Move FPEXC32_EL2 to FP Context
The FPEXC32_EL2 register controls SIMD and FP functionality when the
lower ELs are executing in AArch32 mode. It is architecturally mapped
to AArch32 system register FPEXC.
This patch removes FPEXC32_EL2 register from the System Register context
and adds it to the floating-point context. EL3 only saves / restores the
floating-point context if the build option CTX_INCLUDE_FPREGS is set to 1.
The rationale for this change is that if the Secure world is using FP
functionality and EL3 is not managing the FP context, then the Secure
world will save / restore the appropriate FP registers.
NOTE - this is a break in behaviour in the unlikely case that
CTX_INCLUDE_FPREGS is set to 0 and the platform contains an AArch32
Secure Payload that modifies FPEXC, but does not save and restore
this register
Change-Id: Iab80abcbfe302752d52b323b4abcc334b585c184
Signed-off-by: David Cunado <david.cunado@arm.com>
diff --git a/lib/el3_runtime/aarch64/context.S b/lib/el3_runtime/aarch64/context.S
index db16a9f..143da95 100644
--- a/lib/el3_runtime/aarch64/context.S
+++ b/lib/el3_runtime/aarch64/context.S
@@ -90,9 +90,6 @@
mrs x15, dacr32_el2
mrs x16, ifsr32_el2
stp x15, x16, [x0, #CTX_DACR32_EL2]
-
- mrs x17, fpexc32_el2
- str x17, [x0, #CTX_FP_FPEXC32_EL2]
#endif
/* Save NS timer registers if the build has instructed so */
@@ -212,9 +209,6 @@
ldp x15, x16, [x0, #CTX_DACR32_EL2]
msr dacr32_el2, x15
msr ifsr32_el2, x16
-
- ldr x17, [x0, #CTX_FP_FPEXC32_EL2]
- msr fpexc32_el2, x17
#endif
/* Restore NS timer registers if the build has instructed so */
#if NS_TIMER_SWITCH
@@ -275,6 +269,10 @@
mrs x10, fpcr
str x10, [x0, #CTX_FP_FPCR]
+#if CTX_INCLUDE_AARCH32_REGS
+ mrs x11, fpexc32_el2
+ str x11, [x0, #CTX_FP_FPEXC32_EL2]
+#endif
ret
endfunc fpregs_context_save
@@ -318,6 +316,10 @@
ldr x10, [x0, #CTX_FP_FPCR]
msr fpcr, x10
+#if CTX_INCLUDE_AARCH32_REGS
+ ldr x11, [x0, #CTX_FP_FPEXC32_EL2]
+ msr fpexc32_el2, x11
+#endif
/*
* No explict ISB required here as ERET to
* switch to secure EL1 or non-secure world