From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 01/10] KVM: VMX: Track common EPTP for Hyper-V's paravirt TLB flush
Date: Wed, 21 Oct 2020 13:57:05 +0200 [thread overview]
Message-ID: <878sbz6bce.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20201020215613.8972-2-sean.j.christopherson@intel.com>
Sean Christopherson <sean.j.christopherson@intel.com> writes:
> Explicitly track the EPTP that is common to all vCPUs instead of
> grabbing vCPU0's EPTP when invoking Hyper-V's paravirt TLB flush.
> Tracking the EPTP will allow optimizing the checks when loading a new
> EPTP and will also allow dropping ept_pointer_match, e.g. by marking
> the common EPTP as invalid.
>
> This also technically fixes a bug where KVM could theoretically flush an
> invalid GPA if all vCPUs have an invalid root. In practice, it's likely
> impossible to trigger a remote TLB flush in such a scenario. In any
> case, the superfluous flush is completely benign.
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 19 ++++++++-----------
> arch/x86/kvm/vmx/vmx.h | 1 +
> 2 files changed, 9 insertions(+), 11 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index bcc097bb8321..6d53bcc4a1a9 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -486,6 +486,7 @@ static void check_ept_pointer_match(struct kvm *kvm)
> }
> }
>
> + to_kvm_vmx(kvm)->hv_tlb_eptp = tmp_eptp;
I was going to suggest you reset hv_tlb_eptp to INVALID_PAGE in case
this check fails (couple lines above) but this function is gone later in
the series and the replacement code in hv_remote_flush_tlb_with_range()
does exactly that.
> to_kvm_vmx(kvm)->ept_pointers_match = EPT_POINTERS_MATCH;
> }
>
> @@ -498,21 +499,18 @@ static int kvm_fill_hv_flush_list_func(struct hv_guest_mapping_flush_list *flush
> range->pages);
> }
>
> -static inline int __hv_remote_flush_tlb_with_range(struct kvm *kvm,
> - struct kvm_vcpu *vcpu, struct kvm_tlb_range *range)
> +static inline int hv_remote_flush_eptp(u64 eptp, struct kvm_tlb_range *range)
> {
> - u64 ept_pointer = to_vmx(vcpu)->ept_pointer;
> -
> /*
> * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs address
> * of the base of EPT PML4 table, strip off EPT configuration
> * information.
> */
> if (range)
> - return hyperv_flush_guest_mapping_range(ept_pointer & PAGE_MASK,
> + return hyperv_flush_guest_mapping_range(eptp & PAGE_MASK,
> kvm_fill_hv_flush_list_func, (void *)range);
> else
> - return hyperv_flush_guest_mapping(ept_pointer & PAGE_MASK);
> + return hyperv_flush_guest_mapping(eptp & PAGE_MASK);
> }
>
> static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
> @@ -530,12 +528,11 @@ static int hv_remote_flush_tlb_with_range(struct kvm *kvm,
> kvm_for_each_vcpu(i, vcpu, kvm) {
> /* If ept_pointer is invalid pointer, bypass flush request. */
> if (VALID_PAGE(to_vmx(vcpu)->ept_pointer))
> - ret |= __hv_remote_flush_tlb_with_range(
> - kvm, vcpu, range);
> + ret |= hv_remote_flush_eptp(to_vmx(vcpu)->ept_pointer,
> + range);
> }
> - } else {
> - ret = __hv_remote_flush_tlb_with_range(kvm,
> - kvm_get_vcpu(kvm, 0), range);
> + } else if (VALID_PAGE(to_kvm_vmx(kvm)->hv_tlb_eptp)) {
> + ret = hv_remote_flush_eptp(to_kvm_vmx(kvm)->hv_tlb_eptp, range);
I assume Hyper-V will swallow IVALID_PAGE without complaining much but
it seems pointless to do anything in this case indeed.
> }
>
> spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
> diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
> index 5961cb897125..3d557a065c01 100644
> --- a/arch/x86/kvm/vmx/vmx.h
> +++ b/arch/x86/kvm/vmx/vmx.h
> @@ -301,6 +301,7 @@ struct kvm_vmx {
> bool ept_identity_pagetable_done;
> gpa_t ept_identity_map_addr;
>
> + hpa_t hv_tlb_eptp;
> enum ept_pointers_status ept_pointers_match;
> spinlock_t ept_pointer_lock;
> };
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
--
Vitaly
next prev parent reply other threads:[~2020-10-21 11:57 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-20 21:56 [PATCH v2 00/10] KVM: VMX: Clean up Hyper-V PV TLB flush Sean Christopherson
2020-10-20 21:56 ` [PATCH v2 01/10] KVM: VMX: Track common EPTP for Hyper-V's paravirt " Sean Christopherson
2020-10-21 11:57 ` Vitaly Kuznetsov [this message]
2020-10-20 21:56 ` [PATCH v2 02/10] KVM: VMX: Stash kvm_vmx in a local variable for Hyper-V " Sean Christopherson
2020-10-21 12:00 ` Vitaly Kuznetsov
2020-10-20 21:56 ` [PATCH v2 03/10] KVM: VMX: Fold Hyper-V EPTP checking into it's only caller Sean Christopherson
2020-10-21 12:08 ` Vitaly Kuznetsov
2020-10-20 21:56 ` [PATCH v2 04/10] KVM: VMX: Do Hyper-V TLB flush iff vCPU's EPTP hasn't been flushed Sean Christopherson
2020-10-21 12:23 ` Vitaly Kuznetsov
2020-10-20 21:56 ` [PATCH v2 05/10] KVM: VMX: Invalidate hv_tlb_eptp to denote an EPTP mismatch Sean Christopherson
2020-10-21 12:39 ` Vitaly Kuznetsov
2020-10-21 16:38 ` Sean Christopherson
2020-10-22 9:03 ` Vitaly Kuznetsov
2020-10-20 21:56 ` [PATCH v2 06/10] KVM: VMX: Don't invalidate hv_tlb_eptp if the new EPTP matches Sean Christopherson
2020-10-21 13:47 ` Vitaly Kuznetsov
2020-10-20 21:56 ` [PATCH v2 07/10] KVM: VMX: Explicitly check for hv_remote_flush_tlb when loading pgd Sean Christopherson
[not found] ` <87r1pr4q8z.fsf@vitty.brq.redhat.com>
2020-10-21 17:30 ` Sean Christopherson
2020-10-20 21:56 ` [PATCH v2 08/10] KVM: VMX: Define Hyper-V paravirt TLB flush fields iff Hyper-V is enabled Sean Christopherson
2020-10-21 14:20 ` Vitaly Kuznetsov
2020-10-20 21:56 ` [PATCH v2 09/10] KVM: VMX: Skip additional Hyper-V TLB EPTP flushes if one fails Sean Christopherson
2020-10-21 14:22 ` Vitaly Kuznetsov
2020-10-20 21:56 ` [PATCH v2 10/10] KVM: VMX: Track PGD instead of EPTP for paravirt Hyper-V TLB flush Sean Christopherson
[not found] ` <87imb34p9b.fsf@vitty.brq.redhat.com>
2020-10-21 17:59 ` Sean Christopherson
2020-10-21 9:18 ` [PATCH v2 00/10] KVM: VMX: Clean up Hyper-V PV " Vitaly Kuznetsov
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