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From: David Woodhouse <dwmw2@infradead.org>
To: paul@xen.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Paul Durrant <pdurrant@amazon.com>,
	Sean Christopherson <seanjc@google.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH v2 09/12] KVM: selftests / xen: set KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID
Date: Mon, 18 Sep 2023 13:26:26 +0100	[thread overview]
Message-ID: <e4934a021c17dc8bfd8b2bdd8a4543e9ffe09e58.camel@infradead.org> (raw)
In-Reply-To: <c91c5ec9-a917-6d20-1401-c11e27d16f90@xen.org>

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On Mon, 2023-09-18 at 13:18 +0100, Paul Durrant wrote:
> On 18/09/2023 12:59, David Woodhouse wrote:
> > On Mon, 2023-09-18 at 11:21 +0000, Paul Durrant wrote:
> > > From: Paul Durrant <pdurrant@amazon.com>
> > > 
> > > If the capability (KVM_XEN_HVM_CONFIG_EVTCHN_SEND) is present then set
> > > the guest's vCPU id to match the chosen vcpu_info offset.
> > 
> > I think from KVM's point of view, the vcpu_id is still zero. As is the
> > vcpu_idx. What you're setting is the *Xen* vcpu_id.
> 
> Ok. I'll clarify the terminology; and I'll need to set it before the 
> shinfo as noted on another thread.
> 
> > 
> > I like that it's *different* to the vcpu_id; we should definitely be
> > testing that case.
> 
> How so?
> 

Well, imagine you'd not got the kernel's get_vcpu_info_cache() right,
and you accidentally used v->vcpu_id instead of v->arch.xen.vcpu_id. An
easy mistake to make, right?

If you had made that mistake (you didn't; I checked), and if those
numbers had happened to be equal in this test... then this test
wouldn't have shown it.


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  reply	other threads:[~2023-09-18 12:27 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-18 11:21 [PATCH v2 00/12] KVM: xen: update shared_info and vcpu_info handling Paul Durrant
2023-09-18 11:21 ` [PATCH v2 01/12] KVM: pfncache: add a map helper function Paul Durrant
2023-09-18 11:21 ` [PATCH v2 02/12] KVM: pfncache: add a mark-dirty helper Paul Durrant
2023-09-18 11:21 ` [PATCH v2 03/12] KVM: pfncache: add a helper to get the gpa Paul Durrant
2023-09-18 11:21 ` [PATCH v2 04/12] KVM: pfncache: base offset check on khva rather than gpa Paul Durrant
2023-09-18 11:21 ` [PATCH v2 05/12] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA Paul Durrant
2023-09-18 11:34   ` David Woodhouse
2023-09-18 12:11     ` Paul Durrant
2023-09-18 12:59       ` David Woodhouse
2023-09-18 13:00         ` Paul Durrant
2023-09-18 11:21 ` [PATCH v2 06/12] KVM: xen: allow shared_info to be mapped by fixed HVA Paul Durrant
2023-09-18 11:21 ` [PATCH v2 07/12] KVM: xen: prepare for using 'default' vcpu_info Paul Durrant
2023-09-18 11:21 ` [PATCH v2 08/12] KVM: xen: automatically use the vcpu_info embedded in shared_info Paul Durrant
2023-09-18 11:49   ` David Woodhouse
2023-09-18 12:15     ` Paul Durrant
2023-09-18 11:21 ` [PATCH v2 09/12] KVM: selftests / xen: set KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID Paul Durrant
2023-09-18 11:59   ` David Woodhouse
2023-09-18 12:18     ` Paul Durrant
2023-09-18 12:26       ` David Woodhouse [this message]
2023-09-18 11:21 ` [PATCH v2 10/12] KVM: selftests / xen: map shared_info using HVA rather than GFN Paul Durrant
2023-09-18 13:19   ` David Woodhouse
2023-09-18 13:24     ` Paul Durrant
2023-09-18 13:30       ` David Woodhouse
2023-09-18 11:21 ` [PATCH v2 11/12] KVM: selftests / xen: don't explicitly set the vcpu_info address Paul Durrant
2023-09-18 13:21   ` David Woodhouse
2023-09-18 13:26     ` Paul Durrant
2023-09-18 13:36       ` David Woodhouse
2023-09-18 13:41         ` Paul Durrant
2023-09-18 14:05           ` David Woodhouse
2023-09-18 14:14             ` Paul Durrant
2023-09-18 11:21 ` [PATCH v2 12/12] KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability Paul Durrant
2023-09-18 13:22   ` David Woodhouse

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