kexec_supported())
+		return -ENOSYS;
+
 	/* We only trust the superuser with rebooting the system. */
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 33400ff051a8..96d08a512e9c 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -358,6 +358,15 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
 	int ret = 0, i;
 	struct kimage **dest_image, *image;
 
+	/*
+	 * The architecture may support kexec in general, but the kernel could
+	 * run in an environment where it is not (yet) possible to execute a new
+	 * kernel. Allow the architecture code to opt-out of kexec support when
+	 * it is running in such an environment.
+	 */
+	if (!arch_kexec_supported())
+		return -ENOSYS;
+
 	/* We only trust the superuser with rebooting the system. */
 	if (!capable(CAP_SYS_BOOT) || kexec_load_disabled)
 		return -EPERM;
-- 
2.31.1


  reply	other threads:[~2021-07-05  8:26 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-05  8:24 [RFC PATCH 00/12] x86/sev: KEXEC/KDUMP support for SEV-ES guests Joerg Roedel
2021-07-05  8:24 ` Joerg Roedel [this message]
2021-07-05  8:24 ` [RFC PATCH 02/12] x86/kexec/64: Forbid kexec when running as an SEV-ES guest Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 03/12] x86/sev: Save and print negotiated GHCB protocol version Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 04/12] x86/sev: Do not hardcode " Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 05/12] x86/sev: Use GHCB protocol version 2 if supported Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 06/12] x86/sev: Cache AP Jump Table Address Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 07/12] x86/sev: Setup code to park APs in the AP Jump Table Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 08/12] x86/sev: Park APs on AP Jump Table with GHCB protocol version 2 Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 09/12] x86/sev: Use AP Jump Table blob to stop CPU Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 10/12] x86/sev: Add MMIO handling support to boot/compressed/ code Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 11/12] x86/sev: Handle CLFLUSH MMIO events Joerg Roedel
2021-07-05  8:24 ` [RFC PATCH 12/12] x86/sev: Support kexec under SEV-ES with AP Jump Table blob Joerg Roedel

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