Re: [PATCH v2 1/5] KVM: arm64: Add accessor for per-CPU state

Suzuki K Poulose
2024-03-25T14:31:51Z

Hi Marc

On 22/03/2024 17:09, Marc Zyngier wrote:
> In order to facilitate the introduction of new per-CPU state,
> add a new host_data_ptr() helped that hides some of the per-CPU
> verbosity, and make it easier to move that state around in the
> future.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> arch/arm64/include/asm/kvm_host.h | 37 +++++++++++++++++++++++
> arch/arm64/kvm/arm.c | 2 +-
> arch/arm64/kvm/hyp/include/hyp/debug-sr.h | 4 +--
> arch/arm64/kvm/hyp/include/hyp/switch.h | 8 ++---
> arch/arm64/kvm/hyp/nvhe/psci-relay.c | 2 +-
> arch/arm64/kvm/hyp/nvhe/setup.c | 3 +-
> arch/arm64/kvm/hyp/nvhe/switch.c | 4 +--
> arch/arm64/kvm/hyp/vhe/switch.c | 4 +--
> arch/arm64/kvm/hyp/vhe/sysreg-sr.c | 4 +--
> arch/arm64/kvm/pmu.c | 2 +-
> 10 files changed, 53 insertions(+), 17 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 6883963bbc3a..ca6ef663950d 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -530,6 +530,17 @@ struct kvm_cpu_context {
> u64 *vncr_array;
> };
>
> +/*
> + * This structure is instantiated on a per-CPU basis, and contains
> + * data that is:
> + *
> + * - tied to a single physical CPU, and
> + * - either have a lifetime that does not extend past vcpu_put()
> + * - or is an invariant for the lifetime of the system
> + *
> + * Use host_data_ptr(field) as a way to access a pointer to such a
> + * field.
> + */
> struct kvm_host_data {
> struct kvm_cpu_context host_ctxt;
> };
> @@ -1167,6 +1178,32 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>
> DECLARE_KVM_HYP_PER_CPU(struct kvm_host_data, kvm_host_data);
>
> +/*
> + * How we access per-CPU host data depends on the where we access it from,
> + * and the mode we're in:
> + *
> + * - VHE and nVHE hypervisor bits use their locally defined instance
> + *
> + * - the rest of the kernel use either the VHE or nVHE one, depending on
> + * the mode we're running in.
> + *
> + * Unless we're in protected mode, fully deprivileged, and the nVHE
> + * per-CPU stuff is exclusively accessible to the protected EL2 code.
> + * In this case, the EL1 code uses the *VHE* data as its private state
> + * (which makes sense in a way as there shouldn't be any shared state
> + * between the host and the hypervisor).

Does this mean we have a bug in cpu_hyp_init_context(), e.g. for a
hotplugged CPU and needs to be fixed for stable ?

