From: Vincent Donnefort <vdonnefort@google.com>
To: Fuad Tabba <tabba@google.com>
Cc: Marc Zyngier <maz@kernel.org>, Oliver Upton <oupton@kernel.org>,
kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, Joey Gouly <joey.gouly@arm.com>,
Steffen Eiden <seiden@linux.ibm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Quentin Perret <qperret@google.com>,
Sebastian Ene <sebastianene@google.com>,
Hyunwoo Kim <imv4bel@gmail.com>
Subject: Re: [PATCH v2 3/8] KVM: arm64: Factor out reusable vCPU reset helpers
Date: Fri, 19 Jun 2026 14:29:18 +0100 [thread overview]
Message-ID: <ajVELlJ4hMnXVFMR@google.com> (raw)
In-Reply-To: <20260619070719.812227-4-tabba@google.com>
On Fri, Jun 19, 2026 at 08:07:14AM +0100, Fuad Tabba wrote:
> Pull the reusable pieces out of kvm_reset_vcpu(): expose the reset
> PSTATE values in kvm_arm.h, and split the core register reset and the
> PSCI-driven reset into kvm_reset_vcpu_core() and kvm_reset_vcpu_psci().
> A follow-up series reuses these to reset protected vCPUs at EL2.
>
> No functional change intended.
>
> Signed-off-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
> ---
> arch/arm64/include/asm/kvm_arm.h | 12 ++++++
> arch/arm64/include/asm/kvm_emulate.h | 57 ++++++++++++++++++++++++++
> arch/arm64/kvm/reset.c | 60 ++--------------------------
> 3 files changed, 72 insertions(+), 57 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 3f9233b5a130..aba4ec09acd2 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -348,4 +348,16 @@
> { PSR_AA32_MODE_UND, "32-bit UND" }, \
> { PSR_AA32_MODE_SYS, "32-bit SYS" }
>
> +/*
> + * ARMv8 Reset Values
> + */
> +#define VCPU_RESET_PSTATE_EL1 (PSR_MODE_EL1h | PSR_A_BIT | PSR_I_BIT | \
> + PSR_F_BIT | PSR_D_BIT)
> +
> +#define VCPU_RESET_PSTATE_EL2 (PSR_MODE_EL2h | PSR_A_BIT | PSR_I_BIT | \
> + PSR_F_BIT | PSR_D_BIT)
> +
> +#define VCPU_RESET_PSTATE_SVC (PSR_AA32_MODE_SVC | PSR_AA32_A_BIT | \
> + PSR_AA32_I_BIT | PSR_AA32_F_BIT)
> +
> #endif /* __ARM64_KVM_ARM_H__ */
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 80b30fead3d1..2385d8855fcf 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -704,4 +704,61 @@ static inline void vcpu_set_hcrx(struct kvm_vcpu *vcpu)
> vcpu->arch.hcrx_el2 |= HCRX_EL2_EnASR;
> }
> }
> +
> +/* Reset a vcpu's core registers. */
> +static inline void kvm_reset_vcpu_core(struct kvm_vcpu *vcpu)
> +{
> + u32 pstate;
> +
> + if (vcpu_el1_is_32bit(vcpu))
> + pstate = VCPU_RESET_PSTATE_SVC;
> + else if (vcpu_has_nv(vcpu))
> + pstate = VCPU_RESET_PSTATE_EL2;
> + else
> + pstate = VCPU_RESET_PSTATE_EL1;
> +
> + /* Reset core registers */
> + memset(vcpu_gp_regs(vcpu), 0, sizeof(*vcpu_gp_regs(vcpu)));
> + memset(&vcpu->arch.ctxt.fp_regs, 0, sizeof(vcpu->arch.ctxt.fp_regs));
> + vcpu->arch.ctxt.spsr_abt = 0;
> + vcpu->arch.ctxt.spsr_und = 0;
> + vcpu->arch.ctxt.spsr_irq = 0;
> + vcpu->arch.ctxt.spsr_fiq = 0;
> + vcpu_gp_regs(vcpu)->pstate = pstate;
> +}
> +
> +/* PSCI reset handling for a vcpu. */
> +static inline void kvm_reset_vcpu_psci(struct kvm_vcpu *vcpu,
> + struct vcpu_reset_state *reset_state)
> +{
> + unsigned long target_pc = reset_state->pc;
> +
> + /* Gracefully handle Thumb2 entry point */
> + if (vcpu_mode_is_32bit(vcpu) && (target_pc & 1)) {
> + target_pc &= ~1UL;
> + vcpu_set_thumb(vcpu);
> + }
> +
> + /* Propagate caller endianness */
> + if (reset_state->be)
> + kvm_vcpu_set_be(vcpu);
> +
> + *vcpu_pc(vcpu) = target_pc;
> +
> + /*
> + * We may come from a state where either a PC update was
> + * pending (SMC call resulting in PC being increpented to
> + * skip the SMC) or a pending exception. Make sure we get
> + * rid of all that, as this cannot be valid out of reset.
