linux-kernel - [PATCH 6.1 06/12] KVM: arm64: Remove host FPSIMD saving for non-protected KVM

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250325-stable-sve-6-1-v1-6-83259d427d84@kernel.org>
Date: Tue, 25 Mar 2025 18:48:20 +0000
From: Mark Brown <broonie@...nel.org>
To: Catalin Marinas <catalin.marinas@....com>, 
 Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>, 
 James Morse <james.morse@....com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, 
 Oliver Upton <oliver.upton@...ux.dev>, Oleg Nesterov <oleg@...hat.com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 kvmarm@...ts.linux.dev, kvmarm@...ts.cs.columbia.edu, 
 Mark Brown <broonie@...nel.org>, Mark Rutland <mark.rutland@....com>, 
 Fuad Tabba <tabba@...gle.com>
Subject: [PATCH 6.1 06/12] KVM: arm64: Remove host FPSIMD saving for
 non-protected KVM

From: Mark Rutland <mark.rutland@....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@....com>
Reviewed-by: Mark Brown <broonie@...nel.org>
Tested-by: Mark Brown <broonie@...nel.org>
Acked-by: Will Deacon <will@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Fuad Tabba <tabba@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>
Cc: Oliver Upton <oliver.upton@...ux.dev>
Reviewed-by: Oliver Upton <oliver.upton@...ux.dev>
Link: https://lore.kernel.org/r/20250210195226.1215254-3-mark.rutland@arm.com
Signed-off-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/include/asm/kvm_host.h       | 1 -
 arch/arm64/kvm/fpsimd.c                 | 2 --
 arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ----
 3 files changed, 7 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 0e9b093adc6726770e0ff701ae9441ab31e448a5..7f187ac24e5d37369ef0af4154fdb17890f28798 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -380,7 +380,6 @@ struct kvm_vcpu_arch {
 	struct kvm_guest_debug_arch vcpu_debug_state;
 	struct kvm_guest_debug_arch external_debug_state;
 
-	struct user_fpsimd_state *host_fpsimd_state;	/* hyp VA */
 	struct task_struct *parent_task;
 
 	struct {
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 1765f723afd493255010c71d9bd4a2ddef819565..ee7c59f96451fcb217957c9fdbbd76046393bef3 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -49,8 +49,6 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
 	if (ret)
 		return ret;
 
-	vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
-
 	/*
 	 * We need to keep current's task_struct pinned until its data has been
 	 * unshared with the hypervisor to make sure it is not re-used by the
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 081aca8f432ef3ee303feb437a9556a0e917d6c1..50e6f3fcc27cd35822246144c1e5f7761e316746 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -207,10 +207,6 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
 	}
 	isb();
 
-	/* Write out the host state if it's in the registers */
-	if (vcpu->arch.fp_state == FP_STATE_HOST_OWNED)
-		__fpsimd_save_state(vcpu->arch.host_fpsimd_state);
-
 	/* Restore the guest state */
 	if (sve_guest)
 		__hyp_sve_restore_guest(vcpu);

-- 
2.39.5