From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Maxim Levitsky <mlevitsk@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Wanpeng Li <wanpengli@tencent.com>,
Borislav Petkov <bp@alien8.de>, Joerg Roedel <joro@8bytes.org>,
Jim Mattson <jmattson@google.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH 4/7] KVM: nVMX: move inject_page_fault tweak to .complete_mmu_init
Date: Wed, 17 Feb 2021 09:57:55 -0800 [thread overview]
Message-ID: <YC1ZI6DW49u0UP7m@google.com> (raw)
In-Reply-To: <5a8bea9b-deb1-673a-3dc8-f08b679de4c5@redhat.com>
On Wed, Feb 17, 2021, Paolo Bonzini wrote:
> On 17/02/21 18:29, Sean Christopherson wrote:
> > All that being said, I'm pretty we can eliminate setting
> > inject_page_fault dynamically. I think that would yield more
> > maintainable code. Following these flows is a nightmare. The change
> > itself will be scarier, but I'm pretty sure the end result will be a lot
> > cleaner.
>
> I had a similar reaction, though my proposal was different.
>
> The only thing we're changing in complete_mmu_init is the page fault
> callback for init_kvm_softmmu, so couldn't that be the callback directly
> (i.e. something like context->inject_page_fault =
> kvm_x86_ops.inject_softmmu_page_fault)? And then adding is_guest_mode to
> the conditional that is already in vmx_inject_page_fault_nested and
> svm_inject_page_fault_nested.
Heh, that exact code crossed my mind as well.
> That said, I'm also rusty on _why_ this code is needed. Why isn't it enough
> to inject the exception normally, and let nested_vmx_check_exception decide
> whether to inject a vmexit to L1 or an exception into L2?
Hmm, I suspect it was required at one point due to deficiencies elsewhere.
Handling this in the common fault handler logic does seem like the right
approach.
> Also, bonus question which should have been in the 5/7 changelog: are there
> kvm-unit-tests testcases that fail with npt=0, and if not could we write
> one? [Answer: the mode_switch testcase fails, but I haven't checked why].
>
>
> Paolo
>
next prev parent reply other threads:[~2021-02-17 17:59 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-17 14:57 [PATCH 0/7] KVM: random nested fixes Maxim Levitsky
2021-02-17 14:57 ` [PATCH 1/7] KVM: VMX: read idt_vectoring_info a bit earlier Maxim Levitsky
2021-02-17 16:06 ` Paolo Bonzini
2021-02-17 16:18 ` Maxim Levitsky
2021-02-17 16:21 ` Sean Christopherson
2021-02-17 16:29 ` Paolo Bonzini
2021-02-17 14:57 ` [PATCH 2/7] KVM: nSVM: move nested vmrun tracepoint to enter_svm_guest_mode Maxim Levitsky
2021-02-17 14:57 ` [PATCH 3/7] KVM: x86: add .complete_mmu_init arch callback Maxim Levitsky
2021-02-17 14:57 ` [PATCH 4/7] KVM: nVMX: move inject_page_fault tweak to .complete_mmu_init Maxim Levitsky
2021-02-17 17:29 ` Sean Christopherson
2021-02-17 17:37 ` Paolo Bonzini
2021-02-17 17:57 ` Sean Christopherson [this message]
2021-02-17 18:00 ` Paolo Bonzini
2021-02-17 18:49 ` Maxim Levitsky
2021-02-17 18:43 ` Maxim Levitsky
2021-02-18 9:45 ` Paolo Bonzini
2021-02-17 14:57 ` [PATCH 5/7] KVM: nSVM: fix running nested guests when npt=0 Maxim Levitsky
2021-02-17 15:27 ` Maxim Levitsky
2021-02-17 14:57 ` [PATCH 6/7] KVM: nVMX: don't load PDPTRS right after nested state set Maxim Levitsky
2021-02-17 17:52 ` Sean Christopherson
2021-02-17 18:06 ` Paolo Bonzini
2021-02-17 14:57 ` [PATCH 7/7] KVM: nSVM: call nested_svm_load_cr3 on nested state load Maxim Levitsky
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