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

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Date:	Fri, 25 Jan 2013 12:59:12 +0900
From:	Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>
To:	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>
Cc:	Alex Williamson <alex.williamson@...hat.com>, gleb@...hat.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] kvm: IOMMU read-only mapping support

On Fri, 25 Jan 2013 11:28:40 +0800
Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com> wrote:

> > I think I can naturally update my patch after this gets merged.
> > 
> 
> Please wait.

The patch I mentioned above won't change anything.  Just cleans up
set_memory_region().  The only possible change which we discussed
before was whether we call iommu_map() on a flags change.

> 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.

> 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
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