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Date: Tue, 24 Nov 2020 15:08:59 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: David Brazdil <dbrazdil@...gle.com>
Cc: kvmarm <kvmarm@...ts.cs.columbia.edu>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Marc Zyngier <maz@...nel.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>,
Mark Rutland <mark.rutland@....com>,
Andrew Scull <ascull@...gle.com>,
Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [RFC PATCH 6/6] kvm: arm64: Remove hyp_symbol_addr
On Thu, 19 Nov 2020 at 17:26, David Brazdil <dbrazdil@...gle.com> wrote:
>
> The helper was used to force PC-relative addressing in hyp code because
> absolute addressing via constant-pools used to generate kernel VAs. This
> was cumbersome and required programmers to remember to use the helper
> whenever they wanted to take a pointer.
>
> Now that hyp relocations are fixed up, there is no need for the helper
> any logner. Remove it.
>
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>
Acked-by: Ard Biesheuvel <ardb@...nel.org>
> ---
> arch/arm64/include/asm/kvm_asm.h | 20 --------------------
> arch/arm64/kvm/hyp/include/hyp/switch.h | 4 ++--
> arch/arm64/kvm/hyp/nvhe/hyp-smp.c | 4 ++--
> arch/arm64/kvm/hyp/nvhe/psci-relay.c | 4 ++--
> arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c | 2 +-
> 5 files changed, 7 insertions(+), 27 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> index 1a86581e581e..1961d23c0c40 100644
> --- a/arch/arm64/include/asm/kvm_asm.h
> +++ b/arch/arm64/include/asm/kvm_asm.h
> @@ -203,26 +203,6 @@ extern void __vgic_v3_init_lrs(void);
>
> extern u32 __kvm_get_mdcr_el2(void);
>
> -/*
> - * Obtain the PC-relative address of a kernel symbol
> - * s: symbol
> - *
> - * The goal of this macro is to return a symbol's address based on a
> - * PC-relative computation, as opposed to a loading the VA from a
> - * constant pool or something similar. This works well for HYP, as an
> - * absolute VA is guaranteed to be wrong. Only use this if trying to
> - * obtain the address of a symbol (i.e. not something you obtained by
> - * following a pointer).
> - */
> -#define hyp_symbol_addr(s) \
> - ({ \
> - typeof(s) *addr; \
> - asm("adrp %0, %1\n" \
> - "add %0, %0, :lo12:%1\n" \
> - : "=r" (addr) : "S" (&s)); \
> - addr; \
> - })
> -
> #define __KVM_EXTABLE(from, to) \
> " .pushsection __kvm_ex_table, \"a\"\n" \
> " .align 3\n" \
> diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
> index 84473574c2e7..54f4860cd87c 100644
> --- a/arch/arm64/kvm/hyp/include/hyp/switch.h
> +++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
> @@ -505,8 +505,8 @@ static inline void __kvm_unexpected_el2_exception(void)
> struct exception_table_entry *entry, *end;
> unsigned long elr_el2 = read_sysreg(elr_el2);
>
> - entry = hyp_symbol_addr(__start___kvm_ex_table);
> - end = hyp_symbol_addr(__stop___kvm_ex_table);
> + entry = &__start___kvm_ex_table;
> + end = &__stop___kvm_ex_table;
>
> while (entry < end) {
> addr = (unsigned long)&entry->insn + entry->insn;
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-smp.c b/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
> index ceb427aabb91..6870d9f3d4b7 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-smp.c
> @@ -33,8 +33,8 @@ unsigned long __hyp_per_cpu_offset(unsigned int cpu)
> if (cpu >= ARRAY_SIZE(kvm_arm_hyp_percpu_base))
> hyp_panic();
>
> - cpu_base_array = (unsigned long*)hyp_symbol_addr(kvm_arm_hyp_percpu_base);
> + cpu_base_array = (unsigned long*)(&kvm_arm_hyp_percpu_base[0]);
> this_cpu_base = kern_hyp_va(cpu_base_array[cpu]);
> - elf_base = (unsigned long)hyp_symbol_addr(__per_cpu_start);
> + elf_base = (unsigned long)&__per_cpu_start;
> return this_cpu_base - elf_base;
> }
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> index 313ef42f0eab..f64380a49a72 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> @@ -147,7 +147,7 @@ static int psci_cpu_suspend(u64 func_id, struct kvm_cpu_context *host_ctxt)
> * point if it is a deep sleep state.
> */
> ret = psci_call(func_id, power_state,
> - __hyp_pa(hyp_symbol_addr(__kvm_hyp_cpu_entry)),
> + __hyp_pa(__kvm_hyp_cpu_entry),
> __hyp_pa(cpu_params));
>
> release_reset_state(cpu_state);
> @@ -182,7 +182,7 @@ static int psci_cpu_on(u64 func_id, struct kvm_cpu_context *host_ctxt)
> return PSCI_RET_ALREADY_ON;
>
> ret = psci_call(func_id, mpidr,
> - __hyp_pa(hyp_symbol_addr(__kvm_hyp_cpu_entry)),
> + __hyp_pa(__kvm_hyp_cpu_entry),
> __hyp_pa(cpu_params));
>
> /*
> diff --git a/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c b/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c
> index 8f0585640241..87a54375bd6e 100644
> --- a/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c
> +++ b/arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c
> @@ -64,7 +64,7 @@ int __vgic_v2_perform_cpuif_access(struct kvm_vcpu *vcpu)
> }
>
> rd = kvm_vcpu_dabt_get_rd(vcpu);
> - addr = hyp_symbol_addr(kvm_vgic_global_state)->vcpu_hyp_va;
> + addr = kvm_vgic_global_state.vcpu_hyp_va;
> addr += fault_ipa - vgic->vgic_cpu_base;
>
> if (kvm_vcpu_dabt_iswrite(vcpu)) {
> --
> 2.29.2.299.gdc1121823c-goog
>
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