Patch "arm64/fpsimd: Track the saved FPSIMD state type separately to TIF_SVE" has been added to the 6.1-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    arm64/fpsimd: Track the saved FPSIMD state type separately to TIF_SVE

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     arm64-fpsimd-track-the-saved-fpsimd-state-type-separately-to-tif_sve.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From stable+bounces-128301-greg=kroah.com@vger.kernel.org Fri Apr  4 15:28:10 2025
From: Mark Brown <broonie@kernel.org>
Date: Fri, 04 Apr 2025 14:23:35 +0100
Subject: arm64/fpsimd: Track the saved FPSIMD state type separately to TIF_SVE
To: Catalin Marinas <catalin.marinas@arm.com>,  Will Deacon <will@kernel.org>, Marc Zyngier <maz@kernel.org>,  James Morse <james.morse@arm.com>,  Suzuki K Poulose <suzuki.poulose@arm.com>,  Oliver Upton <oliver.upton@linux.dev>, Oleg Nesterov <oleg@redhat.com>,  Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,  kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu,  Mark Brown <broonie@kernel.org>, stable@vger.kernel.org,  Mark Rutland <mark.rutland@arm.com>
Message-ID: <20250404-stable-sve-6-1-v1-2-cd5c9eb52d49@kernel.org>

From: Mark Brown <broonie@kernel.org>

[ Upstream commit baa8515281b30861cff3da7db70662d2a25c6440 ]

When we save the state for the floating point registers this can be done
in the form visible through either the FPSIMD V registers or the SVE Z and
P registers. At present we track which format is currently used based on
TIF_SVE and the SME streaming mode state but particularly in the SVE case
this limits our options for optimising things, especially around syscalls.
Introduce a new enum which we place together with saved floating point
state in both thread_struct and the KVM guest state which explicitly
states which format is active and keep it up to date when we change it.

At present we do not use this state except to verify that it has the
expected value when loading the state, future patches will introduce
functional changes.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221115094640.112848-3-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
[ Mark: fix conflicts due to earlier backports ]
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/arm64/include/asm/fpsimd.h    |    2 -
 arch/arm64/include/asm/kvm_host.h  |   12 +++++++
 arch/arm64/include/asm/processor.h |    6 +++
 arch/arm64/kernel/fpsimd.c         |   58 +++++++++++++++++++++++++++----------
 arch/arm64/kernel/process.c        |    2 +
 arch/arm64/kernel/ptrace.c         |    3 +
 arch/arm64/kernel/signal.c         |    7 +++-
 arch/arm64/kvm/fpsimd.c            |    3 +
 8 files changed, 74 insertions(+), 19 deletions(-)

--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -61,7 +61,7 @@ extern void fpsimd_kvm_prepare(void);
 extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state,
 				     void *sve_state, unsigned int sve_vl,
 				     void *za_state, unsigned int sme_vl,
-				     u64 *svcr);
+				     u64 *svcr, enum fp_type *type);
 
 extern void fpsimd_flush_task_state(struct task_struct *target);
 extern void fpsimd_save_and_flush_cpu_state(void);
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -309,8 +309,18 @@ struct vcpu_reset_state {
 struct kvm_vcpu_arch {
 	struct kvm_cpu_context ctxt;
 
-	/* Guest floating point state */
+	/*
+	 * Guest floating point state
+	 *
+	 * The architecture has two main floating point extensions,
+	 * the original FPSIMD and SVE.  These have overlapping
+	 * register views, with the FPSIMD V registers occupying the
+	 * low 128 bits of the SVE Z registers.  When the core
+	 * floating point code saves the register state of a task it
+	 * records which view it saved in fp_type.
+	 */
 	void *sve_state;
+	enum fp_type fp_type;
 	unsigned int sve_max_vl;
 	u64 svcr;
 
--- a/arch/arm64/include/asm/processor.h
+++ b/arch/arm64/include/asm/processor.h
@@ -122,6 +122,11 @@ enum vec_type {
 	ARM64_VEC_MAX,
 };
 
+enum fp_type {
+	FP_STATE_FPSIMD,
+	FP_STATE_SVE,
+};
+
 struct cpu_context {
 	unsigned long x19;
 	unsigned long x20;
@@ -152,6 +157,7 @@ struct thread_struct {
 		struct user_fpsimd_state fpsimd_state;
 	} uw;
 
