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Subject[Part1 PATCH v4 15/17] percpu: introduce DEFINE_PER_CPU_UNENCRYPTED
Date
When SEV is active, memory is encrypted with guest-specific key, and if
guest OS wants to share the memory region with hypervisor then it must
clear the C-bit (i.e set unencrypted) before sharing it.

DEFINE_PER_CPU_UNENCRYPTED can be used to define the per-cpu variables
which will be shared between guest and hypervisor. Currently, KVM defines
three variables (steal-time, apf_reason, and avic_eio) which are shared
with hypervisor.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
include/asm-generic/vmlinux.lds.h | 11 +++++++++++
include/linux/percpu-defs.h | 15 +++++++++++++++
2 files changed, 26 insertions(+)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 8acfc1e099e1..363858f43cbc 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -777,6 +777,16 @@
#define INIT_RAM_FS
#endif

+#ifdef CONFIG_AMD_MEM_ENCRYPT
+#define PERCPU_UNENCRYPTED_SECTION \
+ . = ALIGN(PAGE_SIZE); \
+ *(.data..percpu..unencrypted) \
+ . = ALIGN(PAGE_SIZE);
+#else
+#define PERCPU_UNENCRYPTED_SECTION
+#endif
+
+
/*
* Default discarded sections.
*
@@ -815,6 +825,7 @@
. = ALIGN(cacheline); \
*(.data..percpu) \
*(.data..percpu..shared_aligned) \
+ PERCPU_UNENCRYPTED_SECTION \
VMLINUX_SYMBOL(__per_cpu_end) = .;

/**
diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
index 8f16299ca068..b2b99ad4b31d 100644
--- a/include/linux/percpu-defs.h
+++ b/include/linux/percpu-defs.h
@@ -173,6 +173,21 @@
DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")

/*
+ * Declaration/definition used for per-CPU variables that should be accessed
+ * as unencrypted when memory encryption is enabled in the guest.
+ */
+#if defined(CONFIG_VIRTUALIZATION) && defined(CONFIG_AMD_MEM_ENCRYPT)
+
+#define DECLARE_PER_CPU_UNENCRYPTED(type, name) \
+ DECLARE_PER_CPU_SECTION(type, name, "..unencrypted")
+
+#define DEFINE_PER_CPU_UNENCRYPTED(type, name) \
+ DEFINE_PER_CPU_SECTION(type, name, "..unencrypted")
+#else
+#define DEFINE_PER_CPU_UNENCRYPTED(type, name) DEFINE_PER_CPU(type, name)
+#endif
+
+/*
* Intermodule exports for per-CPU variables. sparse forgets about
* address space across EXPORT_SYMBOL(), change EXPORT_SYMBOL() to
* noop if __CHECKER__.
--
2.9.5
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