On Tue, Feb 09, 2021 at 08:46:42AM +0100, Paolo Bonzini wrote: > On 09/02/21 04:33, Yu Zhang wrote: > > On Mon, Feb 08, 2021 at 05:47:22PM +0100, Paolo Bonzini wrote: > > > On 08/02/21 14:49, Yu Zhang wrote: > > > > On Mon, Feb 08, 2021 at 12:36:57PM +0100, Paolo Bonzini wrote: > > > > > On 07/02/21 13:22, Yu Zhang wrote: > > > > > > In shadow page table, only leaf SPs may be marked as unsync. > > > > > > And for non-leaf SPs, we use unsync_children to keep the number > > > > > > of the unsynced children. In kvm_mmu_sync_root(), sp->unsync > > > > > > shall always be zero for the root SP, , hence no need to check > > > > > > it. Instead, a warning inside mmu_sync_children() is added, in > > > > > > case someone incorrectly used it. > > > > > > > > > > > > Also, clarify the mmu_need_write_protect(), by moving the warning > > > > > > into kvm_unsync_page(). > > > > > > > > > > > > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > > > > > > Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> > > > > > > > > > > This should really be more of a Co-developed-by, and there are a couple > > > > > adjustments that could be made in the commit message. I've queued the patch > > > > > and I'll fix it up later. > > > > > > > > Indeed. Thanks for the remind, and I'll pay attention in the future. :) > > > > > > Also: > > > > > > arch/x86/kvm/mmu/mmu.c: In function ‘mmu_sync_children’: > > > arch/x86/kvm/mmu/mmu.c:2002:17: error: ‘sp’ is used uninitialized in this > > > function [-Werror=uninitialized] > > > WARN_ON_ONCE(sp->unsync); > > > > Oops. This is wrong. Should be WARN_ON_ONCE(parent->unsync); > > > > > > > > so how was this tested? > > > > > > > I ran access test in kvm-unit-test for previous version, which hasn't > > this code(also in my local repo "enable_ept" was explicitly set to > > 0 in order to test the shadow mode). But I did not test this one. I'm > > truely sorry for the negligence - even trying to compile should make > > this happen! > > > > Should we submit another version? Any suggestions on the test cases? > > Yes, please send v3. > > The commit message can be: > > In shadow page table, only leaf SPs may be marked as unsync; instead, for > non-leaf SPs, we store the number of unsynced children in unsync_children. > Therefore, in kvm_mmu_sync_root(), sp->unsync > shall always be zero for the root SP and there is no need to check > it. Remove the check, and add a warning inside mmu_sync_children() to > assert that the flags are used properly. > > While at it, move the warning from mmu_need_write_protect() to > kvm_unsync_page(). Thanks Paolo. Will send out v3. BTW, I just realized that mmu_sync_children() was not triggered by kvm-unit-test(the access.flat case), so I ran another test by running a regular VM using shadow, in which I witnessed the synchronization. B.R. Yu > > Paolo >