+	enum fp_type		fp_type;	/* registers FPSIMD or SVE? */
 	unsigned int		fpsimd_cpu;
 	void			*sve_state;	/* SVE registers, if any */
 	void			*za_state;	/* ZA register, if any */
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -125,6 +125,7 @@ struct fpsimd_last_state_struct {
 	u64 *svcr;
 	unsigned int sve_vl;
 	unsigned int sme_vl;
+	enum fp_type *fp_type;
 };
 
 static DEFINE_PER_CPU(struct fpsimd_last_state_struct, fpsimd_last_state);
@@ -330,15 +331,6 @@ void task_set_vl_onexec(struct task_stru
  *    The task can execute SVE instructions while in userspace without
  *    trapping to the kernel.
  *
- *    When stored, Z0-Z31 (incorporating Vn in bits[127:0] or the
- *    corresponding Zn), P0-P15 and FFR are encoded in
- *    task->thread.sve_state, formatted appropriately for vector
- *    length task->thread.sve_vl or, if SVCR.SM is set,
- *    task->thread.sme_vl.
- *
- *    task->thread.sve_state must point to a valid buffer at least
- *    sve_state_size(task) bytes in size.
- *
  *    During any syscall, the kernel may optionally clear TIF_SVE and
  *    discard the vector state except for the FPSIMD subset.
  *
@@ -348,7 +340,15 @@ void task_set_vl_onexec(struct task_stru
  *    do_sve_acc() to be called, which does some preparation and then
  *    sets TIF_SVE.
  *
- *    When stored, FPSIMD registers V0-V31 are encoded in
+ * During any syscall, the kernel may optionally clear TIF_SVE and
+ * discard the vector state except for the FPSIMD subset.
+ *
+ * The data will be stored in one of two formats:
+ *
+ *  * FPSIMD only - FP_STATE_FPSIMD:
+ *
+ *    When the FPSIMD only state stored task->thread.fp_type is set to
+ *    FP_STATE_FPSIMD, the FPSIMD registers V0-V31 are encoded in
  *    task->thread.uw.fpsimd_state; bits [max : 128] for each of Z0-Z31 are
  *    logically zero but not stored anywhere; P0-P15 and FFR are not
  *    stored and have unspecified values from userspace's point of
@@ -358,6 +358,19 @@ void task_set_vl_onexec(struct task_stru
  *    task->thread.sve_state does not need to be non-NULL, valid or any
  *    particular size: it must not be dereferenced.
  *
+ *  * SVE state - FP_STATE_SVE:
+ *
+ *    When the full SVE state is stored task->thread.fp_type is set to
+ *    FP_STATE_SVE and Z0-Z31 (incorporating Vn in bits[127:0] or the
+ *    corresponding Zn), P0-P15 and FFR are encoded in in
+ *    task->thread.sve_state, formatted appropriately for vector
+ *    length task->thread.sve_vl or, if SVCR.SM is set,
+ *    task->thread.sme_vl. The storage for the vector registers in
+ *    task->thread.uw.fpsimd_state should be ignored.
+ *
+ *    task->thread.sve_state must point to a valid buffer at least
+ *    sve_state_size(task) bytes in size.
+ *
  *  * FPSR and FPCR are always stored in task->thread.uw.fpsimd_state
  *    irrespective of whether TIF_SVE is clear or set, since these are
  *    not vector length dependent.
@@ -404,12 +417,15 @@ static void task_fpsimd_load(void)
 		}
 	}
 
-	if (restore_sve_regs)
+	if (restore_sve_regs) {
+		WARN_ON_ONCE(current->thread.fp_type != FP_STATE_SVE);
 		sve_load_state(sve_pffr(&current->thread),
 			       &current->thread.uw.fpsimd_state.fpsr,
 			       restore_ffr);
-	else
+	} else {
+		WARN_ON_ONCE(current->thread.fp_type != FP_STATE_FPSIMD);
 		fpsimd_load_state(&current->thread.uw.fpsimd_state);
+	}
 }
 
 /*
@@ -474,8 +490,10 @@ static void fpsimd_save(void)
 		sve_save_state((char *)last->sve_state +
 					sve_ffr_offset(vl),
 			       &last->st->fpsr, save_ffr);
+		*last->fp_type = FP_STATE_SVE;
 	} else {
 		fpsimd_save_state(last->st);
+		*last->fp_type = FP_STATE_FPSIMD;
 	}
 }
 
