Re: [PATCH v7 08/12] KVM: arm64: Define kvm_tlb_flush_vmid_range()

From: Marc Zyngier <maz@kernel.org>
To: Raghavendra Rao Ananta <rananta@google.com>
Cc: Oliver Upton <oliver.upton@linux.dev>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Sean Christopherson <seanjc@google.com>,
	Huacai Chen <chenhuacai@kernel.org>,
	Zenghui Yu <yuzenghui@huawei.com>,
	Anup Patel <anup@brainfault.org>,
	Atish Patra <atishp@atishpatra.org>,
	Jing Zhang <jingzhangos@google.com>,
	Reiji Watanabe <reijiw@google.com>,
	Colton Lewis <coltonlewis@google.com>,
	David Matlack <dmatlack@google.com>,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	linux-mips@vger.kernel.org, kvm-riscv@lists.infradead.org,
	linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, Gavin Shan <gshan@redhat.com>,
	Shaoqin Huang <shahuang@redhat.com>
Subject: Re: [PATCH v7 08/12] KVM: arm64: Define kvm_tlb_flush_vmid_range()
Date: Thu, 27 Jul 2023 13:47:06 +0100	[thread overview]
Message-ID: <87o7jxr06t.wl-maz@kernel.org> (raw)
In-Reply-To: <20230722022251.3446223-9-rananta@google.com>

On Sat, 22 Jul 2023 03:22:47 +0100,
Raghavendra Rao Ananta <rananta@google.com> wrote:
> 
> Implement the helper kvm_tlb_flush_vmid_range() that acts
> as a wrapper for range-based TLB invalidations. For the
> given VMID, use the range-based TLBI instructions to do
> the job or fallback to invalidating all the TLB entries.
> 
> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
> Reviewed-by: Gavin Shan <gshan@redhat.com>
> Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
> ---
>  arch/arm64/include/asm/kvm_pgtable.h | 10 ++++++++++
>  arch/arm64/kvm/hyp/pgtable.c         | 20 ++++++++++++++++++++
>  2 files changed, 30 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> index 8294a9a7e566..5e8b1ff07854 100644
> --- a/arch/arm64/include/asm/kvm_pgtable.h
> +++ b/arch/arm64/include/asm/kvm_pgtable.h
> @@ -754,4 +754,14 @@ enum kvm_pgtable_prot kvm_pgtable_stage2_pte_prot(kvm_pte_t pte);
>   *	   kvm_pgtable_prot format.
>   */
>  enum kvm_pgtable_prot kvm_pgtable_hyp_pte_prot(kvm_pte_t pte);
> +
> +/**
> + * kvm_tlb_flush_vmid_range() - Invalidate/flush a range of TLB entries
> + *
> + * @mmu:	Stage-2 KVM MMU struct
> + * @addr:	The base Intermediate physical address from which to invalidate
> + * @size:	Size of the range from the base to invalidate
> + */
> +void kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu,
> +				phys_addr_t addr, size_t size);
>  #endif	/* __ARM64_KVM_PGTABLE_H__ */
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index aa740a974e02..5d14d5d5819a 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -670,6 +670,26 @@ static bool stage2_has_fwb(struct kvm_pgtable *pgt)
>  	return !(pgt->flags & KVM_PGTABLE_S2_NOFWB);
>  }
>  
> +void kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu,
> +				phys_addr_t addr, size_t size)
> +{
> +	unsigned long pages, inval_pages;
> +
> +	if (!system_supports_tlb_range()) {
> +		kvm_call_hyp(__kvm_tlb_flush_vmid, mmu);
> +		return;
> +	}
> +
> +	pages = size >> PAGE_SHIFT;
> +	while (pages > 0) {
> +		inval_pages = min(pages, MAX_TLBI_RANGE_PAGES);
> +		kvm_call_hyp(__kvm_tlb_flush_vmid_range, mmu, addr, inval_pages);
> +
> +		addr += inval_pages << PAGE_SHIFT;
> +		pages -= inval_pages;
> +	}
> +}
> +

This really shouldn't live in pgtable.c. This code gets linked into
the EL2 object. What do you think happens if, for some reason, this
gets called *from EL2*?

Furthermore, this doesn't deal with page tables at all. Why isn't
mmu.c a convenient place for it, as an integral part of
kvm_arch_flush_remote_tlbs_range?

	M.

-- 
Without deviation from the norm, progress is not possible.

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