> + *
> + * Note that clearing the exception mask also clears PC
> + * updates, but that's an implementation detail, and we
> + * really want to make it explicit.
> + */
> + vcpu_clear_flag(vcpu, PENDING_EXCEPTION);
> + vcpu_clear_flag(vcpu, EXCEPT_MASK);
> + vcpu_clear_flag(vcpu, INCREMENT_PC);
> + vcpu_set_reg(vcpu, 0, reset_state->r0);
> +}
> +
> #endif /* __ARM64_KVM_EMULATE_H__ */
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index b963fd975aac..10eb7249aa9e 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -34,18 +34,6 @@
> static u32 __ro_after_init kvm_ipa_limit;
> unsigned int __ro_after_init kvm_host_sve_max_vl;
>
> -/*
> - * ARMv8 Reset Values
> - */
> -#define VCPU_RESET_PSTATE_EL1 (PSR_MODE_EL1h | PSR_A_BIT | PSR_I_BIT | \
> - PSR_F_BIT | PSR_D_BIT)
> -
> -#define VCPU_RESET_PSTATE_EL2 (PSR_MODE_EL2h | PSR_A_BIT | PSR_I_BIT | \
> - PSR_F_BIT | PSR_D_BIT)
> -
> -#define VCPU_RESET_PSTATE_SVC (PSR_AA32_MODE_SVC | PSR_AA32_A_BIT | \
> - PSR_AA32_I_BIT | PSR_AA32_F_BIT)
> -
> unsigned int __ro_after_init kvm_sve_max_vl;
>
> int __init kvm_arm_init_sve(void)
> @@ -191,7 +179,6 @@ void kvm_reset_vcpu(struct kvm_vcpu *vcpu)
> {
> struct vcpu_reset_state reset_state;
> bool loaded;
> - u32 pstate;
>
> spin_lock(&vcpu->arch.mp_state_lock);
> reset_state = vcpu->arch.reset_state;
> @@ -210,21 +197,8 @@ void kvm_reset_vcpu(struct kvm_vcpu *vcpu)
> kvm_vcpu_reset_sve(vcpu);
> }
>
> - if (vcpu_el1_is_32bit(vcpu))
> - pstate = VCPU_RESET_PSTATE_SVC;
> - else if (vcpu_has_nv(vcpu))
> - pstate = VCPU_RESET_PSTATE_EL2;
> - else
> - pstate = VCPU_RESET_PSTATE_EL1;
> -
> /* Reset core registers */
> - memset(vcpu_gp_regs(vcpu), 0, sizeof(*vcpu_gp_regs(vcpu)));
> - memset(&vcpu->arch.ctxt.fp_regs, 0, sizeof(vcpu->arch.ctxt.fp_regs));
> - vcpu->arch.ctxt.spsr_abt = 0;
> - vcpu->arch.ctxt.spsr_und = 0;
> - vcpu->arch.ctxt.spsr_irq = 0;
> - vcpu->arch.ctxt.spsr_fiq = 0;
> - vcpu_gp_regs(vcpu)->pstate = pstate;
> + kvm_reset_vcpu_core(vcpu);
>
> /* Reset system registers */
> kvm_reset_sys_regs(vcpu);
> @@ -233,36 +207,8 @@ void kvm_reset_vcpu(struct kvm_vcpu *vcpu)
> * Additional reset state handling that PSCI may have imposed on us.