@@ -851,8 +869,10 @@ int vec_set_vector_length(struct task_st
 
 	fpsimd_flush_task_state(task);
 	if (test_and_clear_tsk_thread_flag(task, TIF_SVE) ||
-	    thread_sm_enabled(&task->thread))
+	    thread_sm_enabled(&task->thread)) {
 		sve_to_fpsimd(task);
+		task->thread.fp_type = FP_STATE_FPSIMD;
+	}
 
 	if (system_supports_sme()) {
 		if (type == ARM64_VEC_SME ||
@@ -1383,6 +1403,7 @@ static void sve_init_regs(void)
 		fpsimd_bind_task_to_cpu();
 	} else {
 		fpsimd_to_sve(current);
+		current->thread.fp_type = FP_STATE_SVE;
 		fpsimd_flush_task_state(current);
 	}
 }
@@ -1612,6 +1633,8 @@ void fpsimd_flush_thread(void)
 		current->thread.svcr = 0;
 	}
 
+	current->thread.fp_type = FP_STATE_FPSIMD;
+
 	put_cpu_fpsimd_context();
 	kfree(sve_state);
 	kfree(za_state);
@@ -1660,8 +1683,10 @@ void fpsimd_kvm_prepare(void)
 	 */
 	get_cpu_fpsimd_context();
 
-	if (test_and_clear_thread_flag(TIF_SVE))
+	if (test_and_clear_thread_flag(TIF_SVE)) {
 		sve_to_fpsimd(current);
+		current->thread.fp_type = FP_STATE_FPSIMD;
+	}
 
 	put_cpu_fpsimd_context();
 }
@@ -1683,6 +1708,7 @@ static void fpsimd_bind_task_to_cpu(void
 	last->sve_vl = task_get_sve_vl(current);
 	last->sme_vl = task_get_sme_vl(current);
 	last->svcr = &current->thread.svcr;
+	last->fp_type = &current->thread.fp_type;
 	current->thread.fpsimd_cpu = smp_processor_id();
 
 	/*
@@ -1706,7 +1732,8 @@ static void fpsimd_bind_task_to_cpu(void
 
 void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *st, void *sve_state,
 			      unsigned int sve_vl, void *za_state,
-			      unsigned int sme_vl, u64 *svcr)
+			      unsigned int sme_vl, u64 *svcr,
+			      enum fp_type *type)
 {
 	struct fpsimd_last_state_struct *last =
 		this_cpu_ptr(&fpsimd_last_state);
@@ -1720,6 +1747,7 @@ void fpsimd_bind_state_to_cpu(struct use
 	last->za_state = za_state;
 	last->sve_vl = sve_vl;
 	last->sme_vl = sme_vl;
+	last->fp_type = type;
 }
 
 /*
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -331,6 +331,8 @@ int arch_dup_task_struct(struct task_str
 		clear_tsk_thread_flag(dst, TIF_SME);
 	}
 
+	dst->thread.fp_type = FP_STATE_FPSIMD;
+
 	/* clear any pending asynchronous tag fault raised by the parent */
 	clear_tsk_thread_flag(dst, TIF_MTE_ASYNC_FAULT);
 
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -917,6 +917,7 @@ static int sve_set_common(struct task_st
 		clear_tsk_thread_flag(target, TIF_SVE);
 		if (type == ARM64_VEC_SME)
 			fpsimd_force_sync_to_sve(target);
+		target->thread.fp_type = FP_STATE_FPSIMD;
 		goto out;
 	}
 
@@ -939,6 +940,7 @@ static int sve_set_common(struct task_st
 	if (!target->thread.sve_state) {
 		ret = -ENOMEM;
 		clear_tsk_thread_flag(target, TIF_SVE);
+		target->thread.fp_type = FP_STATE_FPSIMD;
 		goto out;
 	}
 
@@ -952,6 +954,7 @@ static int sve_set_common(struct task_st
 	fpsimd_sync_to_sve(target);
 	if (type == ARM64_VEC_SVE)
 		set_tsk_thread_flag(target, TIF_SVE);
+	target->thread.fp_type = FP_STATE_SVE;
 
