From nobody Mon Feb 9 10:27:04 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2AA461F543F; Fri, 4 Apr 2025 13:28:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743773289; cv=none; b=HoVoGLIouxSQtvzgxo+v/HePH3kVnRz2uB7xTypEX8Bis7BNL6f8p7bqkJljU3jhpmv+Q88xRyR/48Q5oAHmwJZt7R2q0yJy9Kk8YcWU+WCpyAxWaQANE7WyVFIbiy73cK0jhgyPxZ07e1pvgAzBzrh3DfbLgA7z2w9WHQq/aGg= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743773289; c=relaxed/simple; bh=HAv7NsSiFTK50k4Hz83uGNas7UoL/L6QevslpZ79Hvo=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=U2LfWlFfnnPgQXkMRHbj5I9nXA2xnDuhorhUH2QGcKp4Z4Jm+9FDyhZIEEYTLvUA8OJkvPNQIs6UBfxLQvEHgkujhsQr4/MDQulKl8hYp7BCRYhZp8VaF8cZ1r5Gj9FhYymA5cxfaWZzS+KaePYn2E3ITGTltoAZgOCdUV49OgI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Z7uhIxgd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Z7uhIxgd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9ED04C4CEE8; Fri, 4 Apr 2025 13:28:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1743773288; bh=HAv7NsSiFTK50k4Hz83uGNas7UoL/L6QevslpZ79Hvo=; h=From:Date:Subject:References:In-Reply-To:To:Cc:From; b=Z7uhIxgdLxV6pUs71ncmGLGt+BUPrRLHK+LuVmSmPDqBEQnuAoMM1tvs+HdTku4Cz AEfN7oeLX/vGvT/vgIQq8lvJc9UWmZiwRs5ey2jm5o3vmb8YuwNM203Q4WzTY7eoZm VVL4Zl04SNHqYDYBcCcBBaIN6JpK0J1e/XmZlMXTBK6INNzoMS15rnAQhBkYspSN3Y 2m7hh+oJ6ldB3mX3Nf6v97aDQsWza+DhqC/t0FXwBnZ3mhLxrH7DPrPYZHSvcNa4Tq WsgnoFS9m0fn3V+cqPce9DHJ1cA7BSFYGcn07M7HQzhqtkNBV7DUQU9E0I9MGrdCAe ljE/zDrsiAapg== From: Mark Brown Date: Fri, 04 Apr 2025 14:23:45 +0100 Subject: [PATCH RESEND 6.1 12/12] KVM: arm64: Eagerly switch ZCR_EL{1,2} Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20250404-stable-sve-6-1-v1-12-cd5c9eb52d49@kernel.org> References: <20250404-stable-sve-6-1-v1-0-cd5c9eb52d49@kernel.org> In-Reply-To: <20250404-stable-sve-6-1-v1-0-cd5c9eb52d49@kernel.org> To: Catalin Marinas , Will Deacon , Marc Zyngier , James Morse , Suzuki K Poulose , Oliver Upton , Oleg Nesterov , Greg Kroah-Hartman Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvmarm@lists.cs.columbia.edu, Mark Brown , stable@vger.kernel.org, Mark Rutland , Fuad Tabba X-Mailer: b4 0.15-dev-c25d1 X-Developer-Signature: v=1; a=openpgp-sha256; l=13005; i=broonie@kernel.org; h=from:subject:message-id; bh=jBmdHfDYe/g7aZu/VzuVFBwig23sU36mad3b+6nEz3U=; b=owEBbQGS/pANAwAKASTWi3JdVIfQAcsmYgBn7942oibtfVGmbUhn+8y5LJjRXUBjShmUF50TpW0a 2dgkBISJATMEAAEKAB0WIQSt5miqZ1cYtZ/in+ok1otyXVSH0AUCZ+/eNgAKCRAk1otyXVSH0F9fB/ 484wab/Ot0iBMgHI4djOGBKHSbzTBl+yQZI30fRsmt7aMWGpY0KhPtv1ZlJjA4zDmwlVsAdq+HwaVv ajcbKZNtHtOZV3AHbXZ+XdVLTs5jeBi26PK+lgqO8l1IaML9DUyNDGkT3a6baymcrCKx93TxO/nQN5 xbIY0miyREqjWyKm/vMxE/c3fFq7AxLgXW1PlfXuqPbQwRDODaS/H8rRR4mU10fQzrWUAT8h5baeN1 0GHDi0nG9TojFjyx5y3YvVTu7L1TGyma0yjIOULwQRXcvZ7X0UPc0d3H0S8HVOiUp472YqQmptuDWC RSR9uYgamfigjM4p+qEuV9sgsw98KB X-Developer-Key: i=broonie@kernel.org; a=openpgp; fpr=3F2568AAC26998F9E813A1C5C3F436CA30F5D8EB From: Mark Rutland [ Upstream commit 59419f10045bc955d2229819c7cf7a8b0b9c5b59 ] In non-protected KVM modes, while the guest FPSIMD/SVE/SME state is live on= the CPU, the host's active SVE VL may differ from the guest's maximum SVE VL: * For VHE hosts, when a VM uses NV, ZCR_EL2 contains a value constrained by the guest hypervisor, which may be less than or equal to that guest's maximum VL. Note: in this case the value of ZCR_EL1 is immaterial due to E2H. * For nVHE/hVHE hosts, ZCR_EL1 contains a value written by the guest, which may be less than or greater than the guest's maximum VL. Note: in this case hyp code traps host SVE usage and lazily restores ZCR_EL2 to the host's maximum VL, which may be greater than the guest's maximum VL. This can be the case between exiting a guest and kvm_arch_vcpu_put_fp(). If a softirq is taken during this period and the softirq handler tries to use kernel-mode NEON, then the kernel will fail to save the guest's FPSIMD/SVE state, and will pend a SIGKILL for the current thread. This happens because kvm_arch_vcpu_ctxsync_fp() binds the guest's live FPSIMD/SVE state with the guest's maximum SVE VL, and fpsimd_save_user_state() verifies that the live SVE VL is as expected before attempting to save the register state: | if (WARN_ON(sve_get_vl() !=3D vl)) { | force_signal_inject(SIGKILL, SI_KERNEL, 0, 0); | return; | } Fix this and make this a bit easier to reason about by always eagerly switching ZCR_EL{1,2} at hyp during guest<->host transitions. With this happening, there's no need to trap host SVE usage, and the nVHE/nVHE __deactivate_cptr_traps() logic can be simplified to enable host access to all present FPSIMD/SVE/SME features. In protected nVHE/hVHE modes, the host's state is always saved/restored by hyp, and the guest's state is saved prior to exit to the host, so from the host's PoV the guest never has live FPSIMD/SVE/SME state, and the host's ZCR_EL1 is never clobbered by hyp. Fixes: 8c8010d69c132273 ("KVM: arm64: Save/restore SVE state for nVHE") Fixes: 2e3cf82063a00ea0 ("KVM: arm64: nv: Ensure correct VL is loaded befor= e saving SVE state") Signed-off-by: Mark Rutland Reviewed-by: Mark Brown Tested-by: Mark Brown Cc: Catalin Marinas Cc: Fuad Tabba Cc: Marc Zyngier Cc: Oliver Upton Cc: Will Deacon Reviewed-by: Oliver Upton Link: https://lore.kernel.org/r/20250210195226.1215254-9-mark.rutland@arm.c= om Signed-off-by: Marc Zyngier [ v6.6 lacks pKVM saving of host SVE state, pull in discovery of maximum host VL separately -- broonie ] Signed-off-by: Mark Brown --- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/include/asm/kvm_hyp.h | 1 + arch/arm64/kvm/fpsimd.c | 19 ++++++------ arch/arm64/kvm/hyp/entry.S | 5 +++ arch/arm64/kvm/hyp/include/hyp/switch.h | 55 +++++++++++++++++++++++++++++= ++++ arch/arm64/kvm/hyp/nvhe/hyp-main.c | 8 ++--- arch/arm64/kvm/hyp/nvhe/pkvm.c | 2 ++ arch/arm64/kvm/hyp/nvhe/switch.c | 30 +++++++++++------- arch/arm64/kvm/hyp/vhe/switch.c | 4 +++ arch/arm64/kvm/reset.c | 3 ++ 10 files changed, 