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From: Vivek Goyal <vgoyal@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
	x86@kernel.org, kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org, Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH RFC 6/6] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery
Date: Tue, 5 May 2020 14:59:35 -0400	[thread overview]
Message-ID: <20200505185935.GC7155@redhat.com> (raw)
In-Reply-To: <ee587bd6-a06f-8a38-9182-94218f7d08bb@redhat.com>

On Wed, Apr 29, 2020 at 12:53:33PM +0200, Paolo Bonzini wrote:
> On 29/04/20 11:36, Vitaly Kuznetsov wrote:
> > +
> > +	if (__this_cpu_read(apf_reason.enabled)) {
> > +		reason = __this_cpu_read(apf_reason.reason);
> > +		if (reason == KVM_PV_REASON_PAGE_READY) {
> > +			token = __this_cpu_read(apf_reason.token);
> > +			/*
> > +			 * Make sure we read 'token' before we reset
> > +			 * 'reason' or it can get lost.
> > +			 */
> > +			mb();
> > +			__this_cpu_write(apf_reason.reason, 0);
> > +			kvm_async_pf_task_wake(token);
> > +		}
> 
> If tokens cannot be zero, could we avoid using reason for the page ready
> interrupt (and ultimately retire "reason" completely)?

If we are planning to report errors using this interface, then retaining
KVM_PV_REASON_PAGE_READY makes sense because we can then introduce another
state say KVM_PV_REASON_PAGE_ERROR.

Thanks
Vivek


  parent reply	other threads:[~2020-05-05 18:59 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-29  9:36 [PATCH RFC 0/6] KVM: x86: Interrupt-based mechanism for async_pf 'page present' notifications Vitaly Kuznetsov
2020-04-29  9:36 ` [PATCH RFC 1/6] Revert "KVM: async_pf: Fix #DF due to inject "Page not Present" and "Page Ready" exceptions simultaneously" Vitaly Kuznetsov
2020-05-05  1:22   ` Gavin Shan
2020-05-05 14:16   ` Vivek Goyal
2020-05-06 15:17     ` Vitaly Kuznetsov
2020-05-11 19:17       ` Vivek Goyal
2020-04-29  9:36 ` [PATCH RFC 2/6] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info Vitaly Kuznetsov
2020-05-04 23:52   ` Gavin Shan
2020-05-05  8:08     ` Vitaly Kuznetsov
2020-04-29  9:36 ` [PATCH RFC 3/6] KVM: x86: interrupt based APF page-ready event delivery Vitaly Kuznetsov
2020-04-29 10:54   ` Paolo Bonzini
2020-04-29 12:40     ` Vitaly Kuznetsov
2020-04-29 13:21       ` Paolo Bonzini
2020-04-29 21:27   ` Peter Xu
2020-04-30  8:31     ` Vitaly Kuznetsov
2020-04-30 13:28       ` Peter Xu
2020-04-30 13:49         ` Vitaly Kuznetsov
2020-05-05 15:22   ` Vivek Goyal
2020-04-29  9:36 ` [PATCH RFC 4/6] KVM: x86: acknowledgment mechanism for async pf page ready notifications Vitaly Kuznetsov
2020-04-29 17:28   ` Andy Lutomirski
2020-04-29 17:40     ` Paolo Bonzini
2020-04-30  0:45       ` Andy Lutomirski
2020-04-30  6:46         ` Paolo Bonzini
2020-04-30  6:49   ` Paolo Bonzini
2020-04-30  8:40     ` Vitaly Kuznetsov
2020-04-30  9:27       ` Paolo Bonzini
2020-04-30 11:33         ` Vitaly Kuznetsov
2020-04-30 11:43           ` Paolo Bonzini
2020-05-05  0:36   ` Gavin Shan
2020-05-05  8:16     ` Vitaly Kuznetsov
2020-05-05  8:51       ` Gavin Shan
2020-05-05  9:54         ` Paolo Bonzini
2020-04-29  9:36 ` [PATCH RFC 5/6] KVM: x86: announce KVM_FEATURE_ASYNC_PF_INT Vitaly Kuznetsov
2020-04-29 10:40   ` Peter Zijlstra
2020-04-29  9:36 ` [PATCH RFC 6/6] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery Vitaly Kuznetsov
2020-04-29 10:53   ` Paolo Bonzini
2020-04-29 12:44     ` Vitaly Kuznetsov
2020-04-29 13:19       ` Paolo Bonzini
2020-04-29 14:34         ` Vitaly Kuznetsov
2020-05-05 18:59     ` Vivek Goyal [this message]
2020-05-05  0:42   ` Gavin Shan

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