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From: Ben Gardon <bgardon@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>,
	LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
	Cannon Matthews <cannonmatthews@google.com>,
	Peter Xu <peterx@redhat.com>, Peter Shier <pshier@google.com>,
	Peter Feiner <pfeiner@google.com>,
	Junaid Shahid <junaids@google.com>,
	Jim Mattson <jmattson@google.com>,
	Yulei Zhang <yulei.kernel@gmail.com>,
	Wanpeng Li <kernellwp@gmail.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Xiao Guangrong <xiaoguangrong.eric@gmail.com>
Subject: Re: [PATCH 10/22] kvm: mmu: Add TDP MMU PF handler
Date: Tue, 6 Oct 2020 15:35:08 -0700	[thread overview]
Message-ID: <CANgfPd9LmFfZisR3oXKZ7xSeTRi7GyDr+VWf0dE9U4y6_icmTA@mail.gmail.com> (raw)
In-Reply-To: <b123d506-fa33-db3f-1166-4b0ec1d6dc1e@redhat.com>

On Wed, Sep 30, 2020 at 10:38 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 30/09/20 18:37, Sean Christopherson wrote:
> >> +    ret = page_fault_handle_target_level(vcpu, write, map_writable,
> >> +                                         as_id, &iter, pfn, prefault);
> >> +
> >> +    /* If emulating, flush this vcpu's TLB. */
> > Why?  It's obvious _what_ the code is doing, the comment should explain _why_.
> >
> >> +    if (ret == RET_PF_EMULATE)
> >> +            kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> >> +
> >> +    return ret;
> >> +}
>
> In particular it seems to be only needed in this case...
>
> +       /*
> +        * If the page fault was caused by a write but the page is write
> +        * protected, emulation is needed. If the emulation was skipped,
> +        * the vCPU would have the same fault again.
> +        */
> +       if ((make_spte_ret & SET_SPTE_WRITE_PROTECTED_PT) && write)
> +               ret = RET_PF_EMULATE;
> +
>
> ... corresponding to this code in mmu.c
>
>         if (set_spte_ret & SET_SPTE_WRITE_PROTECTED_PT) {
>                 if (write_fault)
>                         ret = RET_PF_EMULATE;
>                 kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
>         }
>
> So it should indeed be better to make the code in
> page_fault_handle_target_level look the same as mmu/mmu.c.

That's an excellent point. I've made an effort to make them more
similar. I think this difference arose from the synchronization
changes I was working back from, but this will be much more elegant in
either case.

>
> Paolo
>

  reply	other threads:[~2020-10-06 22:35 UTC|newest]

