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@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxx> Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Tejun Heo <tj@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: linux-arch@xxxxxxxxxxxxxxx Cc: x86@xxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: Tom Lendacky <thomas.lendacky@xxxxxxx> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> --- 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
