On Fri, 19 Mar 2021 16:17:07 +0000,
Yoan Picchi <yoan.picchi@xxxxxxx> wrote:
>
> Add some counter for when a dpage get invalidated. The counter isn't
> in the function that actually do it though because it doesn't have
> either a kvm or vcpu argument, so we would have no way to access the
> counters. For this reason, the counter have been added to the calling
> functions instead.
>
> Signed-off-by: Yoan Picchi <yoan.picchi@xxxxxxx>
> ---
> arch/arm64/include/asm/kvm_host.h | 1 +
> arch/arm64/kvm/guest.c | 1 +
> arch/arm64/kvm/mmu.c | 5 ++++-
> 3 files changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 863603285..3609aa89d 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -547,6 +547,7 @@ static inline bool __vcpu_write_sys_reg_to_cpu(u64 val, int reg)
>
> struct kvm_vm_stat {
> ulong remote_tlb_flush;
> + ulong cached_page_invalidated;
> };
>
> struct kvm_vcpu_stat {
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 1029976ca..f6b1f0b63 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -41,6 +41,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
> VCPU_STAT("regular_page_mapped", regular_page_mapped),
> VCPU_STAT("huge_page_mapped", huge_page_mapped),
> VM_STAT("remote_tlb_flush", remote_tlb_flush),
> + VM_STAT("cached_page_invalidated", cached_page_invalidated),
> VCPU_STAT("exits", exits),
> VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),
> VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 55d7fe63b..d6ddf5ab8 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -893,8 +893,10 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> if (writable)
> prot |= KVM_PGTABLE_PROT_W;
>
> - if (fault_status != FSC_PERM && !device)
> + if (fault_status != FSC_PERM && !device) {
> clean_dcache_guest_page(pfn, vma_pagesize);
> + kvm->stat.cached_page_invalidated++;
> + }
>
> if (exec_fault) {
> prot |= KVM_PGTABLE_PROT_X;
> @@ -1166,6 +1168,7 @@ int kvm_set_spte_hva(struct kvm *kvm, unsigned long hva, pte_t pte)
> * just like a translation fault and clean the cache to the PoC.
> */
> clean_dcache_guest_page(pfn, PAGE_SIZE);
> + kvm->stat.cached_page_invalidated++;
> handle_hva_to_gpa(kvm, hva, end, &kvm_set_spte_handler, &pfn);
> return 0;
> }
Given that PoC flushing is only done on translation fault, what are
the odds that this would report a different number than that of
translation faults (assuming it was actually implemented)?
It is also interesting that you attribute the same cost to flushing a
4kB page or a 1GB block. And what does this mean when either FWB or
IDC are available?
M.
--
Without deviation from the norm, progress is not possible.
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