On Sat, Nov 12, 2022 at 08:17:08AM +0000, Ricardo Koller wrote:
> Breaking a huge-page block PTE into an equivalent table of smaller PTEs
> does not require using break-before-make (BBM) when FEAT_BBM level 2 is
> implemented. Add the respective check for eager page splitting and avoid
> using BBM.
>
> Also take care of possible Conflict aborts. According to the rules
> specified in the Arm ARM (DDI 0487H.a) section "Support levels for changing
> block size" D5.10.1, this can result in a Conflict abort. So, handle it by
> clearing all VM TLB entries.
>
> Signed-off-by: Ricardo Koller <ricar...@google.com>
I'd suggest adding the TLB conflict abort handler as a separate commit
prior to actually relaxing break-before-make requirements.
> ---
> arch/arm64/include/asm/esr.h | 1 +
> arch/arm64/include/asm/kvm_arm.h | 1 +
> arch/arm64/kvm/hyp/pgtable.c | 10 +++++++++-
> arch/arm64/kvm/mmu.c | 6 ++++++
> 4 files changed, 17 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
> index 15b34fbfca66..6f5b976396e7 100644
> --- a/arch/arm64/include/asm/esr.h
> +++ b/arch/arm64/include/asm/esr.h
> @@ -114,6 +114,7 @@
> #define ESR_ELx_FSC_ACCESS (0x08)
> #define ESR_ELx_FSC_FAULT (0x04)
> #define ESR_ELx_FSC_PERM (0x0C)
> +#define ESR_ELx_FSC_CONFLICT (0x30)
>
> /* ISS field definitions for Data Aborts */
> #define ESR_ELx_ISV_SHIFT (24)
> diff --git a/arch/arm64/include/asm/kvm_arm.h
> b/arch/arm64/include/asm/kvm_arm.h
> index 0df3fc3a0173..58e7cbe3c250 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -333,6 +333,7 @@
> #define FSC_SECC_TTW1 (0x1d)
> #define FSC_SECC_TTW2 (0x1e)
> #define FSC_SECC_TTW3 (0x1f)
> +#define FSC_CONFLICT ESR_ELx_FSC_CONFLICT
>
> /* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
> #define HPFAR_MASK (~UL(0xf))
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index 9c42eff6d42e..36b81df5687e 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -1267,6 +1267,11 @@ static int stage2_create_removed(kvm_pte_t *ptep, u64
> phys, u32 level,
> return __kvm_pgtable_visit(&data, mm_ops, ptep, level);
> }
>
> +static bool stage2_has_bbm_level2(void)
> +{
> + return cpus_have_const_cap(ARM64_HAS_STAGE2_BBM2);
> +}
> +
> struct stage2_split_data {
> struct kvm_s2_mmu *mmu;
> void *memcache;
> @@ -1308,7 +1313,10 @@ static int stage2_split_walker(const struct
> kvm_pgtable_visit_ctx *ctx,
> */
> WARN_ON(stage2_create_removed(&new, phys, level, attr, mc, mm_ops));
>
> - stage2_put_pte(ctx, data->mmu, mm_ops);
> + if (stage2_has_bbm_level2())
> + mm_ops->put_page(ctx->ptep);
> + else
> + stage2_put_pte(ctx, data->mmu, mm_ops);
>
> /*
> * Note, the contents of the page table are guaranteed to be made
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 8f26c65693a9..318f7b0aa20b 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1481,6 +1481,12 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
> return 1;
> }
>
> + /* Conflict abort? */
> + if (fault_status == FSC_CONFLICT) {
> + kvm_flush_remote_tlbs(vcpu->kvm);
You don't need to perfom a broadcasted invalidation in this case. A
local invalidation using the guest's VMID should suffice.
--
Thanks,
Oliver
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