[tip:x86/asm] x86/io: Unroll string I/O when SEV is active

tip-bot for Tom Lendacky
2017-11-07T14:51:18Z

Commit-ID: 606b21d4a6498c23632a4693c81b7b24feedd038
Gitweb: https://git.kernel.org/tip/606b21d4a6498c23632a4693c81b7b24feedd038
Author: Tom Lendacky <thomas.lendacky@amd.com>
AuthorDate: Fri, 20 Oct 2017 09:30:55 -0500
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Tue, 7 Nov 2017 15:35:59 +0100

x86/io: Unroll string I/O when SEV is active

Secure Encrypted Virtualization (SEV) does not support string I/O, so
unroll the string I/O operation into a loop operating on one element at
a time.

[ tglx: Gave the static key a real name instead of the obscure __sev ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Tested-by: Borislav Petkov <bp@suse.de>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: kvm@vger.kernel.org
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Borislav Petkov <bp@alien8.de>
Link: https://lkml.kernel.org/r/20171020143059.3291-14-brijesh.singh@amd.com

---
arch/x86/include/asm/io.h | 43 +++++++++++++++++++++++++++++++++++++++----
arch/x86/mm/mem_encrypt.c | 8 ++++++++
2 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index 11398d5..93ae8ae 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -266,6 +266,21 @@ static inline void slow_down_io(void)

#endif

+#ifdef CONFIG_AMD_MEM_ENCRYPT
+#include <linux/jump_label.h>
+
+extern struct static_key_false sev_enable_key;
+static inline bool sev_key_active(void)
+{
+ return static_branch_unlikely(&sev_enable_key);
+}
+
+#else /* !CONFIG_AMD_MEM_ENCRYPT */
+
+static inline bool sev_key_active(void) { return false; }
+
+#endif /* CONFIG_AMD_MEM_ENCRYPT */
+
#define BUILDIO(bwl, bw, type) \
static inline void out##bwl(unsigned type value, int port) \
{ \
@@ -296,14 +311,34 @@ static inline unsigned type in##bwl##_p(int port) \
\
static inline void outs##bwl(int port, const void *addr, unsigned long count) \
{ \
- asm volatile("rep; outs" #bwl \
- : "+S"(addr), "+c"(count) : "d"(port) : "memory"); \
+ if (sev_key_active()) { \
+ unsigned type *value = (unsigned type *)addr; \
+ while (count) { \
+ out##bwl(*value, port); \
+ value++; \
+ count--; \
+ } \
+ } else { \
+ asm volatile("rep; outs" #bwl \
+ : "+S"(addr), "+c"(count) \
+ : "d"(port) : "memory"); \
+ } \
} \
\
static inline void ins##bwl(int port, void *addr, unsigned long count) \
{ \
- asm volatile("rep; ins" #bwl \
- : "+D"(addr), "+c"(count) : "d"(port) : "memory"); \
+ if (sev_key_active()) { \
+ unsigned type *value = (unsigned type *)addr; \
+ while (count) { \
+ *value = in##bwl(port); \
+ value++; \
+ count--; \
+ } \
+ } else { \
+ asm volatile("rep; ins" #bwl \
+ : "+D"(addr), "+c"(count) \
+ : "d"(port) : "memory"); \
+ } \
}

BUILDIO(b, b, char)
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index fd9c7bb..d29b783 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -41,6 +41,8 @@ static char sme_cmdline_off[] __initdata = "off";
*/
u64 sme_me_mask __section(.data) = 0;
EXPORT_SYMBOL_GPL(sme_me_mask);
+DEFINE_STATIC_KEY_FALSE(sev_enable_key);
+EXPORT_SYMBOL_GPL(sev_enable_key);

static bool sev_enabled __section(.data);

@@ -313,6 +315,12 @@ void __init mem_encrypt_init(void)
if (sev_active())
dma_ops = &sev_dma_ops;

+ /*
+ * With SEV, we need to unroll the rep string I/O instructions.
+ */
+ if (sev_active())
+ static_branch_enable(&sev_enable_key);
+
pr_info("AMD %s active\n",
sev_active() ? "Secure Encrypted Virtualization (SEV)"
: "Secure Memory Encryption (SME)");