Re: [PATCH 2/2] kvm, ept: remove the default write bit

[Avi Kivity]

On 06/11/2010 10:50 PM, Marcelo Tosatti wrote:
> On Fri, Jun 11, 2010 at 07:30:50PM +0800, Lai Jiangshan wrote:
>    
> > When ept enabled, current code set shadow_base_present_pte
> > including the write bit, thus all pte entries have
> > writabe bit, and it means guest os can always
> > write to any mapped page (even VMM maps RO pages for
> > the guest.)
> >
> > We always use get_user_pages(write=1), so this bad code does not
> > cause any bad result currently.
> >
> > But it is really bad, so fix it, and we will use RO pages future.
> >
> > We will set writabe bit when it is really writable (determined by
> > the parameters of the set_spte())
> >
> > Signed-off-by: Lai Jiangshan<laijs@xxxxxxxxxxxxxx>
> > ---
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index fdb18cf..c7565ea 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -4365,8 +4365,7 @@ static int __init vmx_init(void)
> >
> >   	if (enable_ept) {
> >   		bypass_guest_pf = 0;
> > -		kvm_mmu_set_base_ptes(VMX_EPT_READABLE_MASK |
> > -			VMX_EPT_WRITABLE_MASK);
> > +		kvm_mmu_set_base_ptes(VMX_EPT_READABLE_MASK);
> >   		kvm_mmu_set_mask_ptes(0ull, 0ull, 0ull, 0ull,
> >   				VMX_EPT_EXECUTABLE_MASK);
> >   		kvm_enable_tdp();
> >      
> You can remove the call to kvm_mmu_set_base_ptes entirely, because
> VMX_EPT_READABLE_MASK == PT_PRESENT_MASK.
>    

We can leave that to a later patch which removes kvm_mmu_set_base_ptes() 
entirely.

--
error compiling committee.c: too many arguments to function

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