| Message ID | 20170927151329.70011-16-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Sep 27, 2017 at 10:13:27AM -0500, Brijesh Singh wrote: > KVM guest defines three per-CPU variables (steal-time, apf_reason, and > avic_eio) 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. > > 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> > Acked-by: Tejun Heo <tj@kernel.org> > --- > include/asm-generic/vmlinux.lds.h | 19 +++++++++++++++++++ > include/linux/percpu-defs.h | 15 +++++++++++++++ > 2 files changed, 34 insertions(+) Reviewed-by: Borislav Petkov <bp@suse.de>
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 8acfc1e099e1..2dd54c3e1a8a 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -778,6 +778,24 @@ #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. * * Some archs want to discard exit text/data at runtime rather than @@ -815,6 +833,7 @@ . = ALIGN(cacheline); \ *(.data..percpu) \ *(.data..percpu..shared_aligned) \ + PERCPU_DECRYPTED_SECTION \ VMLINUX_SYMBOL(__per_cpu_end) = .; /** diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h index 8f16299ca068..2d2096ba1cfe 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 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 * noop if __CHECKER__.