Re: [RFC PATCH 4/6] kvm: arm64: Remove patching of fn pointers in hyp

From: Ard Biesheuvel <ardb@kernel.org>
To: David Brazdil <dbrazdil@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Android Kernel Team <kernel-team@android.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	James Morse <james.morse@arm.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	kvmarm <kvmarm@lists.cs.columbia.edu>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Andrew Scull <ascull@google.com>
Subject: Re: [RFC PATCH 4/6] kvm: arm64: Remove patching of fn pointers in hyp
Date: Tue, 24 Nov 2020 15:03:14 +0100	[thread overview]
Message-ID: <CAMj1kXF9c6FXejpesh1E7ivgOm-aeUnG8enUhcyHDDjg8EgVJQ@mail.gmail.com> (raw)
In-Reply-To: <20201119162543.78001-5-dbrazdil@google.com>

On Thu, 19 Nov 2020 at 17:25, David Brazdil <dbrazdil@google.com> wrote:
>
> Taking a function pointer will now generate a R_AARCH64_RELATIVE that is
> fixed up at early boot. Remove the alternative-based mechanism for
> converting the address from a kernel VA.
>
> Signed-off-by: David Brazdil <dbrazdil@google.com>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

> ---
>  arch/arm64/include/asm/kvm_mmu.h   | 18 ------------------
>  arch/arm64/kernel/image-vars.h     |  1 -
>  arch/arm64/kvm/hyp/nvhe/hyp-main.c | 11 ++++-------
>  arch/arm64/kvm/va_layout.c         |  6 ------
>  4 files changed, 4 insertions(+), 32 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> index e5226f7e4732..8cb8974ec9cc 100644
> --- a/arch/arm64/include/asm/kvm_mmu.h
> +++ b/arch/arm64/include/asm/kvm_mmu.h
> @@ -121,24 +121,6 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v)
>
>  #define kern_hyp_va(v)         ((typeof(v))(__kern_hyp_va((unsigned long)(v))))
>
> -static __always_inline unsigned long __kimg_hyp_va(unsigned long v)
> -{
> -       unsigned long offset;
> -
> -       asm volatile(ALTERNATIVE_CB("movz %0, #0\n"
> -                                   "movk %0, #0, lsl #16\n"
> -                                   "movk %0, #0, lsl #32\n"
> -                                   "movk %0, #0, lsl #48\n",
> -                                   kvm_update_kimg_phys_offset)
> -                    : "=r" (offset));
> -
> -       return __kern_hyp_va((v - offset) | PAGE_OFFSET);
> -}
> -
> -#define kimg_fn_hyp_va(v)      ((typeof(*v))(__kimg_hyp_va((unsigned long)(v))))
> -
> -#define kimg_fn_ptr(x) (typeof(x) **)(x)
> -
>  /*
>   * We currently support using a VM-specified IPA size. For backward
>   * compatibility, the default IPA size is fixed to 40bits.
> diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
> index 8539f34d7538..6379721236cf 100644
> --- a/arch/arm64/kernel/image-vars.h
> +++ b/arch/arm64/kernel/image-vars.h
> @@ -64,7 +64,6 @@ __efistub__ctype              = _ctype;
>  /* Alternative callbacks for init-time patching of nVHE hyp code. */
>  KVM_NVHE_ALIAS(kvm_patch_vector_branch);
>  KVM_NVHE_ALIAS(kvm_update_va_mask);
> -KVM_NVHE_ALIAS(kvm_update_kimg_phys_offset);
>  KVM_NVHE_ALIAS(kvm_get_kimage_voffset);
>
>  /* Global kernel state accessed by nVHE hyp code. */
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index b3db5f4eea27..7998eff5f0a2 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -110,9 +110,9 @@ static void handle___vgic_v3_restore_aprs(struct kvm_cpu_context *host_ctxt)
>
>  typedef void (*hcall_t)(struct kvm_cpu_context *);
>
> -#define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = kimg_fn_ptr(handle_##x)
> +#define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = (hcall_t)handle_##x
>
> -static const hcall_t *host_hcall[] = {
> +static const hcall_t host_hcall[] = {
>         HANDLE_FUNC(__kvm_vcpu_run),
>         HANDLE_FUNC(__kvm_flush_vm_context),
>         HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa),
> @@ -132,7 +132,6 @@ static const hcall_t *host_hcall[] = {
>  static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
>  {
>         DECLARE_REG(unsigned long, id, host_ctxt, 0);
> -       const hcall_t *kfn;
>         hcall_t hfn;
>
>         id -= KVM_HOST_SMCCC_ID(0);
> @@ -140,13 +139,11 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
>         if (unlikely(id >= ARRAY_SIZE(host_hcall)))
>                 goto inval;
>
> -       kfn = host_hcall[id];
> -       if (unlikely(!kfn))
> +       hfn = host_hcall[id];
> +       if (unlikely(!hfn))
>                 goto inval;
>
>         cpu_reg(host_ctxt, 0) = SMCCC_RET_SUCCESS;
> -
> -       hfn = kimg_fn_hyp_va(kfn);
>         hfn(host_ctxt);
>
>         return;
> diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
> index 7f45a98eacfd..0494315f71f2 100644
> --- a/arch/arm64/kvm/va_layout.c
> +++ b/arch/arm64/kvm/va_layout.c
> @@ -373,12 +373,6 @@ static void generate_mov_q(u64 val, __le32 *origptr, __le32 *updptr, int nr_inst
>         *updptr++ = cpu_to_le32(insn);
>  }
>
> -void kvm_update_kimg_phys_offset(struct alt_instr *alt,
> -                                __le32 *origptr, __le32 *updptr, int nr_inst)
> -{
> -       generate_mov_q(kimage_voffset + PHYS_OFFSET, origptr, updptr, nr_inst);
> -}
> -
>  void kvm_get_kimage_voffset(struct alt_instr *alt,
>                             __le32 *origptr, __le32 *updptr, int nr_inst)
>  {
> --
> 2.29.2.299.gdc1121823c-goog
>

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