lkml.org 
[lkml]   [2012]   [Apr]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 08/13] KVM: MMU: fask check whether page is writable
    On Fri, Apr 06, 2012 at 01:54:52AM +0800, Xiao Guangrong wrote:
    > Hi Avi,
    >
    > Thanks very much for your review!
    >
    > Sorry for the delay reply since i was on vacation.
    >
    > On 04/01/2012 11:52 PM, Avi Kivity wrote:
    >
    > > On 03/29/2012 11:25 AM, Xiao Guangrong wrote:
    > >> Using PTE_LIST_WRITE_PROTECT bit in rmap store the write-protect status to
    > >> avoid unnecessary shadow page walking
    > >>
    > >> Also if no shadow page is indirect, the page is write-free
    > >>
    > >>
    > >> @@ -2262,6 +2291,9 @@ static int mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn,
    > >> }
    > >> if (need_unsync)
    > >> kvm_unsync_pages(vcpu, gfn);
    > >> +
    > >> + *rmap &= ~PTE_LIST_WRITE_PROTECT;
    > >> +
    > >>
    > >
    > > So what are the rules for PTE_LIST_WRITE_PROTECT? Is is a cache for the
    > > mmu_need_write_protect?
    > >
    > > I'd like to understand it, I guess it can be set while write protection
    > > is unneeded, and cleared on the next check?
    > >
    >
    >
    > Yes, it is used as a cache for mmu_need_write_protect.
    >
    > When the gfn is protected by sync sp or read-only host page we set this bit,
    > and it is be cleared when the sp become unsync or host page becomes writable.

    Wouldnt dropping support for shadow entirely make it much simpler?

    The idea to handle RO->RW without mmu_lock is very neat, but the
    complexity with shadow is horrible.




    \
     
     \ /
      Last update: 2012-04-13 01:43    [W:0.020 / U:31.800 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site