On Thu, Jun 27, 2013 at 12:14:24PM +0300, Gleb Natapov wrote:
> On Thu, Jun 27, 2013 at 12:01:10PM +0300, Gleb Natapov wrote:
> > On Thu, Jun 27, 2013 at 11:29:00AM +0300, Gleb Natapov wrote:
> > > On Fri, Jun 07, 2013 at 04:51:26PM +0800, Xiao Guangrong wrote:
> > > > This patch tries to introduce a very simple and scale way to invalidate
> > > > all mmio sptes - it need not walk any shadow pages and hold mmu-lock
> > > >
> > > > KVM maintains a global mmio valid generation-number which is stored in
> > > > kvm->memslots.generation and every mmio spte stores the current global
> > > > generation-number into his available bits when it is created
> > > >
> > > > When KVM need zap all mmio sptes, it just simply increase the global
> > > > generation-number. When guests do mmio access, KVM intercepts a MMIO #PF
> > > > then it walks the shadow page table and get the mmio spte. If the
> > > > generation-number on the spte does not equal the global generation-number,
> > > > it will go to the normal #PF handler to update the mmio spte
> > > >
> > > > Since 19 bits are used to store generation-number on mmio spte, we zap all
> > > > mmio sptes when the number is round
> > > >
> > > So this commit makes Fedora 9 32 bit reboot during boot, Fedora 9 64
> > > fails too, but I haven't checked what happens exactly.
> > >
> > Something wrong with gfn calculation during mmio:
> >
> > qemu-system-x86-17003 [000] 3962.625103: handle_mmio_page_fault: addr:c00ba6c0 gfn 100000000ba access a92
> > qemu-system-x86-17003 [000] 3962.774862: handle_mmio_page_fault: addr:ffffb170 gfn 100000fee00 access a92
> >
> Hmm, so I wounder why get_mmio_spte_gfn() does not clear gen bits.
>
Hmm, something like patch below fixes it. Will test more.
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 1fd2c05..aec9c05 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -260,7 +260,8 @@ static bool is_mmio_spte(u64 spte)
static gfn_t get_mmio_spte_gfn(u64 spte)
{
- return (spte & ~shadow_mmio_mask) >> PAGE_SHIFT;
+ u64 mask = generation_mmio_spte_mask(MMIO_MAX_GEN) | shadow_mmio_mask;
+ return (spte & ~mask) >> PAGE_SHIFT;
}
static unsigned get_mmio_spte_access(u64 spte)
--
Gleb.
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