From: "Radim Krčmář" <rkrcmar@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v2] KVM: x86: clean up conditions for asynchronous page fault handling
Date: Mon, 17 Jun 2019 21:23:18 +0200 [thread overview]
Message-ID: <20190617192318.GA13948@flask> (raw)
In-Reply-To: <1560446532-22494-1-git-send-email-pbonzini@redhat.com>
2019-06-13 19:22+0200, Paolo Bonzini:
> Even when asynchronous page fault is disabled, KVM does not want to pause
> the host if a guest triggers a page fault; instead it will put it into
> an artificial HLT state that allows running other host processes while
> allowing interrupt delivery into the guest.
>
> However, the way this feature is triggered is a bit confusing.
> First, it is not used for page faults while a nested guest is
> running: but this is not an issue since the artificial halt
> is completely invisible to the guest, either L1 or L2. Second,
> it is used even if kvm_halt_in_guest() returns true; in this case,
> the guest probably should not pay the additional latency cost of the
> artificial halt, and thus we should handle the page fault in a
> completely synchronous way.
>
> By introducing a new function kvm_can_deliver_async_pf, this patch
> commonizes the code that chooses whether to deliver an async page fault
> (kvm_arch_async_page_not_present) and the code that chooses whether a
> page fault should be handled synchronously (kvm_can_do_async_pf).
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
prev parent reply other threads:[~2019-06-17 19:23 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-13 17:22 [PATCH v2] KVM: x86: clean up conditions for asynchronous page fault handling Paolo Bonzini
2019-06-17 19:23 ` Radim Krčmář [this message]
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