From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
lantianyu1986@gmail.com
Cc: kvm@vger.kernel.org, rkrcmar@redhat.com, catalin.marinas@arm.com,
will.deacon@arm.com, linux-kernel@vger.kernel.org,
paulus@ozlabs.org, hpa@zytor.com, kys@microsoft.com,
kvmarm@lists.cs.columbia.edu, mpe@ellerman.id.au, x86@kernel.org,
linux@armlinux.org.uk, michael.h.kelley@microsoft.com,
mingo@redhat.com, benh@kernel.crashing.org, jhogan@kernel.org,
linux-mips@vger.kernel.org, Lan Tianyu <Tianyu.Lan@microsoft.com>,
marc.zyngier@arm.com, kvm-ppc@vger.kernel.org, bp@alien8.de,
tglx@linutronix.de, linux-arm-kernel@lists.infradead.org,
christoffer.dall@arm.com, ralf@linux-mips.org,
paul.burton@mips.com, vkuznets@redhat.com,
linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 6/11] KVM/MMU: Flush tlb with range list in sync_page()
Date: Mon, 7 Jan 2019 17:07:58 +0100 [thread overview]
Message-ID: <99e47cc1-43d6-ff05-46b8-6a96ebc34b2a@redhat.com> (raw)
In-Reply-To: <20190104163035.GC11288@linux.intel.com>
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
next prev parent reply other threads:[~2019-01-07 16:08 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-04 8:53 [PATCH 00/11] X86/KVM/Hyper-V: Add HV ept tlb range list flush support in KVM lantianyu1986
2019-01-04 8:53 ` [PATCH 1/11] X86/Hyper-V: Add parameter offset for hyperv_fill_flush_guest_mapping_list() lantianyu1986
2019-01-04 8:53 ` [PATCH 2/11] KVM/VMX: Fill range list in kvm_fill_hv_flush_list_func() lantianyu1986
2019-01-04 8:53 ` [PATCH 3/11] KVM: Add spte's point in the struct kvm_mmu_page lantianyu1986
2019-01-07 16:34 ` Paolo Bonzini
2019-01-04 8:53 ` [PATCH 4/11] KVM/MMU: Introduce tlb flush with range list lantianyu1986
2019-01-07 16:39 ` Paolo Bonzini
2019-01-04 8:53 ` [PATCH 5/11] KVM/MMU: Flush tlb directly in the kvm_mmu_slot_gfn_write_protect() lantianyu1986
2019-01-04 8:54 ` [PATCH 6/11] KVM/MMU: Flush tlb with range list in sync_page() lantianyu1986
[not found] ` <20190104163035.GC11288@linux.intel.com>
2019-01-07 5:13 ` Tianyu Lan
2019-01-07 16:07 ` Paolo Bonzini [this message]
2019-01-04 8:54 ` [PATCH 7/11] KVM: Remove redundant check in the kvm_get_dirty_log_protect() lantianyu1986
[not found] ` <20190104155036.GA11288@linux.intel.com>
2019-01-04 21:27 ` Sean Christopherson
2019-01-07 16:20 ` Paolo Bonzini
2019-01-04 8:54 ` [PATCH 8/11] KVM: Make kvm_arch_mmu_enable_log_dirty_pt_masked() return value lantianyu1986
2019-01-04 8:54 ` [PATCH 9/11] KVM/MMU: Flush tlb in the kvm_mmu_write_protect_pt_masked() lantianyu1986
2019-01-07 16:26 ` Paolo Bonzini
2019-01-10 9:06 ` Tianyu Lan
2019-01-04 8:54 ` [PATCH 10/11] KVM: Add flush parameter for kvm_age_hva() lantianyu1986
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