From bebcf27f1c75f48cc129e8608cba113d0db32ef8 Mon Sep 17 00:00:00 2001
From: Mark Brown <broonie@kernel.org>
Date: Wed, 20 Apr 2022 18:14:32 +0100
Subject: [PATCH] feat(sve): support full SVE vector length

Currently the SVE code hard codes a maximum vector length of 512 bits
when configuring SVE rather than the architecture supported maximum.
While this is fine for current physical implementations the architecture
allows for vector lengths up to 2048 bits and emulated implementations
generally allow any length up to this maximum.

Since there may be system specific reasons to limit the maximum vector
length make the limit configurable, defaulting to the architecture
maximum. The default should be suitable for most implementations since
the hardware will limit the actual vector length selected to what is
physically supported in the system.

Signed-off-by: Mark Brown <broonie@kernel.org>
Change-Id: I22c32c98a81c0cf9562411189d8a610a5b61ca12
---
 Makefile                               |  3 +++
 docs/getting_started/build-options.rst |  8 ++++++++
 lib/extensions/sve/sve.c               | 11 ++++++++---
 make_helpers/defaults.mk               |  3 +++
 4 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/Makefile b/Makefile
index ee5e2e7a8..5916963b5 100644
--- a/Makefile
+++ b/Makefile
@@ -399,6 +399,8 @@ TF_CFLAGS		+=	$(CPPFLAGS) $(TF_CFLAGS_$(ARCH))		\
 				-ffreestanding -fno-builtin -fno-common		\
 				-Os -std=gnu99
 
+$(eval $(call add_define,SVE_VECTOR_LEN))
+
 ifeq (${SANITIZE_UB},on)
 TF_CFLAGS		+=	-fsanitize=undefined -fno-sanitize-recover
 endif
@@ -1085,6 +1087,7 @@ $(eval $(call assert_numerics,\
         RAS_EXTENSION \
         TWED_DELAY \
         ENABLE_FEAT_TWED \
+        SVE_VECTOR_LEN \
 )))
 
 ifdef KEY_SIZE
diff --git a/docs/getting_started/build-options.rst b/docs/getting_started/build-options.rst
index 26d545805..b4d340700 100644
--- a/docs/getting_started/build-options.rst
+++ b/docs/getting_started/build-options.rst
@@ -834,6 +834,14 @@ Common build options
    to mask these events. Platforms that enable FIQ handling in SP_MIN shall
    implement the api ``sp_min_plat_fiq_handler()``. The default value is 0.
 
+-  ``SVE_VECTOR_LEN``: SVE vector length to configure in ZCR_EL3.
+   Platforms can configure this if they need to lower the hardware
+   limit, for example due to asymmetric configuration or limitations of
+   software run at lower ELs. The default is the architectural maximum
+   of 2048 which should be suitable for most configurations, the
+   hardware will limit the effective VL to the maximum physically supported
+   VL.
+
 -  ``TRUSTED_BOARD_BOOT``: Boolean flag to include support for the Trusted Board
    Boot feature. When set to '1', BL1 and BL2 images include support to load
    and verify the certificates and images in a FIP, and BL1 includes support
diff --git a/lib/extensions/sve/sve.c b/lib/extensions/sve/sve.c
index aa8904b9b..f7dcc767a 100644
--- a/lib/extensions/sve/sve.c
+++ b/lib/extensions/sve/sve.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -8,9 +8,14 @@
 
 #include <arch.h>
 #include <arch_helpers.h>
+#include <lib/cassert.h>
 #include <lib/el3_runtime/pubsub.h>
 #include <lib/extensions/sve.h>
 
+CASSERT(SVE_VECTOR_LEN <= 2048, assert_sve_vl_too_long);
+CASSERT(SVE_VECTOR_LEN >= 128, assert_sve_vl_too_short);
+CASSERT((SVE_VECTOR_LEN % 128) == 0, assert_sve_vl_granule);
+
 /*
  * Converts SVE vector size restriction in bytes to LEN according to ZCR_EL3 documentation.
  * VECTOR_SIZE = (LEN+1) * 128
@@ -39,9 +44,9 @@ void sve_enable(cpu_context_t *context)
 	cptr_el3 = (cptr_el3 | CPTR_EZ_BIT) & ~(TFP_BIT);
 	write_ctx_reg(get_el3state_ctx(context), CTX_CPTR_EL3, cptr_el3);
 
-	/* Restrict maximum SVE vector length (SVE_VECTOR_LENGTH+1) * 128. */
+	/* Restrict maximum SVE vector length (SVE_VECTOR_LEN+1) * 128. */
 	write_ctx_reg(get_el3state_ctx(context), CTX_ZCR_EL3,
-		(ZCR_EL3_LEN_MASK & CONVERT_SVE_LENGTH(512)));
+		(ZCR_EL3_LEN_MASK & CONVERT_SVE_LENGTH(SVE_VECTOR_LEN)));
 }
 
 void sve_disable(cpu_context_t *context)
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index fab6bf6da..37f6fa9aa 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -373,6 +373,9 @@ ifeq (${ARCH},aarch32)
 endif
 ENABLE_SVE_FOR_SWD		:= 0
 
+# Default SVE vector length to maximum architected value
+SVE_VECTOR_LEN			:= 2048
+
 # SME defaults to disabled
 ENABLE_SME_FOR_NS		:= 0
 ENABLE_SME_FOR_SWD		:= 0