Thread overview: 111+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-25 21:22 [PATCH 00/22] Introduce the TDP MMU Ben Gardon
2020-09-25 21:22 ` [PATCH 01/22] kvm: mmu: Separate making SPTEs from set_spte Ben Gardon
2020-09-30  4:55   ` Sean Christopherson
2020-09-30 23:03     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 02/22] kvm: mmu: Introduce tdp_iter Ben Gardon
2020-09-26  0:04   ` Paolo Bonzini
2020-09-30  5:06     ` Sean Christopherson
2020-09-26  0:54   ` Paolo Bonzini
2020-09-30  5:08   ` Sean Christopherson
2020-09-30  5:24   ` Sean Christopherson
2020-09-30  6:24     ` Paolo Bonzini
2020-09-30 23:20   ` Eric van Tassell
2020-09-30 23:34     ` Paolo Bonzini
2020-10-01  0:07       ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 03/22] kvm: mmu: Init / Uninit the TDP MMU Ben Gardon
2020-09-26  0:06   ` Paolo Bonzini
2020-09-30  5:34   ` Sean Christopherson
2020-09-30 18:36     ` Ben Gardon
2020-09-30 16:57   ` Sean Christopherson
2020-09-30 17:39     ` Paolo Bonzini
2020-09-30 18:42       ` Ben Gardon
2020-09-25 21:22 ` [PATCH 04/22] kvm: mmu: Allocate and free TDP MMU roots Ben Gardon
2020-09-30  6:06   ` Sean Christopherson
2020-09-30  6:26     ` Paolo Bonzini
2020-09-30 15:38       ` Sean Christopherson
2020-10-12 22:59     ` Ben Gardon
2020-10-12 23:59       ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 05/22] kvm: mmu: Add functions to handle changed TDP SPTEs Ben Gardon
2020-09-26  0:39   ` Paolo Bonzini
2020-09-28 17:23     ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 06/22] kvm: mmu: Make address space ID a property of memslots Ben Gardon
2020-09-30  6:10   ` Sean Christopherson
2020-09-30 23:11     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 07/22] kvm: mmu: Support zapping SPTEs in the TDP MMU Ben Gardon
2020-09-26  0:14   ` Paolo Bonzini
2020-09-30  6:15   ` Sean Christopherson
2020-09-30  6:28     ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 08/22] kvm: mmu: Separate making non-leaf sptes from link_shadow_page Ben Gardon
2020-09-25 21:22 ` [PATCH 09/22] kvm: mmu: Remove disallowed_hugepage_adjust shadow_walk_iterator arg Ben Gardon
2020-09-30 16:19   ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 10/22] kvm: mmu: Add TDP MMU PF handler Ben Gardon
2020-09-26  0:24   ` Paolo Bonzini
2020-09-30 16:37   ` Sean Christopherson
2020-09-30 16:55     ` Paolo Bonzini
2020-09-30 17:37     ` Paolo Bonzini
2020-10-06 22:35       ` Ben Gardon [this message]
2020-10-06 22:33     ` Ben Gardon
2020-10-07 20:55       ` Sean Christopherson
2020-09-25 21:22 ` [PATCH 11/22] kvm: mmu: Factor out allocating a new tdp_mmu_page Ben Gardon
2020-09-26  0:22   ` Paolo Bonzini
2020-09-30 18:53     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 12/22] kvm: mmu: Allocate struct kvm_mmu_pages for all pages in TDP MMU Ben Gardon
2020-09-25 21:22 ` [PATCH 13/22] kvm: mmu: Support invalidate range MMU notifier for " Ben Gardon
2020-09-30 17:03   ` Sean Christopherson
2020-09-30 23:15     ` Ben Gardon
2020-09-30 23:24       ` Sean Christopherson
2020-09-30 23:27         ` Ben Gardon
2020-09-25 21:22 ` [PATCH 14/22] kvm: mmu: Add access tracking for tdp_mmu Ben Gardon
2020-09-26  0:32   ` Paolo Bonzini
2020-09-30 17:48   ` Sean Christopherson
2020-10-06 23:38     ` Ben Gardon
2020-09-25 21:22 ` [PATCH 15/22] kvm: mmu: Support changed pte notifier in tdp MMU Ben Gardon
2020-09-26  0:33   ` Paolo Bonzini
2020-09-28 15:11   ` Paolo Bonzini
2020-10-07 16:53     ` Ben Gardon
2020-10-07 17:18       ` Paolo Bonzini
2020-10-07 17:30         ` Ben Gardon
2020-10-07 17:54           ` Paolo Bonzini
2020-10-09 10:59   ` Dan Carpenter
2020-10-09 10:59     ` Dan Carpenter
2020-09-25 21:22 ` [PATCH 16/22] kvm: mmu: Add dirty logging handler for changed sptes Ben Gardon
2020-09-26  0:45   ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 17/22] kvm: mmu: Support dirty logging for the TDP MMU Ben Gardon
2020-09-26  1:04   ` Paolo Bonzini
2020-10-08 18:27     ` Ben Gardon
2020-09-29 15:07   ` Paolo Bonzini
2020-09-30 18:04   ` Sean Christopherson
2020-09-30 18:08     ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 18/22] kvm: mmu: Support disabling dirty logging for the tdp MMU Ben Gardon
2020-09-26  1:09   ` Paolo Bonzini
2020-10-07 16:30     ` Ben Gardon
2020-10-07 17:21       ` Paolo Bonzini
2020-10-07 17:28         ` Ben Gardon
2020-10-07 17:53           ` Paolo Bonzini
2020-09-25 21:22 ` [PATCH 19/22] kvm: mmu: Support write protection for nesting in " Ben Gardon
2020-09-30 18:06   ` Sean Christopherson
2020-09-25 21:23 ` [PATCH 20/22] kvm: mmu: NX largepage recovery for TDP MMU Ben Gardon
2020-09-26  1:14   ` Paolo Bonzini
2020-09-30 22:23     ` Ben Gardon
2020-09-29 18:24   ` Paolo Bonzini
2020-09-30 18:15   ` Sean Christopherson
2020-09-30 19:56     ` Paolo Bonzini
2020-09-30 22:33       ` Ben Gardon
2020-09-30 22:27     ` Ben Gardon
2020-10-09 11:03   ` Dan Carpenter
2020-10-09 11:03     ` Dan Carpenter
2020-09-25 21:23 ` [PATCH 21/22] kvm: mmu: Support MMIO in the " Ben Gardon
2020-09-30 18:19   ` Sean Christopherson
2020-10-09 11:43   ` Dan Carpenter
2020-10-09 11:43     ` Dan Carpenter
2020-09-25 21:23 ` [PATCH 22/22] kvm: mmu: Don't clear write flooding count for direct roots Ben Gardon
2020-09-26  1:25   ` Paolo Bonzini
2020-10-05 22:48     ` Ben Gardon
2020-10-05 23:44       ` Sean Christopherson
2020-10-06 16:19         ` Ben Gardon
2020-09-26  1:14 ` [PATCH 00/22] Introduce the TDP MMU Paolo Bonzini
2020-09-28 17:31 ` Paolo Bonzini
2020-09-29 17:40   ` Ben Gardon
2020-09-29 18:10     ` Paolo Bonzini
2020-09-30  6:19 ` Sean Christopherson
2020-09-30  6:30   ` Paolo Bonzini

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