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Message-ID: <87lfes5f54.wl-maz@kernel.org>
Date: Mon, 23 Nov 2020 14:20:07 +0000
From: Marc Zyngier <maz@...nel.org>
To: David Brazdil <dbrazdil@...gle.com>
Cc: kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, James Morse <james.morse@....com>,
Julien Thierry <julien.thierry.kdev@...il.com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Dennis Zhou <dennis@...nel.org>,
Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
Mark Rutland <mark.rutland@....com>,
Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Quentin Perret <qperret@...gle.com>,
Andrew Scull <ascull@...gle.com>,
Andrew Walbran <qwandor@...gle.com>, kernel-team@...roid.com
Subject: Re: [PATCH v2 06/24] kvm: arm64: Move hyp-init params to a per-CPU struct
On Mon, 16 Nov 2020 20:43:00 +0000,
David Brazdil <dbrazdil@...gle.com> wrote:
>
> Once we start initializing KVM on newly booted cores before the rest of
> the kernel, parameters to __do_hyp_init will need to be provided by EL2
> rather than EL1. At that point it will not be possible to pass its four
> arguments directly because PSCI_CPU_ON only supports one context
> argument.
>
> Refactor __do_hyp_init to accept its parameters in a struct. This
> prepares the code for KVM booting cores as well as removes any limits on
> the number of __do_hyp_init arguments.
>
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>
> ---
> arch/arm64/include/asm/kvm_asm.h | 7 +++++++
> arch/arm64/include/asm/kvm_hyp.h | 4 ++++
> arch/arm64/kernel/asm-offsets.c | 4 ++++
> arch/arm64/kvm/arm.c | 26 ++++++++++++++------------
> arch/arm64/kvm/hyp/nvhe/hyp-init.S | 21 ++++++++++-----------
> arch/arm64/kvm/hyp/nvhe/hyp-main.c | 2 ++
> 6 files changed, 41 insertions(+), 23 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 54387ccd1ab2..01904e88cead 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -150,6 +150,13 @@ extern void *__vhe_undefined_symbol;
>
> #endif
>
> +struct kvm_nvhe_init_params {
> + unsigned long tpidr_el2;
> + unsigned long vector_hyp_va;
> + unsigned long stack_hyp_va;
> + phys_addr_t pgd_pa;
> +};
> +
> /* Translate a kernel address @ptr into its equivalent linear mapping */
> #define kvm_ksym_ref(ptr) \
> ({ \
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 6b664de5ec1f..a3289071f3d8 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -15,6 +15,10 @@
> DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
> DECLARE_PER_CPU(unsigned long, kvm_hyp_vector);
>
> +#ifdef __KVM_NVHE_HYPERVISOR__
> +DECLARE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
> +#endif
I'm not sure we should bother with this #ifdefery. Having the
declaration present at all times doesn't really hurt, since it is only
defined in the HYP code. Cutting down on the conditionals would
certainly help readability.
> +
> #define read_sysreg_elx(r,nvh,vh) \
> ({ \
> u64 reg; \
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 7d32fc959b1a..4435ad8be938 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -110,6 +110,10 @@ int main(void)
> DEFINE(CPU_APGAKEYLO_EL1, offsetof(struct kvm_cpu_context, sys_regs[APGAKEYLO_EL1]));
> DEFINE(HOST_CONTEXT_VCPU, offsetof(struct kvm_cpu_context, __hyp_running_vcpu));
> DEFINE(HOST_DATA_CONTEXT, offsetof(struct kvm_host_data, host_ctxt));
> + DEFINE(NVHE_INIT_TPIDR_EL2, offsetof(struct kvm_nvhe_init_params, tpidr_el2));
> + DEFINE(NVHE_INIT_VECTOR_HYP_VA, offsetof(struct kvm_nvhe_init_params, vector_hyp_va));
> + DEFINE(NVHE_INIT_STACK_HYP_VA, offsetof(struct kvm_nvhe_init_params, stack_hyp_va));
> + DEFINE(NVHE_INIT_PGD_PA, offsetof(struct kvm_nvhe_init_params, pgd_pa));
> #endif
> #ifdef CONFIG_CPU_PM
> DEFINE(CPU_CTX_SP, offsetof(struct cpu_suspend_ctx, sp));
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index c0ffb019ca8b..4838556920fb 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -50,6 +50,7 @@ DECLARE_KVM_HYP_PER_CPU(unsigned long, kvm_hyp_vector);
>
> static DEFINE_PER_CPU(unsigned long, kvm_arm_hyp_stack_page);
> unsigned long kvm_arm_hyp_percpu_base[NR_CPUS];
> +DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
>
> /* The VMID used in the VTTBR */
> static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
> @@ -1347,10 +1348,7 @@ static int kvm_map_vectors(void)
>
> static void cpu_init_hyp_mode(void)
> {
> - phys_addr_t pgd_ptr;
> - unsigned long hyp_stack_ptr;
> - unsigned long vector_ptr;
> - unsigned long tpidr_el2;
> + struct kvm_nvhe_init_params *params = this_cpu_ptr_nvhe_sym(kvm_init_params);
> struct arm_smccc_res res;
>
> /* Switch from the HYP stub to our own HYP init vector */
> @@ -1361,13 +1359,18 @@ static void cpu_init_hyp_mode(void)
> * kernel's mapping to the linear mapping, and store it in tpidr_el2
> * so that we can use adr_l to access per-cpu variables in EL2.
> */
> - tpidr_el2 = (unsigned long)this_cpu_ptr_nvhe_sym(__per_cpu_start) -
> - (unsigned long)kvm_ksym_ref(CHOOSE_NVHE_SYM(__per_cpu_start));
> + params->tpidr_el2 = (unsigned long)this_cpu_ptr_nvhe_sym(__per_cpu_start) -
> + (unsigned long)kvm_ksym_ref(CHOOSE_NVHE_SYM(__per_cpu_start));
>
> - pgd_ptr = kvm_mmu_get_httbr();
> - hyp_stack_ptr = __this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE;
> - hyp_stack_ptr = kern_hyp_va(hyp_stack_ptr);
> - vector_ptr = (unsigned long)kern_hyp_va(kvm_ksym_ref(__kvm_hyp_host_vector));
> + params->vector_hyp_va = (unsigned long)kern_hyp_va(kvm_ksym_ref(__kvm_hyp_host_vector));
> + params->stack_hyp_va = kern_hyp_va(__this_cpu_read(kvm_arm_hyp_stack_page) + PAGE_SIZE);
> + params->pgd_pa = kvm_mmu_get_httbr();
Note to self: rename this to kvm_mmu_get_hyp_pgd() (another AArch32-ism).
> +
> + /*
> + * Flush the init params from the data cache because the struct will
> + * be read while the MMU is off.
> + */
> + __flush_dcache_area(params, sizeof(*params));
nit: please use kvm_flush_dcache_to_poc(), as it clearly indicates to
which point we are flushing.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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