Revert "arm64: smccc: Remove broken support for SMCCCv1.3 SVE discard hint"

This reverts commit bfcaffd4cc which is
commit 8c462d56487e3abdbf8a61cedfe7c795a54f4a78 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I8936edc25779838c941ebaf55f267f386d876403
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

arch/arm64/kernel/smccc-call.S

@@ -7,19 +7,48 @@
 
 #include <asm/asm-offsets.h>
 #include <asm/assembler.h>
+#include <asm/thread_info.h>
+
+/*
+ * If we have SMCCC v1.3 and (as is likely) no SVE state in
+ * the registers then set the SMCCC hint bit to say there's no
+ * need to preserve it.  Do this by directly adjusting the SMCCC
+ * function value which is already stored in x0 ready to be called.
+ */
+SYM_FUNC_START(__arm_smccc_sve_check)
+
+	ldr_l	x16, smccc_has_sve_hint
+	cbz	x16, 2f
+
+	get_current_task x16
+	ldr	x16, [x16, #TSK_TI_FLAGS]
+	tbnz	x16, #TIF_FOREIGN_FPSTATE, 1f	// Any live FP state?
+	tbnz	x16, #TIF_SVE, 2f		// Does that state include SVE?
+
+1:	orr	x0, x0, ARM_SMCCC_1_3_SVE_HINT
+
+2:	ret
+SYM_FUNC_END(__arm_smccc_sve_check)
+EXPORT_SYMBOL(__arm_smccc_sve_check)
 
 	.macro SMCCC instr
+	stp     x29, x30, [sp, #-16]!
+	mov	x29, sp
+alternative_if ARM64_SVE
+	bl	__arm_smccc_sve_check
+alternative_else_nop_endif
 	\instr	#0
-	ldr	x4, [sp]
+	ldr	x4, [sp, #16]
 	stp	x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
 	stp	x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS]
-	ldr	x4, [sp, #8]
+	ldr	x4, [sp, #24]
 	cbz	x4, 1f /* no quirk structure */
 	ldr	x9, [x4, #ARM_SMCCC_QUIRK_ID_OFFS]
 	cmp	x9, #ARM_SMCCC_QUIRK_QCOM_A6
 	b.ne	1f
 	str	x6, [x4, ARM_SMCCC_QUIRK_STATE_OFFS]
-1:	ret
+1:	ldp     x29, x30, [sp], #16
+	ret
 	.endm
 
 /*

drivers/firmware/smccc/smccc.c

@@ -16,6 +16,7 @@ static u32 smccc_version = ARM_SMCCC_VERSION_1_0;
 static enum arm_smccc_conduit smccc_conduit = SMCCC_CONDUIT_NONE;
 
 bool __ro_after_init smccc_trng_available = false;
+u64 __ro_after_init smccc_has_sve_hint = false;
 
 void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit)
 {
@@ -23,6 +24,9 @@ void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit)
 	smccc_conduit = conduit;
 
 	smccc_trng_available = smccc_probe_trng();
+	if (IS_ENABLED(CONFIG_ARM64_SVE) &&
+	    smccc_version >= ARM_SMCCC_VERSION_1_3)
+		smccc_has_sve_hint = true;
 }
 
 enum arm_smccc_conduit arm_smccc_1_1_get_conduit(void)

include/linux/arm-smccc.h

@@ -280,6 +280,8 @@ u32 arm_smccc_get_version(void);
 
 void __init arm_smccc_version_init(u32 version, enum arm_smccc_conduit conduit);
 
+extern u64 smccc_has_sve_hint;
+
 /**
  * struct arm_smccc_res - Result from SMC/HVC call
  * @a0-a3 result values from registers 0 to 3
@@ -359,6 +361,15 @@ struct arm_smccc_quirk {
 	} state;
 };
 
+/**
+ * __arm_smccc_sve_check() - Set the SVE hint bit when doing SMC calls
+ *
+ * Sets the SMCCC hint bit to indicate if there is live state in the SVE
+ * registers, this modifies x0 in place and should never be called from C
+ * code.
+ */
+asmlinkage unsigned long __arm_smccc_sve_check(unsigned long x0);
+
 /**
  * __arm_smccc_smc() - make SMC calls
  * @a0-a7: arguments passed in registers 0 to 7
@@ -426,6 +437,20 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 
 #endif
 
+/* nVHE hypervisor doesn't have a current thread so needs separate checks */
+#if defined(CONFIG_ARM64_SVE) && !defined(__KVM_NVHE_HYPERVISOR__)
+
+#define SMCCC_SVE_CHECK ALTERNATIVE("nop \n",  "bl __arm_smccc_sve_check \n", \
+				    ARM64_SVE)
+#define smccc_sve_clobbers "x16", "x30", "cc",
+
+#else
+
+#define SMCCC_SVE_CHECK
+#define smccc_sve_clobbers
+
+#endif
+
 #define ___count_args(_0, _1, _2, _3, _4, _5, _6, _7, _8, x, ...) x
 
 #define __count_args(...)						\
@@ -493,7 +518,7 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 
 #define ___constraints(count)						\
 	: __constraint_read_ ## count					\
-	: "memory"
+	: smccc_sve_clobbers "memory"
 #define __constraints(count)	___constraints(count)
 
 /*
@@ -508,7 +533,8 @@ asmlinkage void __arm_smccc_hvc(unsigned long a0, unsigned long a1,
 		register unsigned long r2 asm("r2");			\
 		register unsigned long r3 asm("r3"); 			\
 		__declare_args(__count_args(__VA_ARGS__), __VA_ARGS__);	\
-		asm volatile(inst "\n" :				\
+		asm volatile(SMCCC_SVE_CHECK				\
+			     inst "\n" :				\
 			     "=r" (r0), "=r" (r1), "=r" (r2), "=r" (r3)	\
 			     __constraints(__count_args(__VA_ARGS__)));	\
 		if (___res)						\