> * Must be done after all the sys_reg reset.
> */
> - if (reset_state.reset) {
> - unsigned long target_pc = reset_state.pc;
> -
> - /* Gracefully handle Thumb2 entry point */
> - if (vcpu_mode_is_32bit(vcpu) && (target_pc & 1)) {
> - target_pc &= ~1UL;
> - vcpu_set_thumb(vcpu);
> - }
> -
> - /* Propagate caller endianness */
> - if (reset_state.be)
> - kvm_vcpu_set_be(vcpu);
> -
> - *vcpu_pc(vcpu) = target_pc;
> -
> - /*
> - * We may come from a state where either a PC update was
> - * pending (SMC call resulting in PC being increpented to
> - * skip the SMC) or a pending exception. Make sure we get
> - * rid of all that, as this cannot be valid out of reset.
> - *
> - * Note that clearing the exception mask also clears PC
> - * updates, but that's an implementation detail, and we
> - * really want to make it explicit.
> - */
> - vcpu_clear_flag(vcpu, PENDING_EXCEPTION);
> - vcpu_clear_flag(vcpu, EXCEPT_MASK);
> - vcpu_clear_flag(vcpu, INCREMENT_PC);
> - vcpu_set_reg(vcpu, 0, reset_state.r0);
> - }
> + if (reset_state.reset)
> + kvm_reset_vcpu_psci(vcpu, &reset_state);
>
> /* Reset timer */
> kvm_timer_vcpu_reset(vcpu);
> --
> 2.55.0.rc0.738.g0c8ab3ebcc-goog
>
next prev parent reply other threads:[~2026-06-19 13:29 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-19 7:07 [PATCH v2 0/8] KVM: arm64: Rework pKVM vCPU state synchronisation Fuad Tabba
2026-06-19 7:07 ` [PATCH v2 1/8] KVM: arm64: Extract MPIDR computation into a shared header Fuad Tabba
2026-06-19 13:24 ` Vincent Donnefort
2026-06-19 7:07 ` [PATCH v2 2/8] KVM: arm64: Make vcpu_{read,write}_sys_reg available to HYP code Fuad Tabba
2026-06-19 13:26 ` Vincent Donnefort
2026-06-19 7:07 ` [PATCH v2 3/8] KVM: arm64: Factor out reusable vCPU reset helpers Fuad Tabba
2026-06-19 13:29 ` Vincent Donnefort [this message]
2026-06-19 7:07 ` [PATCH v2 4/8] KVM: arm64: Move PSCI helper functions to a shared header Fuad Tabba
2026-06-19 13:30 ` Vincent Donnefort
2026-06-19 7:07 ` [PATCH v2 5/8] KVM: arm64: Add host and hypervisor vCPU lookup primitives Fuad Tabba
2026-06-19 13:31 ` Vincent Donnefort
2026-06-19 7:07 ` [PATCH v2 6/8] KVM: arm64: Minimise EL2's exposure of host VGIC state during world switch Fuad Tabba
2026-06-19 7:07 ` [PATCH v2 7/8] KVM: arm64: Add primitives to flush/sync the VGIC state at EL2 Fuad Tabba
2026-06-19 7:07 ` [PATCH v2 8/8] KVM: arm64: Implement lazy vCPU state sync for non-protected guests Fuad Tabba
2026-06-19 13:12 ` Vincent Donnefort
2026-06-19 16:41 ` Fuad Tabba
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