On Tue, Jan 8, 2019 at 12:26 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 04/01/19 09:54, lantianyu1986@xxxxxxxxx wrote:
> > rmap_head = __gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
> > PT_PAGE_TABLE_LEVEL, slot);
> > - __rmap_write_protect(kvm, rmap_head, false);
> > + flush |= __rmap_write_protect(kvm, rmap_head, false);
> >
> > /* clear the first set bit */
> > mask &= mask - 1;
> > }
> > +
> > + if (flush && kvm_available_flush_tlb_with_range()) {
> > + kvm_flush_remote_tlbs_with_address(kvm,
> > + slot->base_gfn + gfn_offset,
> > + hweight_long(mask));
>
> Mask is zero here, so this probably won't work.
>
> In addition, I suspect calling the hypercall once for every 64 pages is
> not very efficient. Passing a flush list into
> kvm_mmu_write_protect_pt_masked, and flushing in
> kvm_arch_mmu_enable_log_dirty_pt_masked, isn't efficient either because
> kvm_arch_mmu_enable_log_dirty_pt_masked is also called once per word.
>
Yes, this is not efficient.
> I don't have any good ideas, except for moving the whole
> kvm_clear_dirty_log_protect loop into architecture-specific code (which
> is not the direction we want---architectures should share more code, not
> less).
kvm_vm_ioctl_clear_dirty_log/get_dirty_log() is to get/clear dirty log with
memslot as unit. We may just flush tlbs of the affected memslot instead of
entire page table's when range flush is available.
>
> Paolo
>
> > + flush = false;
> > + }
> > +
>
--
Best regards
Tianyu Lan
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