Re: [PATCH v2 3/10] KVM: MMU: fix direct sp's access corruptted

From: Avi Kivity
Date: Mon Jun 28 2010 - 07:13:32 EST

On 06/28/2010 01:02 PM, Xiao Guangrong wrote:

Avi Kivity wrote:

Instead of adding a new bit, can you encode the protection in the direct
sp's access bits? So we'll have one sp for read-only or
writeable-but-not-dirty small pages, and another sp for
writeable-and-dirty small pages.

It looks like it can't solve all problems, it fix the access corrupted,
but will cause D bit losed:

mapping A and mapping B both are writable-and-dirty, when mapping A write
#PF occurs, the mapping is writable, then we can't set B's D bit anymore.

If B is writeable-and-dirty, then it's D bit is already set, and we don't need to do anything.

If B is writeable-and-clean, then we'll have an spte pointing to a read-only sp, so we'll get a write fault on access and an opportunity to set the D bit.

Anyway, i think we should re-intall the mapping when the state is changed. :-(

When the gpte is changed from read-only to writeable or from clean to dirty, we need to update the spte, yes. But that's true for other sptes as well, not just large gptes.

error compiling committee.c: too many arguments to function

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