From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: Vitaly Kuznetsov <vkuznets@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 00/43] KVM: x86: vCPU RESET/INIT fixes and consolidation
Date: Thu, 10 Jun 2021 18:54:40 +0200 [thread overview]
Message-ID: <6ac56ad5-7475-c99f-0ca4-171bc3da45b5@redhat.com> (raw)
In-Reply-To: <20210424004645.3950558-1-seanjc@google.com>
On 24/04/21 02:46, Sean Christopherson wrote:
> For the record, I went into this thinking it was going to be a simple code
> shuffle between {svm,vmx}_vcpu_reset() and kvm_vcpu_reset(). The actual
> goal is to consolidate the RESET/INIT code, both to deduplicate code and
> to try to avoid divergent behavior/bugs, e.g. SVM only recently started
> updating vcpu->arch.cr4 on INIT.
>
> The TL;DR of why it takes 40+ patches to get there is that the RESET/INIT
> flows have multiple latent bugs and hidden dependencies, but "work"
> because they're rarely touched, are mostly fixed flows in both KVM and the
> guest, and because guests don't sanity check state after INIT.
>
> While several of the patches have Fixes tags, I am absolutely terrified of
> backporting most of them due to the likelihood of breaking a different
> version of KVM. And, for the most part the bugs are benign in the sense
> no guest has actually encountered any of these bugs. For that reason, I
> intentionally omitted stable@ entirely. The only patches I would consider
> even remotely safe for backporting are the first two patches in the series.
>
>
> Sean Christopherson (43):
> KVM: nVMX: Set LDTR to its architecturally defined value on nested
> VM-Exit
> KVM: VMX: Set EDX at INIT with CPUID.0x1, Family-Model-Stepping
> KVM: SVM: Require exact CPUID.0x1 match when stuffing EDX at INIT
> KVM: SVM: Fall back to KVM's hardcoded value for EDX at RESET/INIT
> KVM: x86: Split out CR0/CR4 MMU role change detectors to separate
> helpers
> KVM: x86: Properly reset MMU context at vCPU RESET/INIT
> KVM: VMX: Remove explicit MMU reset in enter_rmode()
> KVM: SVM: Drop explicit MMU reset at RESET/INIT
> KVM: SVM: Drop a redundant init_vmcb() from svm_create_vcpu()
> KVM: VMX: Move init_vmcs() invocation to vmx_vcpu_reset()
> KVM: x86: WARN if the APIC map is dirty without an in-kernel local
> APIC
> KVM: x86: Remove defunct BSP "update" in local APIC reset
> KVM: x86: Migrate the PIT only if vcpu0 is migrated, not any BSP
> KVM: x86: Don't force set BSP bit when local APIC is managed by
> userspace
> KVM: x86: Set BSP bit in reset BSP vCPU's APIC base by default
> KVM: VMX: Stuff vcpu->arch.apic_base directly at vCPU RESET
> KVM: x86: Open code necessary bits of kvm_lapic_set_base() at vCPU
> RESET
> KVM: x86: Consolidate APIC base RESET initialization code
> KVM: x86: Move EDX initialization at vCPU RESET to common code
> KVM: SVM: Don't bother writing vmcb->save.rip at vCPU RESET/INIT
> KVM: VMX: Invert handling of CR0.WP for EPT without unrestricted guest
> KVM: VMX: Remove direct write to vcpu->arch.cr0 during vCPU RESET/INIT
> KVM: VMX: Fold ept_update_paging_mode_cr0() back into vmx_set_cr0()
> KVM: nVMX: Do not clear CR3 load/store exiting bits if L1 wants 'em
> KVM: VMX: Pull GUEST_CR3 from the VMCS iff CR3 load exiting is
> disabled
> KVM: VMX: Process CR0.PG side effects after setting CR0 assets
> KVM: VMX: Skip emulation required checks during pmode/rmode
> transitions
> KVM: nVMX: Don't evaluate "emulation required" on VM-Exit
> KVM: SVM: Tweak order of cr0/cr4/efer writes at RESET/INIT
> KVM: SVM: Drop redundant writes to vmcb->save.cr4 at RESET/INIT
> KVM: SVM: Stuff save->dr6 at during VMSA sync, not at RESET/INIT
> KVM: VMX: Skip pointless MSR bitmap update when setting EFER
> KVM: VMX: Refresh list of user return MSRs after setting guest CPUID
> KVM: VMX: Don't _explicitly_ reconfigure user return MSRs on vCPU INIT
> KVM: x86: Move setting of sregs during vCPU RESET/INIT to common x86
> KVM: VMX: Remove obsolete MSR bitmap refresh at vCPU RESET/INIT
> KVM: nVMX: Remove obsolete MSR bitmap refresh at nested transitions
> KVM: VMX: Don't redo x2APIC MSR bitmaps when userspace filter is
> changed
> KVM: VMX: Remove unnecessary initialization of msr_bitmap_mode
> KVM: VMX: Smush x2APIC MSR bitmap adjustments into single function
> KVM: VMX: Remove redundant write to set vCPU as active at RESET/INIT
> KVM: VMX: Drop VMWRITEs to zero fields at vCPU RESET
> KVM: x86: Drop pointless @reset_roots from kvm_init_mmu()
>
> arch/x86/include/asm/kvm_host.h | 5 -
> arch/x86/kvm/i8254.c | 3 +-
> arch/x86/kvm/lapic.c | 26 +--
> arch/x86/kvm/mmu.h | 2 +-
> arch/x86/kvm/mmu/mmu.c | 13 +-
> arch/x86/kvm/svm/nested.c | 2 +-
> arch/x86/kvm/svm/sev.c | 1 +
> arch/x86/kvm/svm/svm.c | 33 +---
> arch/x86/kvm/vmx/nested.c | 26 ++-
> arch/x86/kvm/vmx/vmx.c | 271 +++++++++++++-------------------
> arch/x86/kvm/vmx/vmx.h | 5 +-
> arch/x86/kvm/x86.c | 51 +++++-
> 12 files changed, 189 insertions(+), 249 deletions(-)
>
I'm waiting for a v2 of this; it applies with relatively few conflicts,
but there were some comments so it's better if you take care of updating it.
