| Message ID | 20200903162304.19694-1-jiangshanlai@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V3] kvm x86/mmu: use KVM_REQ_MMU_SYNC to sync when needed | expand |
Hi, Paolo Could you pick the patch please? I think it'd be better to be merged before v5.9 is released since it fixes a flaw. Thanks Lai On Thu, Sep 3, 2020 at 11:22 PM Lai Jiangshan <jiangshanlai@gmail.com> wrote: > > From: Lai Jiangshan <laijs@linux.alibaba.com> > > When kvm_mmu_get_page() gets a page with unsynced children, the spt > pagetable is unsynchronized with the guest pagetable. But the > guest might not issue a "flush" operation on it when the pagetable > entry is changed from zero or other cases. The hypervisor has the > responsibility to synchronize the pagetables. > > The linux kernel behaves correctly as above for many years, but a recent > commit 8c8560b83390 ("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for > MMU specific flushes") inadvertently included a line of code to change it > without giving any reason in the changelog. It is clear that the commit's > intention was to change KVM_REQ_TLB_FLUSH -> KVM_REQ_TLB_FLUSH_CURRENT, > so we don't unneedlesly flush other contexts but one of the hunks changed > nearby KVM_REQ_MMU_SYNC instead. > > This patch changes it back. > > Fixes: 8c8560b83390("KVM: x86/mmu: Use KVM_REQ_TLB_FLUSH_CURRENT for MMU specific flushes) > Link: https://lore.kernel.org/lkml/20200320212833.3507-26-sean.j.christopherson@intel.com/ > Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com> > Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> > Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> > --- > Changed from v1: > update patch description > > Changed form v2: > update patch description > > arch/x86/kvm/mmu/mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 4e03841f053d..9a93de921f2b 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -2468,7 +2468,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, > } > > if (sp->unsync_children) > - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); > + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); > > __clear_sp_write_flooding_count(sp); > > -- > 2.19.1.6.gb485710b >
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 4e03841f053d..9a93de921f2b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2468,7 +2468,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, } if (sp->unsync_children) - kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu); + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu); __clear_sp_write_flooding_count(sp);