Re: [PATCH v4 2/6] KVM: arm64: Implement __kvm_tlb_flush_vmid_range()

[Raghavendra Rao Ananta]

On Mon, May 29, 2023 at 6:54 AM Marc Zyngier <maz@xxxxxxxxxx> wrote:
>
> On Fri, 19 May 2023 01:52:27 +0100,
> Raghavendra Rao Ananta <rananta@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >  arch/arm64/include/asm/kvm_asm.h   |  3 +++
> >  arch/arm64/kvm/hyp/nvhe/hyp-main.c | 11 +++++++++
> >  arch/arm64/kvm/hyp/nvhe/tlb.c      | 39 ++++++++++++++++++++++++++++++
> >  arch/arm64/kvm/hyp/vhe/tlb.c       | 35 +++++++++++++++++++++++++++
> >  4 files changed, 88 insertions(+)
> >
> > diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
> > index 43c3bc0f9544d..33352d9399e32 100644
> > --- a/arch/arm64/include/asm/kvm_asm.h
> > +++ b/arch/arm64/include/asm/kvm_asm.h
> > @@ -79,6 +79,7 @@ enum __kvm_host_smccc_func {
> >       __KVM_HOST_SMCCC_FUNC___pkvm_init_vm,
> >       __KVM_HOST_SMCCC_FUNC___pkvm_init_vcpu,
> >       __KVM_HOST_SMCCC_FUNC___pkvm_teardown_vm,
> > +     __KVM_HOST_SMCCC_FUNC___kvm_tlb_flush_vmid_range,
>
> nit: please keep this close to the other TLB operations.
>
Sure, I'll reorder this.

> >  };
> >
> >  #define DECLARE_KVM_VHE_SYM(sym)     extern char sym[]
> > @@ -225,6 +226,8 @@ extern void __kvm_flush_vm_context(void);
> >  extern void __kvm_flush_cpu_context(struct kvm_s2_mmu *mmu);
> >  extern void __kvm_tlb_flush_vmid_ipa(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, phys_addr_t end);
> >  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 728e01d4536b0..81d30737dc7c9 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> > @@ -125,6 +125,16 @@ static void handle___kvm_tlb_flush_vmid_ipa(struct kvm_cpu_context *host_ctxt)
> >       __kvm_tlb_flush_vmid_ipa(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(phys_addr_t, end, host_ctxt, 3);
> > +
> > +     __kvm_tlb_flush_vmid_range(kern_hyp_va(mmu), start, end);
> > +}
> > +
> >  static void handle___kvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt)
> >  {
> >       DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1);
> > @@ -315,6 +325,7 @@ static const hcall_t host_hcall[] = {
> >       HANDLE_FUNC(__kvm_vcpu_run),
> >       HANDLE_FUNC(__kvm_flush_vm_context),
> >       HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa),
> > +     HANDLE_FUNC(__kvm_tlb_flush_vmid_range),
> >       HANDLE_FUNC(__kvm_tlb_flush_vmid),
> >       HANDLE_FUNC(__kvm_flush_cpu_context),
> >       HANDLE_FUNC(__kvm_timer_set_cntvoff),
> > diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c b/arch/arm64/kvm/hyp/nvhe/tlb.c
> > index 978179133f4b9..d4ea549c4b5c4 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/tlb.c
> > +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c
> > @@ -130,6 +130,45 @@ void __kvm_tlb_flush_vmid_ipa(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, phys_addr_t end)
> > +{
> > +     struct tlb_inv_context cxt;
> > +     unsigned long pages, 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);
> > +     end = round_up(end, stride);
> > +     pages = (end - start) >> PAGE_SHIFT;
> > +
> > +     if (!system_supports_tlb_range() || pages >= MAX_TLBI_RANGE_PAGES) {
> > +             __kvm_tlb_flush_vmid(mmu);
> > +             return;
>
> Why do we give up on "pages >= MAX_TLBI_RANGE_PAGES"? I see no
> rationale for it in the patch. My understanding is that this is the
> maximum representable as a range, in which case this is a programming
> error.
>
> Or are you *on purpose* making the two equivalent?
>
Yes basically, I was trying to align the logic with what we have for
__flush_tlb_range(). But, if you feel that it's mostly caused by a
programming error, do we want to not do any flush at all?

Thank you.

Raghavendra
> Thanks,
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.