Paolo
next prev parent reply other threads:[~2021-06-10 16:54 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-24 0:46 [PATCH 00/43] KVM: x86: vCPU RESET/INIT fixes and consolidation Sean Christopherson
2021-04-24 0:46 ` [PATCH 01/43] KVM: nVMX: Set LDTR to its architecturally defined value on nested VM-Exit Sean Christopherson
2021-05-19 5:30 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 02/43] KVM: VMX: Set EDX at INIT with CPUID.0x1, Family-Model-Stepping Sean Christopherson
2021-05-19 5:59 ` Reiji Watanabe
2021-05-19 18:47 ` Sean Christopherson
2021-05-21 7:07 ` Reiji Watanabe
2021-05-21 15:28 ` Sean Christopherson
2021-05-24 4:29 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 03/43] KVM: SVM: Require exact CPUID.0x1 match when stuffing EDX at INIT Sean Christopherson
2021-05-19 5:30 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 04/43] KVM: SVM: Fall back to KVM's hardcoded value for EDX at RESET/INIT Sean Christopherson
2021-05-19 5:41 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 05/43] KVM: x86: Split out CR0/CR4 MMU role change detectors to separate helpers Sean Christopherson
2021-05-19 5:31 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 06/43] KVM: x86: Properly reset MMU context at vCPU RESET/INIT Sean Christopherson
2021-05-17 16:57 ` Reiji Watanabe
2021-05-18 20:23 ` Sean Christopherson
2021-05-18 22:42 ` Reiji Watanabe
2021-05-19 17:16 ` Sean Christopherson
2021-05-24 4:57 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 07/43] KVM: VMX: Remove explicit MMU reset in enter_rmode() Sean Christopherson
2021-04-24 0:46 ` [PATCH 08/43] KVM: SVM: Drop explicit MMU reset at RESET/INIT Sean Christopherson
2021-05-19 5:32 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 09/43] KVM: SVM: Drop a redundant init_vmcb() from svm_create_vcpu() Sean Christopherson
2021-05-19 5:32 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 10/43] KVM: VMX: Move init_vmcs() invocation to vmx_vcpu_reset() Sean Christopherson
2021-05-19 5:33 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 11/43] KVM: x86: WARN if the APIC map is dirty without an in-kernel local APIC Sean Christopherson
2021-04-24 0:46 ` [PATCH 12/43] KVM: x86: Remove defunct BSP "update" in local APIC reset Sean Christopherson
2021-05-26 6:54 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 13/43] KVM: x86: Migrate the PIT only if vcpu0 is migrated, not any BSP Sean Christopherson
2021-04-24 0:46 ` [PATCH 14/43] KVM: x86: Don't force set BSP bit when local APIC is managed by userspace Sean Christopherson
2021-05-26 6:55 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 15/43] KVM: x86: Set BSP bit in reset BSP vCPU's APIC base by default Sean Christopherson
2021-05-26 6:55 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 16/43] KVM: VMX: Stuff vcpu->arch.apic_base directly at vCPU RESET Sean Christopherson
2021-05-26 6:55 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 17/43] KVM: x86: Open code necessary bits of kvm_lapic_set_base() " Sean Christopherson
2021-05-26 7:04 ` Reiji Watanabe
2021-05-26 15:15 ` Sean Christopherson
2021-04-24 0:46 ` [PATCH 18/43] KVM: x86: Consolidate APIC base RESET initialization code Sean Christopherson
2021-05-26 7:04 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 19/43] KVM: x86: Move EDX initialization at vCPU RESET to common code Sean Christopherson
2021-05-19 5:45 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 20/43] KVM: SVM: Don't bother writing vmcb->save.rip at vCPU RESET/INIT Sean Christopherson