Eitherways,

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

> + *
> + * Yes, this is all totally trivial. Shoot me now.
> + */
> +#if defined(__KVM_NVHE_HYPERVISOR__) || defined(__KVM_VHE_HYPERVISOR__)
> +#define host_data_ptr(f) (&this_cpu_ptr(&kvm_host_data)->f)
> +#else
> +#define host_data_ptr(f) \
> + (static_branch_unlikely(&kvm_protected_mode_initialized) ? \
> + &this_cpu_ptr(&kvm_host_data)->f : \
> + &this_cpu_ptr_hyp_sym(kvm_host_data)->f)
> +#endif
> +
> static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt)
> {
> /* The host's MPIDR is immutable, so let's set it up at boot time */
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 3dee5490eea9..a24287c3ba99 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1971,7 +1971,7 @@ static void cpu_set_hyp_vector(void)
>
> static void cpu_hyp_init_context(void)
> {
> - kvm_init_host_cpu_context(&this_cpu_ptr_hyp_sym(kvm_host_data)->host_ctxt);
> + kvm_init_host_cpu_context(host_data_ptr(host_ctxt));
>
> if (!is_kernel_in_hyp_mode())
> cpu_init_hyp_mode();
> diff --git a/arch/arm64/kvm/hyp/include/hyp/debug-sr.h b/arch/arm64/kvm/hyp/include/hyp/debug-sr.h
> index 961bbef104a6..eec0f8ccda56 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/debug-sr.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/debug-sr.h
> @@ -135,7 +135,7 @@ static inline void __debug_switch_to_guest_common(struct kvm_vcpu *vcpu)
> if (!vcpu_get_flag(vcpu, DEBUG_DIRTY))
> return;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
> guest_ctxt = &vcpu->arch.ctxt;
> host_dbg = &vcpu->arch.host_debug_state.regs;
> guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);
> @@ -154,7 +154,7 @@ static inline void __debug_switch_to_host_common(struct kvm_vcpu *vcpu)
> if (!vcpu_get_flag(vcpu, DEBUG_DIRTY))
> return;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
> guest_ctxt = &vcpu->arch.ctxt;
> host_dbg = &vcpu->arch.host_debug_state.regs;
> guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);
> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
> index e3fcf8c4d5b4..ae198b84ca01 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
> @@ -155,7 +155,7 @@ static inline bool cpu_has_amu(void)
>
> static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
> {
> - struct kvm_cpu_context *hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + struct kvm_cpu_context *hctxt = host_data_ptr(host_ctxt);
> struct kvm *kvm = kern_hyp_va(vcpu->kvm);
>
> CHECK_FGT_MASKS(HFGRTR_EL2);
> @@ -191,7 +191,7 @@ static inline void __activate_traps_hfgxtr(struct kvm_vcpu *vcpu)
>
> static inline void __deactivate_traps_hfgxtr(struct kvm_vcpu *vcpu)
> {
> - struct kvm_cpu_context *hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + struct kvm_cpu_context *hctxt = host_data_ptr(host_ctxt);
> struct kvm *kvm = kern_hyp_va(vcpu->kvm);
>
> if (!cpus_have_final_cap(ARM64_HAS_FGT))
> @@ -226,7 +226,7 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
>
> write_sysreg(0, pmselr_el0);
>
> - hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + hctxt = host_data_ptr(host_ctxt);
> ctxt_sys_reg(hctxt, PMUSERENR_EL0) = read_sysreg(pmuserenr_el0);
> write_sysreg(ARMV8_PMU_USERENR_MASK, pmuserenr_el0);
> vcpu_set_flag(vcpu, PMUSERENR_ON_CPU);
> @@ -260,7 +260,7 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
> if (kvm_arm_support_pmu_v3()) {
> struct kvm_cpu_context *hctxt;
>
> - hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + hctxt = host_data_ptr(host_ctxt);
> write_sysreg(ctxt_sys_reg(hctxt, PMUSERENR_EL0), pmuserenr_el0);
> vcpu_clear_flag(vcpu, PMUSERENR_ON_CPU);
> }
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> index d57bcb6ab94d..dfe8fe0f7eaf 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> @@ -205,7 +205,7 @@ asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
> struct psci_boot_args *boot_args;
> struct kvm_cpu_context *host_ctxt;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
>
> if (is_cpu_on)
> boot_args = this_cpu_ptr(&cpu_on_args);
> diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
> index bc58d1b515af..ae00dfa80801 100644
> --- a/arch/arm64/kvm/hyp/nvhe/setup.c
> +++ b/arch/arm64/kvm/hyp/nvhe/setup.c
> @@ -257,8 +257,7 @@ static int fix_hyp_pgtable_refcnt(void)
>
> void __noreturn __pkvm_init_finalise(void)
> {
> - struct kvm_host_data *host_data = this_cpu_ptr(&kvm_host_data);
> - struct kvm_cpu_context *host_ctxt = &host_data->host_ctxt;
> + struct kvm_cpu_context *host_ctxt = host_data_ptr(host_ctxt);
> unsigned long nr_pages, reserved_pages, pfn;
> int ret;
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
> index c50f8459e4fc..544a419b9a39 100644
> --- a/arch/arm64/kvm/hyp/nvhe/switch.c
> +++ b/arch/arm64/kvm/hyp/nvhe/switch.c
> @@ -264,7 +264,7 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> pmr_sync();
> }
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
> host_ctxt->__hyp_running_vcpu = vcpu;
> guest_ctxt = &vcpu->arch.ctxt;
>
> @@ -367,7 +367,7 @@ asmlinkage void __noreturn hyp_panic(void)
> struct kvm_cpu_context *host_ctxt;
> struct kvm_vcpu *vcpu;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
> vcpu = host_ctxt->__hyp_running_vcpu;
>
> if (vcpu) {
> diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
> index 1581df6aec87..14b7a6bc5909 100644
> --- a/arch/arm64/kvm/hyp/vhe/switch.c
> +++ b/arch/arm64/kvm/hyp/vhe/switch.c
> @@ -221,7 +221,7 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
> struct kvm_cpu_context *guest_ctxt;
> u64 exit_code;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
> host_ctxt->__hyp_running_vcpu = vcpu;
> guest_ctxt = &vcpu->arch.ctxt;
>
> @@ -306,7 +306,7 @@ static void __hyp_call_panic(u64 spsr, u64 elr, u64 par)
> struct kvm_cpu_context *host_ctxt;
> struct kvm_vcpu *vcpu;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
> vcpu = host_ctxt->__hyp_running_vcpu;
>
> __deactivate_traps(vcpu);
> diff --git a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
> index a8b9ea496706..e12bd7d6d2dc 100644
> --- a/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/vhe/sysreg-sr.c
> @@ -67,7 +67,7 @@ void __vcpu_load_switch_sysregs(struct kvm_vcpu *vcpu)
> struct kvm_cpu_context *guest_ctxt = &vcpu->arch.ctxt;
> struct kvm_cpu_context *host_ctxt;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
> __sysreg_save_user_state(host_ctxt);
>
> /*
> @@ -110,7 +110,7 @@ void __vcpu_put_switch_sysregs(struct kvm_vcpu *vcpu)
> struct kvm_cpu_context *guest_ctxt = &vcpu->arch.ctxt;
> struct kvm_cpu_context *host_ctxt;
>
> - host_ctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + host_ctxt = host_data_ptr(host_ctxt);
>
> __sysreg_save_el1_state(guest_ctxt);
> __sysreg_save_user_state(guest_ctxt);
> diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
> index a243934c5568..329819806096 100644
> --- a/arch/arm64/kvm/pmu.c
> +++ b/arch/arm64/kvm/pmu.c
> @@ -232,7 +232,7 @@ bool kvm_set_pmuserenr(u64 val)
> if (!vcpu || !vcpu_get_flag(vcpu, PMUSERENR_ON_CPU))
> return false;
>
> - hctxt = &this_cpu_ptr(&kvm_host_data)->host_ctxt;
> + hctxt = host_data_ptr(host_ctxt);
> ctxt_sys_reg(hctxt, PMUSERENR_EL0) = val;
> return true;
> }