Patch "KVM: arm64: Remove host FPSIMD saving for non-protected KVM" has been added to the 5.15-stable tree

[gregkh at linuxfoundation.org]

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

    KVM: arm64: Remove host FPSIMD saving for non-protected KVM

to the 5.15-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:
     kvm-arm64-remove-host-fpsimd-saving-for-non-protected-kvm.patch
and it can be found in the queue-5.15 subdirectory.

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


>From broonie at kernel.org Tue Apr  8 20:22:43 2025
From: Mark Brown <broonie at kernel.org>
Date: Tue, 08 Apr 2025 19:10:03 +0100
Subject: KVM: arm64: Remove host FPSIMD saving for non-protected KVM
To: Greg Kroah-Hartman <gregkh at linuxfoundation.org>,  Marc Zyngier <maz at kernel.org>, James Morse <james.morse at arm.com>,  Suzuki K Poulose <suzuki.poulose at arm.com>,  Catalin Marinas <catalin.marinas at arm.com>, Will Deacon <will at kernel.org>,  Oleg Nesterov <oleg at redhat.com>, Oliver Upton <oliver.upton at linux.dev>
Cc: linux-arm-kernel at lists.infradead.org, kvmarm at lists.cs.columbia.edu,  linux-kernel at vger.kernel.org, stable at vger.kernel.org,  Mark Brown <broonie at kernel.org>, Mark Rutland <mark.rutland at arm.com>,  Fuad Tabba <tabba at google.com>
Message-ID: <20250408-stable-sve-5-15-v3-8-ca9a6b850f55 at kernel.org>

From: Mark Rutland <mark.rutland at arm.com>

[ Upstream commit 8eca7f6d5100b6997df4f532090bc3f7e0203bef ]

Now that the host eagerly saves its own FPSIMD/SVE/SME state,
non-protected KVM never needs to save the host FPSIMD/SVE/SME state,
and the code to do this is never used. Protected KVM still needs to
save/restore the host FPSIMD/SVE state to avoid leaking guest state to
the host (and to avoid revealing to the host whether the guest used
FPSIMD/SVE/SME), and that code needs to be retained.

Remove the unused code and data structures.

To avoid the need for a stub copy of kvm_hyp_save_fpsimd_host() in the
VHE hyp code, the nVHE/hVHE version is moved into the shared switch
header, where it is only invoked when KVM is in protected mode.

Signed-off-by: Mark Rutland <mark.rutland at arm.com>
Reviewed-by: Mark Brown <broonie at kernel.org>
Tested-by: Mark Brown <broonie at kernel.org>
Acked-by: Will Deacon <will at kernel.org>
Cc: Catalin Marinas <catalin.marinas at arm.com>
Cc: Fuad Tabba <tabba at google.com>
Cc: Marc Zyngier <maz at kernel.org>
Cc: Oliver Upton <oliver.upton at linux.dev>
Reviewed-by: Oliver Upton <oliver.upton at linux.dev>
Link: https://lore.kernel.org/r/20250210195226.1215254-3-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz at kernel.org>
Signed-off-by: Mark Brown <broonie at kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
---
 arch/arm64/include/asm/kvm_host.h       |    1 -
 arch/arm64/kvm/fpsimd.c                 |    1 -
 arch/arm64/kvm/hyp/include/hyp/switch.h |    6 +-----
 3 files changed, 1 insertion(+), 7 deletions(-)

--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -333,7 +333,6 @@ struct kvm_vcpu_arch {
 	struct kvm_guest_debug_arch external_debug_state;
 
 	struct thread_info *host_thread_info;	/* hyp VA */
-	struct user_fpsimd_state *host_fpsimd_state;	/* hyp VA */
 
 	struct {
 		/* {Break,watch}point registers */
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -55,7 +55,6 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_
 	}
 
 	vcpu->arch.host_thread_info = kern_hyp_va(ti);
-	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
 error:
 	return ret;
 }
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -251,11 +251,7 @@ static inline bool __hyp_handle_fpsimd(s
 	}
 	isb();
 
-	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
-		__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
-		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;
-	}
-
+	/* Restore the guest state */
 	if (sve_guest)
 		__hyp_sve_restore_guest(vcpu);
 	else


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

queue-5.15/kvm-arm64-remove-host-fpsimd-saving-for-non-protected-kvm.patch
queue-5.15/spi-cadence-qspi-fix-probe-on-am62a-lp-sk.patch
queue-5.15/asoc-qdsp6-q6asm-dai-fix-q6asm_dai_compr_set_params-error-path.patch
queue-5.15/kvm-arm64-eagerly-switch-zcr_el-1-2.patch
queue-5.15/kvm-arm64-unconditionally-save-flush-host-fpsimd-sve-sme-state.patch
queue-5.15/kvm-arm64-always-start-with-clearing-sve-flag-on-load.patch
queue-5.15/asoc-codecs-lpass-wsa-macro-fix-vi-feedback-rate.patch
queue-5.15/arm64-fpsimd-track-the-saved-fpsimd-state-type-separately-to-tif_sve.patch
queue-5.15/kvm-arm64-get-rid-of-host-sve-tracking-saving.patch
queue-5.15/kvm-arm64-remove-vhe-host-restore-of-cpacr_el1.zen.patch
queue-5.15/asoc-fsl_audmix-register-card-device-depends-on-dais.patch
queue-5.15/arm64-fpsimd-have-kvm-explicitly-say-which-fp-registers-to-save.patch
queue-5.15/kvm-arm64-discard-any-sve-state-when-entering-kvm-guests.patch
queue-5.15/arm64-fpsimd-stop-using-tif_sve-to-manage-register-saving-in-kvm.patch
queue-5.15/asoc-codecs-lpass-wsa-macro-fix-logic-of-enabling-vi-channels.patch
queue-5.15/kvm-arm64-calculate-cptr_el2-traps-on-activating-traps.patch