103 insertions(+), 25 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm= _host.h index c13a0d5907e8..0935f9849510 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -67,6 +67,7 @@ enum kvm_mode kvm_get_mode(void); DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); =20 extern unsigned int kvm_sve_max_vl; +extern unsigned int kvm_host_sve_max_vl; int kvm_arm_init_sve(void); =20 u32 __attribute_const__ kvm_target_cpu(void); diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_= hyp.h index aa7fa2a08f06..1d0bb7624a1c 100644 --- a/arch/arm64/include/asm/kvm_hyp.h +++ b/arch/arm64/include/asm/kvm_hyp.h @@ -122,5 +122,6 @@ extern u64 kvm_nvhe_sym(id_aa64isar2_el1_sys_val); extern u64 kvm_nvhe_sym(id_aa64mmfr0_el1_sys_val); extern u64 kvm_nvhe_sym(id_aa64mmfr1_el1_sys_val); extern u64 kvm_nvhe_sym(id_aa64mmfr2_el1_sys_val); +extern unsigned int kvm_nvhe_sym(kvm_host_sve_max_vl); =20 #endif /* __ARM64_KVM_HYP_H__ */ diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index df050e4d3562..3fd86b71ee37 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -148,15 +148,16 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) local_irq_save(flags); =20 if (vcpu->arch.fp_state =3D=3D FP_STATE_GUEST_OWNED) { - if (vcpu_has_sve(vcpu)) { - __vcpu_sys_reg(vcpu, ZCR_EL1) =3D read_sysreg_el1(SYS_ZCR); - - /* Restore the VL that was saved when bound to the CPU */ - if (!has_vhe()) - sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1, - SYS_ZCR_EL1); - } - + /* + * Flush (save and invalidate) the fpsimd/sve state so that if + * the host tries to use fpsimd/sve, it's not using stale data + * from the guest. + * + * Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the + * context unconditionally, in both nVHE and VHE. This allows + * the kernel to restore the fpsimd/sve state, including ZCR_EL1 + * when needed. + */ fpsimd_save_and_flush_cpu_state(); } =20 diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S index 435346ea1504..d8c94c45cb2f 100644 --- a/arch/arm64/kvm/hyp/entry.S +++ b/arch/arm64/kvm/hyp/entry.S @@ -44,6 +44,11 @@ alternative_if ARM64_HAS_RAS_EXTN alternative_else_nop_endif mrs x1, isr_el1 cbz x1, 1f + + // Ensure that __guest_enter() always provides a context + // synchronization event so that callers don't need ISBs for anything + // that would usually be synchonized by the ERET. + isb mov x0, #ARM_EXCEPTION_IRQ ret =20 diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/i= nclude/hyp/switch.h index 0db90cb47308..275176e61d74 100644 --- a/arch/arm64/kvm/hyp/include/hyp/switch.h +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h @@ -167,6 +167,61 @@ static inline void __hyp_sve_restore_guest(struct kvm_= vcpu *vcpu) write_sysreg_el1(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR); } =20 +static inline void fpsimd_lazy_switch_to_guest(struct kvm_vcpu *vcpu) +{ + u64 zcr_el1, zcr_el2; + + if (!guest_owns_fp_regs(vcpu)) + return; + + if (vcpu_has_sve(vcpu)) { + zcr_el2 =3D vcpu_sve_max_vq(vcpu) - 1; + + write_sysreg_el2(zcr_el2, SYS_ZCR); + + zcr_el1 =3D __vcpu_sys_reg(vcpu, ZCR_EL1); + write_sysreg_el1(zcr_el1, SYS_ZCR); + } +} + +static inline void fpsimd_lazy_switch_to_host(struct kvm_vcpu *vcpu) +{ + u64 zcr_el1, zcr_el2; + + if (!guest_owns_fp_regs(vcpu)) + return; + + /* + * When the guest owns the FP regs, we know that guest+hyp traps for + * any FPSIMD/SVE/SME features exposed to the guest have been disabled + * by either fpsimd_lazy_switch_to_guest() or kvm_hyp_handle_fpsimd() + * prior to __guest_entry(). As __guest_entry() guarantees a context + * synchronization event, we don't need an ISB here to avoid taking + * traps for anything that was exposed to the guest. + */ + if (vcpu_has_sve(vcpu)) { + zcr_el1 =3D read_sysreg_el1(SYS_ZCR); + __vcpu_sys_reg(vcpu, ZCR_EL1) =3D zcr_el1; + + /* + * The guest's state is always saved using the guest's max VL. + * Ensure that the host has the guest's max VL active such that + * the host can save the guest's state lazily, but don't + * artificially restrict the host to the guest's max VL. + */ + if (has_vhe()) { + zcr_el2 =3D vcpu_sve_max_vq(vcpu) - 1; + write_sysreg_el2(zcr_el2, SYS_ZCR); + } else { + zcr_el2 =3D sve_vq_from_vl(kvm_host_sve_max_vl) - 1; + write_sysreg_el2(zcr_el2, SYS_ZCR); + + zcr_el1 =3D vcpu_sve_max_vq(vcpu) - 1; + write_sysreg_el1(zcr_el1, SYS_ZCR); + } + } +} + /* * We trap the first access to the FP/SIMD to save the host context and * restore the guest context lazily. diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/h= yp-main.c index 3cea4b6ac23e..b183cc866404 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -5,6 +5,7 @@ */ =20 #include +#include =20 #include #include @@ -25,7 +26,9 @@ static void handle___kvm_vcpu_run(struct kvm_cpu_context = *host_ctxt) { DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1); =20 + fpsimd_lazy_switch_to_guest(kern_hyp_va(vcpu)); cpu_reg(host_ctxt, 1) =3D __kvm_vcpu_run(kern_hyp_va(vcpu)); + fpsimd_lazy_switch_to_host(kern_hyp_va(vcpu)); } =20 static void handle___kvm_adjust_pc(struct kvm_cpu_context *host_ctxt) @@ -285,11 +288,6 @@ void handle_trap(struct kvm_cpu_context *host_ctxt) case ESR_ELx_EC_SMC64: handle_host_smc(host_ctxt); break; - case ESR_ELx_EC_SVE: - sysreg_clear_set(cptr_el2, CPTR_EL2_TZ, 0); - isb(); - sve_cond_update_zcr_vq(ZCR_ELx_LEN_MASK, SYS_ZCR_EL2); - break; case ESR_ELx_EC_IABT_LOW: case ESR_ELx_EC_DABT_LOW: handle_host_mem_abort(host_ctxt); diff --git a/arch/arm64/kvm/hyp/nvhe/pkvm.c b/arch/arm64/kvm/hyp/nvhe/pkvm.c index 93586bf80ec9..6042cdd3d887 100644 --- a/arch/arm64/kvm/hyp/nvhe/pkvm.c +++ b/arch/arm64/kvm/hyp/nvhe/pkvm.c @@ -9,6 +9,8 @@ #include #include =20 +unsigned int kvm_host_sve_max_vl; + /* * Set trap register values based on features in ID_AA64PFR0. */ diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/swi= tch.c index 58171926f9ba..47c7f3a675ae 100644 --- a/arch/arm64/kvm/hyp/nvhe/switch.c +++ b/arch/arm64/kvm/hyp/nvhe/switch.c @@ -40,6 +40,9 @@ static void __activate_cptr_traps(struct kvm_vcpu *vcpu) { u64 val =3D CPTR_EL2_TAM; /* Same bit irrespective of E2H */ =20 + if (!guest_owns_fp_regs(vcpu)) + __activate_traps_fpsimd32(vcpu); + /* !hVHE case upstream */ if (1) { val |=3D CPTR_EL2_TTA | CPTR_NVHE_EL2_RES1; @@ -55,12 +58,24 @@ static void __activate_cptr_traps(struct kvm_vcpu *vcpu) =20 if (!guest_owns_fp_regs(vcpu)) val |=3D CPTR_EL2_TFP; + + write_sysreg(val, cptr_el2); } +} =20 - if (!guest_owns_fp_regs(vcpu)) - __activate_traps_fpsimd32(vcpu); +static void __deactivate_cptr_traps(struct kvm_vcpu *vcpu) +{ + /* !hVHE case upstream */ + if (1) { + u64 val =3D CPTR_NVHE_EL2_RES1; =20 - write_sysreg(val, cptr_el2); + if (!cpus_have_final_cap(ARM64_SVE)) + val |=3D CPTR_EL2_TZ; + if (!cpus_have_final_cap(ARM64_SME)) + val |=3D CPTR_EL2_TSM; + + write_sysreg(val, cptr_el2); + } } =20 static void __activate_traps(struct kvm_vcpu *vcpu) @@ -89,7 +104,6 @@ static void __activate_traps(struct kvm_vcpu *vcpu) static void __deactivate_traps(struct kvm_vcpu *vcpu) { extern char __kvm_hyp_host_vector[]; - u64 cptr; =20 ___deactivate_traps(vcpu); =20 @@ -114,13 +128,7 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu) =20 write_sysreg(this_cpu_ptr(&kvm_init_params)->hcr_el2, hcr_el2); =20 - cptr =3D CPTR_EL2_DEFAULT; - if (vcpu_has_sve(vcpu) && (vcpu->arch.fp_state =3D=3D FP_STATE_GUEST_OWNE= D)) - cptr |=3D CPTR_EL2_TZ; - if (cpus_have_final_cap(ARM64_SME)) - cptr &=3D ~CPTR_EL2_TSM; - - write_sysreg(cptr, cptr_el2); + __deactivate_cptr_traps(vcpu); write_sysreg(__kvm_hyp_host_vector, vbar_el2); } =20 diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switc= h.c index f24569ac26c2..179152bb9e42 100644 --- a/arch/arm64/kvm/hyp/vhe/switch.c +++ b/arch/arm64/kvm/hyp/vhe/switch.c @@ -134,6 +134,8 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu) =20 sysreg_save_host_state_vhe(host_ctxt); =20 + fpsimd_lazy_switch_to_guest(vcpu); + /* * ARM erratum 1165522 requires us to configure both stage 1 and * stage 2 translation for the guest context before we clear @@ -164,6 +166,8 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu) =20 __deactivate_traps(vcpu); =20 + fpsimd_lazy_switch_to_host(vcpu); + sysreg_restore_host_state_vhe(host_ctxt); =20 if (vcpu->arch.fp_state =3D=3D FP_STATE_GUEST_OWNED) diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c index f9d070473614..54e00ee631a0 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -42,11 +42,14 @@ static u32 kvm_ipa_limit; PSR_AA32_I_BIT | PSR_AA32_F_BIT) =20 unsigned int kvm_sve_max_vl; +unsigned int kvm_host_sve_max_vl; =20 int kvm_arm_init_sve(void) { if (system_supports_sve()) { kvm_sve_max_vl =3D sve_max_virtualisable_vl(); + kvm_host_sve_max_vl =3D sve_max_vl(); + kvm_nvhe_sym(kvm_host_sve_max_vl) =3D kvm_host_sve_max_vl; =20 /* * The get_sve_reg()/set_sve_reg() ioctl interface will need --=20 2.39.5