From: Vivek Goyal <vgoyal@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, x86@kernel.org,
Paolo Bonzini <pbonzini@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
Wanpeng Li <wanpengli@tencent.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Jim Mattson <jmattson@google.com>, Gavin Shan <gshan@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/8] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info
Date: Tue, 26 May 2020 08:50:28 -0400 [thread overview]
Message-ID: <20200526125028.GB108774@redhat.com> (raw)
In-Reply-To: <87sgfq8vau.fsf@vitty.brq.redhat.com>
On Sat, May 23, 2020 at 06:34:17PM +0200, Vitaly Kuznetsov wrote:
> Vivek Goyal <vgoyal@redhat.com> writes:
>
> > On Mon, May 11, 2020 at 06:47:46PM +0200, Vitaly Kuznetsov wrote:
> >> Currently, APF mechanism relies on the #PF abuse where the token is being
> >> passed through CR2. If we switch to using interrupts to deliver page-ready
> >> notifications we need a different way to pass the data. Extent the existing
> >> 'struct kvm_vcpu_pv_apf_data' with token information for page-ready
> >> notifications.
> >>
> >> The newly introduced apf_put_user_ready() temporary puts both reason
> >> and token information, this will be changed to put token only when we
> >> switch to interrupt based notifications.
> >>
> >> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> >> ---
> >> arch/x86/include/uapi/asm/kvm_para.h | 3 ++-
> >> arch/x86/kvm/x86.c | 17 +++++++++++++----
> >> 2 files changed, 15 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
> >> index 2a8e0b6b9805..e3602a1de136 100644
> >> --- a/arch/x86/include/uapi/asm/kvm_para.h
> >> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> >> @@ -113,7 +113,8 @@ struct kvm_mmu_op_release_pt {
> >>
> >> struct kvm_vcpu_pv_apf_data {
> >> __u32 reason;
> >
> > Hi Vitaly,
> >
> > Given we are redoing it, can we convert "reason" into a flag instead
> > and use bit 0 for signalling "page not present" Then rest of the 31
> > bits can be used for other purposes. I potentially want to use one bit to
> > signal error (if it is known at the time of injecting #PF).
>
> Yes, I think we can do that. The existing KVM_PV_REASON_PAGE_READY and
> KVM_PV_REASON_PAGE_NOT_PRESENT are mutually exclusive and can be
> converted to flags (we'll only have KVM_PV_REASON_PAGE_NOT_PRESENT in
> use when this series is merged).
>
> >
> >> - __u8 pad[60];
> >> + __u32 pageready_token;
> >> + __u8 pad[56];
> >
> > Given token is 32 bit, for returning error in "page ready" type messages,
> > I will probably use padding bytes and create pagready_flag and use one
> > of the bits to signal error.
>
> In case we're intended to pass more data in synchronous notifications,
> shall we leave some blank space after 'flags' ('reason' previously) and
> before 'token'?
Given you are planning to move away from using kvm_vcpu_pv_apf_data
for synchronous notifications, I will not be too concerned about it.
Thanks
Vivek
next prev parent reply other threads:[~2020-05-26 12:50 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-11 16:47 [PATCH 0/8] KVM: x86: Interrupt-based mechanism for async_pf 'page present' notifications Vitaly Kuznetsov
2020-05-11 16:47 ` [PATCH 1/8] Revert "KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously" Vitaly Kuznetsov
2020-05-11 16:47 ` [PATCH 2/8] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info Vitaly Kuznetsov
2020-05-12 15:27 ` Vivek Goyal
2020-05-12 15:40 ` Vitaly Kuznetsov
2020-05-12 15:53 ` Vivek Goyal
2020-05-12 17:50 ` Sean Christopherson
2020-05-13 9:09 ` Vitaly Kuznetsov
2020-05-13 12:52 ` Vivek Goyal
2020-05-15 15:59 ` Paolo Bonzini
2020-05-15 18:46 ` Sean Christopherson
2020-05-15 19:18 ` Paolo Bonzini
2020-05-15 20:33 ` Vivek Goyal
2020-05-15 20:53 ` Sean Christopherson
2020-05-15 20:43 ` Sean Christopherson
2020-05-15 22:23 ` Paolo Bonzini
2020-05-15 23:16 ` Sean Christopherson
2020-05-21 14:59 ` Vitaly Kuznetsov
2020-05-22 7:33 ` Paolo Bonzini
2020-05-12 21:15 ` Vivek Goyal
2020-05-21 18:38 ` Vivek Goyal
2020-05-23 16:34 ` Vitaly Kuznetsov
2020-05-26 12:50 ` Vivek Goyal [this message]
2020-05-11 16:47 ` [PATCH 3/8] KVM: introduce kvm_read_guest_offset_cached() Vitaly Kuznetsov
2020-05-11 16:47 ` [PATCH 4/8] KVM: x86: interrupt based APF page-ready event delivery Vitaly Kuznetsov
2020-05-12 14:24 ` Vivek Goyal
2020-05-12 15:50 ` Vitaly Kuznetsov
2020-05-12 18:07 ` Vivek Goyal
2020-05-13 9:03 ` Vitaly Kuznetsov
2020-05-13 13:53 ` Vivek Goyal
2020-05-13 14:03 ` Vivek Goyal
2020-05-13 14:23 ` Vitaly Kuznetsov
2020-05-13 18:46 ` Vivek Goyal
2020-05-14 8:08 ` Vitaly Kuznetsov
2020-05-14 13:31 ` Vivek Goyal
2020-05-11 16:47 ` [PATCH 5/8] KVM: x86: acknowledgment mechanism for async pf page ready notifications Vitaly Kuznetsov
2020-05-11 16:47 ` [PATCH 6/8] KVM: x86: announce KVM_FEATURE_ASYNC_PF_INT Vitaly Kuznetsov
2020-05-11 16:47 ` [PATCH 7/8] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery Vitaly Kuznetsov
2020-05-11 16:47 ` [PATCH 8/8] KVM: x86: drop KVM_PV_REASON_PAGE_READY case from kvm_handle_page_fault() Vitaly Kuznetsov
2020-05-12 15:32 ` [PATCH 0/8] KVM: x86: Interrupt-based mechanism for async_pf 'page present' notifications Vivek Goyal
2020-05-12 16:12 ` Vitaly Kuznetsov
2020-05-13 14:16 ` Vivek Goyal
2020-05-14 18:14 ` Vitaly Kuznetsov
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