Re: [PATCH 0/2] kvm: IOMMU read-only mapping support

Takuya Yoshikawa
2013-01-25T04:27:58Z

On Fri, 25 Jan 2013 12:59:12 +0900
Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp> wrote:

> > The commit c972f3b1 changed the write-protect behaviour - it does
> > wirte-protection only when dirty flag is set.
> > [ I did not see this commit when we discussed the problem before. ]
>
> I'll look at the commit later, after the lunch break.

I've done!

So we need to do:

if (npages && (GET_DIRTY || RDONLY))
write protect

About sync_page, I'm not sure what is the best fix.

Takuya

>
> > Further more, i notice that write-protect is not enough, when do sync
> > shadow page:
> >
> > FNAME(sync_page):
> >
> > host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE;
> >
> > set_spte(vcpu, &sp->spt[i], pte_access,
> > PT_PAGE_TABLE_LEVEL, gfn,
> > spte_to_pfn(sp->spt[i]), true, false,
> > host_writable);
> >
> > It sets spte based on the old value that means the readonly flag check
> > is missed. We need to call kvm_arch_flush_shadow_all under this case.
>
> So the change needed will be in arch/x86.
> in arch_commit_* one.
>
> Right?
>
> Note: I'm not touching arch_* memory slot APIs now because ARM KVM
> is coming now. So no problem, the flags will be passed as before.
>
> Takuya

--
Takuya Yoshikawa <yoshikawa_takuya_b1@lab.ntt.co.jp>