Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

Pull arm64 fixes from Will Deacon:
 "Here is a (hopefully) final round of arm64 fixes for 6.12 that address
  some user-visible floating point register corruption. Both of the
  Marks have been working on this for a couple of weeks and we've ended
  up in a position where SVE is solid but SME still has enough pending
  issues that the most pragmatic solution for the release and stable
  backports is to disable the feature. Yes, it's a shame, but the
  hardware is rare as hen's teeth at the moment and we're better off
  getting back to a known good state before fixing it all properly.
  We're also improving the selftests for 6.13 to help avoid merging
  broken code in the future.

  Anyway, the good news is that we're removing a lot more code than
  we're adding.

  Summary:

   - Fix handling of SVE traps from userspace on preemptible kernels
     when converting the saved floating point state into SVE state.

   - Remove broken support for the SMCCCv1.3 "SVE discard hint"
     optimisation.

   - Disable SME support, as the current support code suffers from
     numerous issues around signal delivery, ptrace access and
     context-switch which can lead to user-visible corruption of the
     register state"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: Kconfig: Make SME depend on BROKEN for now
  arm64: smccc: Remove broken support for SMCCCv1.3 SVE discard hint
  arm64/sve: Discard stale CPU state when handling SVE traps

3 files changed, 5 insertions, 32 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index fd9df6dcc593..70d7f4f20225 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2214,6 +2214,7 @@ config ARM64_SME
 	bool "ARM Scalable Matrix Extension support"
 	default y
 	depends on ARM64_SVE
+	depends on BROKEN
 	help
 	  The Scalable Matrix Extension (SME) is an extension to the AArch64
 	  execution state which utilises a substantial subset of the SVE
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 77006df20a75..6d21971ae559 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1367,6 +1367,7 @@ static void sve_init_regs(void)
 	} else {
 		fpsimd_to_sve(current);
 		current->thread.fp_type = FP_STATE_SVE;
+		fpsimd_flush_task_state(current);
 	}
 }
 
diff --git a/arch/arm64/kernel/smccc-call.S b/arch/arm64/kernel/smccc-call.S
index 487381164ff6..2def9d0dd3dd 100644
--- a/arch/arm64/kernel/smccc-call.S
+++ b/arch/arm64/kernel/smccc-call.S
@@ -7,48 +7,19 @@
 
 #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, #16]
+	ldr	x4, [sp]
 	stp	x0, x1, [x4, #ARM_SMCCC_RES_X0_OFFS]
 	stp	x2, x3, [x4, #ARM_SMCCC_RES_X2_OFFS]
-	ldr	x4, [sp, #24]
+	ldr	x4, [sp, #8]
 	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:	ldp     x29, x30, [sp], #16
-	ret
+1:	ret
 	.endm
 
 /*