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percpu: Introduce DEFINE_PER_CPU_DECRYPTED

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KVM guest defines three per-CPU variables (steal-time, apf_reason, and
kvm_pic_eoi) which are shared between a guest and a hypervisor.

When SEV is active, memory is encrypted with a guest-specific key, and if
the guest OS wants to share the memory region with the hypervisor then it
must clear the C-bit (i.e set decrypted) before sharing it.

DEFINE_PER_CPU_DECRYPTED can be used to define the per-CPU variables
which will be shared between a guest and a hypervisor.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Borislav Petkov <bp@suse.de>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: linux-arch@vger.kernel.org
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: kvm@vger.kernel.org
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Lameter <cl@linux.com>
Link: https://lkml.kernel.org/r/20171020143059.3291-16-brijesh.singh@amd.com
This commit is contained in:
Brijesh Singh 2017-10-20 09:30:57 -05:00 committed by Thomas Gleixner
parent dfaaec9033
commit ac26963a11
2 changed files with 34 additions and 0 deletions
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19
include/asm-generic/vmlinux.lds.h
View File

@ -777,6 +777,24 @@
#define INIT_RAM_FS
#endif
/*
* Memory encryption operates on a page basis. Since we need to clear
* the memory encryption mask for this section, it needs to be aligned
* on a page boundary and be a page-size multiple in length.
*
* Note: We use a separate section so that only this section gets
* decrypted to avoid exposing more than we wish.
*/
#ifdef CONFIG_AMD_MEM_ENCRYPT
#define PERCPU_DECRYPTED_SECTION \
. = ALIGN(PAGE_SIZE); \
*(.data..percpu..decrypted) \
. = ALIGN(PAGE_SIZE);
#else
#define PERCPU_DECRYPTED_SECTION
#endif
/*
* Default discarded sections.
*
@ -815,6 +833,7 @@
. = ALIGN(cacheline); \
*(.data..percpu) \
*(.data..percpu..shared_aligned) \
PERCPU_DECRYPTED_SECTION \
VMLINUX_SYMBOL(__per_cpu_end) = .;
/**

15
include/linux/percpu-defs.h
View File

@ -172,6 +172,21 @@
#define DEFINE_PER_CPU_READ_MOSTLY(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "..read_mostly")
/*
* Declaration/definition used for per-CPU variables that should be accessed
* as decrypted when memory encryption is enabled in the guest.
*/
#if defined(CONFIG_VIRTUALIZATION) && defined(CONFIG_AMD_MEM_ENCRYPT)
#define DECLARE_PER_CPU_DECRYPTED(type, name) \
DECLARE_PER_CPU_SECTION(type, name, "..decrypted")
#define DEFINE_PER_CPU_DECRYPTED(type, name) \
DEFINE_PER_CPU_SECTION(type, name, "..decrypted")
#else
#define DEFINE_PER_CPU_DECRYPTED(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