 	BUILD_BUG_ON(SVE_PT_SVE_OFFSET != sizeof(header));
 	start = SVE_PT_SVE_OFFSET;
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -207,6 +207,7 @@ static int restore_fpsimd_context(struct
 	__get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
 
 	clear_thread_flag(TIF_SVE);
+	current->thread.fp_type = FP_STATE_FPSIMD;
 
 	/* load the hardware registers from the fpsimd_state structure */
 	if (!err)
@@ -297,6 +298,7 @@ static int restore_sve_fpsimd_context(st
 	if (sve.head.size <= sizeof(*user->sve)) {
 		clear_thread_flag(TIF_SVE);
 		current->thread.svcr &= ~SVCR_SM_MASK;
+		current->thread.fp_type = FP_STATE_FPSIMD;
 		goto fpsimd_only;
 	}
 
@@ -332,6 +334,7 @@ static int restore_sve_fpsimd_context(st
 		current->thread.svcr |= SVCR_SM_MASK;
 	else
 		set_thread_flag(TIF_SVE);
+	current->thread.fp_type = FP_STATE_SVE;
 
 fpsimd_only:
 	/* copy the FP and status/control registers */
@@ -937,9 +940,11 @@ static void setup_return(struct pt_regs
 		 * FPSIMD register state - flush the saved FPSIMD
 		 * register state in case it gets loaded.
 		 */
-		if (current->thread.svcr & SVCR_SM_MASK)
+		if (current->thread.svcr & SVCR_SM_MASK) {
 			memset(&current->thread.uw.fpsimd_state, 0,
 			       sizeof(current->thread.uw.fpsimd_state));
+			current->thread.fp_type = FP_STATE_FPSIMD;
+		}
 
 		current->thread.svcr &= ~(SVCR_ZA_MASK |
 					  SVCR_SM_MASK);
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -140,7 +140,8 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm
 		fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.fp_regs,
 					 vcpu->arch.sve_state,
 					 vcpu->arch.sve_max_vl,
-					 NULL, 0, &vcpu->arch.svcr);
+					 NULL, 0, &vcpu->arch.svcr,
+					 &vcpu->arch.fp_type);
 
 		clear_thread_flag(TIF_FOREIGN_FPSTATE);
 		update_thread_flag(TIF_SVE, vcpu_has_sve(vcpu));


Patches currently in stable-queue which might be from broonie@kernel.org are

queue-6.1/kvm-arm64-remove-host-fpsimd-saving-for-non-protected-kvm.patch
queue-6.1/spi-cadence-qspi-fix-probe-on-am62a-lp-sk.patch
queue-6.1/asoc-qdsp6-q6asm-dai-fix-q6asm_dai_compr_set_params-error-path.patch
queue-6.1/asoc-qdsp6-q6apm-dai-fix-capture-pipeline-overruns.patch
queue-6.1/kvm-arm64-mark-some-header-functions-as-inline.patch
queue-6.1/kvm-arm64-eagerly-switch-zcr_el-1-2.patch
queue-6.1/kvm-arm64-unconditionally-save-flush-host-fpsimd-sve-sme-state.patch
queue-6.1/asoc-amd-add-dmi-quirk-for-acp6x-mic-support.patch
queue-6.1/kvm-arm64-refactor-exit-handlers.patch
queue-6.1/asoc-qdsp6-q6apm-dai-set-10-ms-period-and-buffer-alignment.patch
queue-6.1/asoc-codecs-lpass-wsa-macro-fix-vi-feedback-rate.patch
queue-6.1/arm64-fpsimd-track-the-saved-fpsimd-state-type-separately-to-tif_sve.patch
queue-6.1/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.zen.patch
queue-6.1/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.smen.patch
queue-6.1/asoc-fsl_audmix-register-card-device-depends-on-dais.patch
queue-6.1/arm64-fpsimd-have-kvm-explicitly-say-which-fp-registers-to-save.patch
queue-6.1/kvm-arm64-discard-any-sve-state-when-entering-kvm-guests.patch
queue-6.1/arm64-fpsimd-stop-using-tif_sve-to-manage-register-saving-in-kvm.patch
queue-6.1/asoc-codecs-lpass-wsa-macro-fix-logic-of-enabling-vi-channels.patch
queue-6.1/kvm-arm64-calculate-cptr_el2-traps-on-activating-traps.patch