[Patch v3 4/4] x86/platform/UV: use efi_runtime_lock to serialise BIOS calls

[Hedi Berriche]

Calls into UV firmware must be protected against concurrency, expose the
efi_runtime_lock to the UV platform, and use it to serialise UV BIOS calls.

Cc: Russ Anderson <r...@hpe.com>
Cc: Mike Travis <mike.tra...@hpe.com>
Cc: Dimitri Sivanich <sivan...@hpe.com>
Cc: Steve Wahl <steve.w...@hpe.com>
Cc: sta...@vger.kernel.org # v4.9+
Signed-off-by: Hedi Berriche <hedi.berri...@hpe.com>
---
 arch/x86/include/asm/uv/bios.h          |  8 +++++++-
 arch/x86/platform/uv/bios_uv.c          | 23 +++++++++++++++++++++--
 drivers/firmware/efi/runtime-wrappers.c |  7 +++++++
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/uv/bios.h b/arch/x86/include/asm/uv/bios.h
index 8c6ac271b5b3..8cfccc3cbbf4 100644
--- a/arch/x86/include/asm/uv/bios.h
+++ b/arch/x86/include/asm/uv/bios.h
@@ -48,7 +48,8 @@ enum {
        BIOS_STATUS_SUCCESS             =  0,
        BIOS_STATUS_UNIMPLEMENTED       = -ENOSYS,
        BIOS_STATUS_EINVAL              = -EINVAL,
-       BIOS_STATUS_UNAVAIL             = -EBUSY
+       BIOS_STATUS_UNAVAIL             = -EBUSY,
+       BIOS_STATUS_ABORT               = -EINTR,
 };
 
 /* Address map parameters */
@@ -162,4 +163,9 @@ extern long system_serial_number;
 
 extern struct kobject *sgi_uv_kobj;    /* /sys/firmware/sgi_uv */
 
+/*
+ * EFI runtime lock; cf. firmware/efi/runtime-wrappers.c for details
+ */
+extern struct semaphore __efi_uv_runtime_lock;
+
 #endif /* _ASM_X86_UV_BIOS_H */
diff --git a/arch/x86/platform/uv/bios_uv.c b/arch/x86/platform/uv/bios_uv.c
index 38a2e3431fc6..ef60d789c76e 100644
--- a/arch/x86/platform/uv/bios_uv.c
+++ b/arch/x86/platform/uv/bios_uv.c
@@ -29,7 +29,8 @@
 
 struct uv_systab *uv_systab;
 
-s64 uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, u64 a4, u64 
a5)
+static s64 __uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3,
+                       u64 a4, u64 a5)
 {
        struct uv_systab *tab = uv_systab;
        s64 ret;
@@ -51,6 +52,19 @@ s64 uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 
a3, u64 a4, u64 a5)
 
        return ret;
 }
+
+s64 uv_bios_call(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3, u64 a4, u64 
a5)
+{
+       s64 ret;
+
+       if (down_interruptible(&__efi_uv_runtime_lock))
+               return BIOS_STATUS_ABORT;
+
+       ret = __uv_bios_call(which, a1, a2, a3, a4, a5);
+       up(&__efi_uv_runtime_lock);
+
+       return ret;
+}
 EXPORT_SYMBOL_GPL(uv_bios_call);
 
 s64 uv_bios_call_irqsave(enum uv_bios_cmd which, u64 a1, u64 a2, u64 a3,
@@ -59,10 +73,15 @@ s64 uv_bios_call_irqsave(enum uv_bios_cmd which, u64 a1, 
u64 a2, u64 a3,
        unsigned long bios_flags;
        s64 ret;
 
+       if (down_interruptible(&__efi_uv_runtime_lock))
+               return BIOS_STATUS_ABORT;
+
        local_irq_save(bios_flags);
-       ret = uv_bios_call(which, a1, a2, a3, a4, a5);
+       ret = __uv_bios_call(which, a1, a2, a3, a4, a5);
        local_irq_restore(bios_flags);
 
+       up(&__efi_uv_runtime_lock);
+
        return ret;
 }
 
diff --git a/drivers/firmware/efi/runtime-wrappers.c 
b/drivers/firmware/efi/runtime-wrappers.c
index 8903b9ccfc2b..e2abfdb5cee6 100644
--- a/drivers/firmware/efi/runtime-wrappers.c
+++ b/drivers/firmware/efi/runtime-wrappers.c
@@ -146,6 +146,13 @@ void efi_call_virt_check_flags(unsigned long flags, const 
char *call)
  */
 static DEFINE_SEMAPHORE(efi_runtime_lock);
 
+/*
+ * Expose the EFI runtime lock to the UV platform
+ */
+#ifdef CONFIG_X86_UV
+extern struct semaphore __efi_uv_runtime_lock __alias(efi_runtime_lock);
+#endif
+
 /*
  * Calls the appropriate efi_runtime_service() with the appropriate
  * arguments.
-- 
2.20.1