2021-05-19 5:34 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 21/43] KVM: VMX: Invert handling of CR0.WP for EPT without unrestricted guest Sean Christopherson
2021-04-24 0:46 ` [PATCH 22/43] KVM: VMX: Remove direct write to vcpu->arch.cr0 during vCPU RESET/INIT Sean Christopherson
2021-05-19 5:34 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 23/43] KVM: VMX: Fold ept_update_paging_mode_cr0() back into vmx_set_cr0() Sean Christopherson
2021-04-24 0:46 ` [PATCH 24/43] KVM: nVMX: Do not clear CR3 load/store exiting bits if L1 wants 'em Sean Christopherson
2021-04-24 0:46 ` [PATCH 25/43] KVM: VMX: Pull GUEST_CR3 from the VMCS iff CR3 load exiting is disabled Sean Christopherson
2021-04-24 0:46 ` [PATCH 26/43] KVM: VMX: Process CR0.PG side effects after setting CR0 assets Sean Christopherson
2021-04-24 0:46 ` [PATCH 27/43] KVM: VMX: Skip emulation required checks during pmode/rmode transitions Sean Christopherson
2021-04-24 0:46 ` [PATCH 28/43] KVM: nVMX: Don't evaluate "emulation required" on VM-Exit Sean Christopherson
2021-04-24 0:46 ` [PATCH 29/43] KVM: SVM: Tweak order of cr0/cr4/efer writes at RESET/INIT Sean Christopherson
2021-05-19 18:16 ` Reiji Watanabe
2021-05-19 19:58 ` Sean Christopherson
2021-05-23 23:04 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 30/43] KVM: SVM: Drop redundant writes to vmcb->save.cr4 " Sean Christopherson
2021-05-19 5:35 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 31/43] KVM: SVM: Stuff save->dr6 at during VMSA sync, not " Sean Christopherson
2021-04-24 0:46 ` [PATCH 32/43] KVM: VMX: Skip pointless MSR bitmap update when setting EFER Sean Christopherson
2021-04-24 0:46 ` [PATCH 33/43] KVM: VMX: Refresh list of user return MSRs after setting guest CPUID Sean Christopherson
2021-05-19 5:35 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 34/43] KVM: VMX: Don't _explicitly_ reconfigure user return MSRs on vCPU INIT Sean Christopherson
2021-04-24 0:46 ` [PATCH 35/43] KVM: x86: Move setting of sregs during vCPU RESET/INIT to common x86 Sean Christopherson
2021-05-17 23:50 ` Reiji Watanabe
2021-05-18 21:45 ` Sean Christopherson
2021-05-21 5:19 ` Reiji Watanabe
2021-04-24 0:46 ` [PATCH 36/43] KVM: VMX: Remove obsolete MSR bitmap refresh at vCPU RESET/INIT Sean Christopherson
2021-04-24 0:46 ` [PATCH 37/43] KVM: nVMX: Remove obsolete MSR bitmap refresh at nested transitions Sean Christopherson
2021-04-24 0:46 ` [PATCH 38/43] KVM: VMX: Don't redo x2APIC MSR bitmaps when userspace filter is changed Sean Christopherson
2021-04-24 0:46 ` [PATCH 39/43] KVM: VMX: Remove unnecessary initialization of msr_bitmap_mode Sean Christopherson
2021-04-24 0:46 ` [PATCH 40/43] KVM: VMX: Smush x2APIC MSR bitmap adjustments into single function Sean Christopherson
2021-04-24 0:46 ` [PATCH 41/43] KVM: VMX: Remove redundant write to set vCPU as active at RESET/INIT Sean Christopherson
2021-04-24 0:46 ` [PATCH 42/43] KVM: VMX: Drop VMWRITEs to zero fields at vCPU RESET Sean Christopherson
2021-05-24 21:15 ` Paolo Bonzini
2021-05-24 22:21 ` Jim Mattson
2021-05-24 22:28 ` Sean Christopherson
2021-05-24 22:48 ` Jim Mattson
2021-05-25 1:02 ` Sean Christopherson
2021-04-24 0:46 ` [PATCH 43/43] KVM: x86: Drop pointless @reset_roots from kvm_init_mmu() Sean Christopherson
2021-05-27 19:11 ` Sean Christopherson
2021-05-27 19:25 ` Sean Christopherson
2021-06-10 16:54 ` Paolo Bonzini [this message]
2021-06-10 19:22 ` [PATCH 00/43] KVM: x86: vCPU RESET/INIT fixes and consolidation Sean Christopherson
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