linux-kernel - Re: [PATCH v7 07/12] KVM: arm64: Implement __kvm_tlb_flush_vmid

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Message-ID: <CAJHc60ztA7pNQVHbd1WPmPNkoEzZWarDmxnLxh=-5ZYo9CWw2g@mail.gmail.com>
Date:   Mon, 31 Jul 2023 10:45:01 -0700
From:   Raghavendra Rao Ananta <rananta@...gle.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Jing Zhang <jingzhangos@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
        linux-mips@...r.kernel.org, kvm-riscv@...ts.infradead.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Gavin Shan <gshan@...hat.com>
Subject: Re: [PATCH v7 07/12] KVM: arm64: Implement __kvm_tlb_flush_vmid_range()

On Thu, Jul 27, 2023 at 5:40 AM Marc Zyngier <maz@...nel.org> wrote:
>
> On Sat, 22 Jul 2023 03:22:46 +0100,
> Raghavendra Rao Ananta <rananta@...gle.com> wrote:
> >
> > Define  __kvm_tlb_flush_vmid_range() (for VHE and nVHE)
> > to flush a range of stage-2 page-tables using IPA in one go.
> > If the system supports FEAT_TLBIRANGE, the following patches
> > would conviniently replace global TLBI such as vmalls12e1is
> > in the map, unmap, and dirty-logging paths with ripas2e1is
> > instead.
> >
> > Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
> > Reviewed-by: Gavin Shan <gshan@...hat.com>
> > ---
> >  arch/arm64/include/asm/kvm_asm.h   |  3 +++
> >  arch/arm64/kvm/hyp/nvhe/hyp-main.c | 11 +++++++++++
> >  arch/arm64/kvm/hyp/nvhe/tlb.c      | 30 ++++++++++++++++++++++++++++++
> >  arch/arm64/kvm/hyp/vhe/tlb.c       | 27 +++++++++++++++++++++++++++
> >  4 files changed, 71 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> > index 7d170aaa2db4..2c27cb8cf442 100644
> > --- a/arch/arm64/include/asm/kvm_asm.h
> > +++ b/arch/arm64/include/asm/kvm_asm.h
> > @@ -70,6 +70,7 @@ enum __kvm_host_smccc_func {
> >       __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa,
> >       __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_ipa_nsh,
> >       __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid,
> > +     __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_range,
> >       __KVM_HOST_SMCCC_FUNC___kvm_flush_cpu_context,
> >       __KVM_HOST_SMCCC_FUNC___kvm_timer_set_cntvoff,
> >       __KVM_HOST_SMCCC_FUNC___vgic_v3_read_vmcr,
> > @@ -229,6 +230,8 @@ extern void __kvm_tlb_flush_vmid_ipa(struct kvm_s2_mmu *mmu, phys_addr_t ipa,
> >  extern void __kvm_tlb_flush_vmid_ipa_nsh(struct kvm_s2_mmu *mmu,
> >                                        phys_addr_t ipa,
> >                                        int level);
> > +extern void __kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu,
> > +                                     phys_addr_t start, unsigned long pages);
> >  extern void __kvm_tlb_flush_vmid(struct kvm_s2_mmu *mmu);
> >
> >  extern void __kvm_timer_set_cntvoff(u64 cntvoff);
> > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> > index a169c619db60..857d9bc04fd4 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> > @@ -135,6 +135,16 @@ static void handle___kvm_tlb_flush_vmid_ipa_nsh(struct kvm_cpu_context *host_ctx
> >       __kvm_tlb_flush_vmid_ipa_nsh(kern_hyp_va(mmu), ipa, level);
> >  }
> >
> > +static void
> > +handle___kvm_tlb_flush_vmid_range(struct kvm_cpu_context *host_ctxt)
> > +{
> > +     DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1);
> > +     DECLARE_REG(phys_addr_t, start, host_ctxt, 2);
> > +     DECLARE_REG(unsigned long, pages, host_ctxt, 3);
> > +
> > +     __kvm_tlb_flush_vmid_range(kern_hyp_va(mmu), start, pages);
> > +}
> > +
> >  static void handle___kvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt)
> >  {
> >       DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1);
> > @@ -327,6 +337,7 @@ static const hcall_t host_hcall[] = {
> >       HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa),
> >       HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa_nsh),
> >       HANDLE_FUNC(__kvm_tlb_flush_vmid),
> > +     HANDLE_FUNC(__kvm_tlb_flush_vmid_range),
> >       HANDLE_FUNC(__kvm_flush_cpu_context),
> >       HANDLE_FUNC(__kvm_timer_set_cntvoff),
> >       HANDLE_FUNC(__vgic_v3_read_vmcr),
> > diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c b/arch/arm64/kvm/hyp/nvhe/tlb.c
> > index b9991bbd8e3f..09347111c2cd 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/tlb.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c
> > @@ -182,6 +182,36 @@ void __kvm_tlb_flush_vmid_ipa_nsh(struct kvm_s2_mmu *mmu,
> >       __tlb_switch_to_host(&cxt);
> >  }
> >
> > +void __kvm_tlb_flush_vmid_range(struct kvm_s2_mmu *mmu,
> > +                             phys_addr_t start, unsigned long pages)
> > +{
> > +     struct tlb_inv_context cxt;
> > +     unsigned long stride;
> > +
> > +     /*
> > +      * Since the range of addresses may not be mapped at
> > +      * the same level, assume the worst case as PAGE_SIZE
> > +      */
> > +     stride = PAGE_SIZE;
> > +     start = round_down(start, stride);
> > +
> > +     /* Switch to requested VMID */
> > +     __tlb_switch_to_guest(mmu, &cxt, false);
> > +
> > +     __flush_tlb_range_op(ipas2e1is, start, pages, stride, 0, 0, false);
>
> I really think we need an abstraction here. All this ASID and user
> nonsense shouldn't appear here. Something such as
> __flush_s2_tlb_range_op(), which would pass the correct parameters
> that this code shouldn't have to worry about.
>
Yes, a simple wrapper would be nice. I'll implement this in v8.

> I'm also a bit concerned by the fact we completely lose the level
> here. This is a massive fast-path for the CPU, and we don't make use
> of it. It'd be worth thinking of how we can make use of it if at all
> possible...
>
Initial implementation of the series included the 'level', but had
some complexities [1], and so we had to get rid of it for things to at
least be correct.
But, we can think about it and include the 'level' as needed.

- Raghavendra

[1]: https://lore.kernel.org/all/ZCTjirkCgBkT65eP@linux.dev/

> > +
> > +     dsb(ish);
> > +     __tlbi(vmalle1is);
> > +     dsb(ish);
> > +     isb();
> > +
> > +     /* See the comment in __kvm_tlb_flush_vmid_ipa() */
> > +     if (icache_is_vpipt())
> > +             icache_inval_all_pou();
> > +
> > +     __tlb_switch_to_host(&cxt);
>
> Another thing is that it is high time that some of this call gets
> refactored. All these helpers are basically the same sequence, only
> differing by a couple of lines. Not something we need to do
> immediately, but eventually we'll have to bite the bullet.
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.