| Message ID | 20190104085405.40356-7-Tianyu.Lan@microsoft.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | X86/KVM/Hyper-V: Add HV ept tlb range list flush support in KVM | expand |
On Sat, Jan 5, 2019 at 12:30 AM Sean Christopherson <sean.j.christopherson@intel.com> wrote: > > On Fri, Jan 04, 2019 at 04:54:00PM +0800, lantianyu1986@gmail.com wrote: > > From: Lan Tianyu <Tianyu.Lan@microsoft.com> > > > > This patch is to flush tlb via flush list function. > > More explanation of why this is beneficial would be nice. Without the > context of the overall series it's not immediately obvious what > kvm_flush_remote_tlbs_with_list() does without a bit of digging. > > > > > Signed-off-by: Lan Tianyu <Tianyu.Lan@microsoft.com> > > --- > > arch/x86/kvm/paging_tmpl.h | 16 ++++++++++++++-- > > 1 file changed, 14 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h > > index 833e8855bbc9..866ccdea762e 100644 > > --- a/arch/x86/kvm/paging_tmpl.h > > +++ b/arch/x86/kvm/paging_tmpl.h > > @@ -973,6 +973,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) > > bool host_writable; > > gpa_t first_pte_gpa; > > int set_spte_ret = 0; > > + LIST_HEAD(flush_list); > > > > /* direct kvm_mmu_page can not be unsync. */ > > BUG_ON(sp->role.direct); > > @@ -980,6 +981,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) > > first_pte_gpa = FNAME(get_level1_sp_gpa)(sp); > > > > for (i = 0; i < PT64_ENT_PER_PAGE; i++) { > > + int tmp_spte_ret = 0; > > unsigned pte_access; > > pt_element_t gpte; > > gpa_t pte_gpa; > > @@ -1029,14 +1031,24 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) > > > > host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE; > > > > - set_spte_ret |= set_spte(vcpu, &sp->spt[i], > > + tmp_spte_ret = set_spte(vcpu, &sp->spt[i], > > pte_access, PT_PAGE_TABLE_LEVEL, > > gfn, spte_to_pfn(sp->spt[i]), > > true, false, host_writable); > > + > > + if (kvm_available_flush_tlb_with_range() > > + && (tmp_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)) { > > + struct kvm_mmu_page *leaf_sp = page_header(sp->spt[i] > > + & PT64_BASE_ADDR_MASK); > > + list_add(&leaf_sp->flush_link, &flush_list); > > + } > > + > > + set_spte_ret |= tmp_spte_ret; > > + > > } > > > > if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH) > > - kvm_flush_remote_tlbs(vcpu->kvm); > > + kvm_flush_remote_tlbs_with_list(vcpu->kvm, &flush_list); > > This is a bit confusing and potentially fragile. It's not obvious that > kvm_flush_remote_tlbs_with_list() is guaranteed to call > kvm_flush_remote_tlbs() when kvm_available_flush_tlb_with_range() is > false, and you're relying on the kvm_flush_remote_tlbs_with_list() call > chain to never optimize away the empty list case. Rechecking > kvm_available_flush_tlb_with_range() isn't expensive. That makes sense. Will update. Thanks. > > > > > return nr_present; > > } > > -- > > 2.14.4 > >
On 04/01/19 17:30, Sean Christopherson wrote: >> + >> + if (kvm_available_flush_tlb_with_range() >> + && (tmp_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)) { >> + struct kvm_mmu_page *leaf_sp = page_header(sp->spt[i] >> + & PT64_BASE_ADDR_MASK); >> + list_add(&leaf_sp->flush_link, &flush_list); >> + } >> + >> + set_spte_ret |= tmp_spte_ret; >> + >> } >> >> if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH) >> - kvm_flush_remote_tlbs(vcpu->kvm); >> + kvm_flush_remote_tlbs_with_list(vcpu->kvm, &flush_list); > This is a bit confusing and potentially fragile. It's not obvious that > kvm_flush_remote_tlbs_with_list() is guaranteed to call > kvm_flush_remote_tlbs() when kvm_available_flush_tlb_with_range() is > false, and you're relying on the kvm_flush_remote_tlbs_with_list() call > chain to never optimize away the empty list case. Rechecking > kvm_available_flush_tlb_with_range() isn't expensive. > Alternatively, do not check it during the loop: always build the flush_list, and always call kvm_flush_remote_tlbs_with_list. The function can then check whether the list is empty, and the OR of tmp_spte_ret on every iteration goes away. Paolo
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h index 833e8855bbc9..866ccdea762e 100644 --- a/arch/x86/kvm/paging_tmpl.h +++ b/arch/x86/kvm/paging_tmpl.h @@ -973,6 +973,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) bool host_writable; gpa_t first_pte_gpa; int set_spte_ret = 0; + LIST_HEAD(flush_list); /* direct kvm_mmu_page can not be unsync. */ BUG_ON(sp->role.direct); @@ -980,6 +981,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) first_pte_gpa = FNAME(get_level1_sp_gpa)(sp); for (i = 0; i < PT64_ENT_PER_PAGE; i++) { + int tmp_spte_ret = 0; unsigned pte_access; pt_element_t gpte; gpa_t pte_gpa; @@ -1029,14 +1031,24 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp) host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE; - set_spte_ret |= set_spte(vcpu, &sp->spt[i], + tmp_spte_ret = set_spte(vcpu, &sp->spt[i], pte_access, PT_PAGE_TABLE_LEVEL, gfn, spte_to_pfn(sp->spt[i]), true, false, host_writable); + + if (kvm_available_flush_tlb_with_range() + && (tmp_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)) { + struct kvm_mmu_page *leaf_sp = page_header(sp->spt[i] + & PT64_BASE_ADDR_MASK); + list_add(&leaf_sp->flush_link, &flush_list); + } + + set_spte_ret |= tmp_spte_ret; + } if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH) - kvm_flush_remote_tlbs(vcpu->kvm); + kvm_flush_remote_tlbs_with_list(vcpu->kvm, &flush_list); return nr_present; }