linux-kernel - Re: [PATCH v2 09/12] KVM: selftests / xen: set KVM_XEN_VCPU_ATTR_TYPE_VCPU

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Date:   Mon, 18 Sep 2023 12:59:09 +0100
From:   David Woodhouse <dwmw2@...radead.org>
To:     Paul Durrant <paul@....org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Paul Durrant <pdurrant@...zon.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v2 09/12] KVM: selftests / xen: set
 KVM_XEN_VCPU_ATTR_TYPE_VCPU_ID

On Mon, 2023-09-18 at 11:21 +0000, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@...zon.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.

I like that it's *different* to the vcpu_id; we should definitely be
testing that case. I don't quite know why the code was using
vcpu_info[1] in the shinfo before when we were explicitly setting the
address from userspace; I suppose it didn't matter.

> Also make some cosmetic fixes to the code for clarity.
> 
> Signed-off-by: Paul Durrant <pdurrant@...zon.com>
> ---
> Cc: Sean Christopherson <seanjc@...gle.com>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: David Woodhouse <dwmw2@...radead.org>
> 
> v2:
>  - New in this version.
> ---
>  .../selftests/kvm/x86_64/xen_shinfo_test.c    | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
> index 05898ad9f4d9..49d0c91ee078 100644
> --- a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
> @@ -38,6 +38,8 @@
>  #define VCPU_INFO_VADDR        (SHINFO_REGION_GVA + 0x40)
>  #define RUNSTATE_VADDR (SHINFO_REGION_GVA + PAGE_SIZE + PAGE_SIZE - 15)
>  
> +#define VCPU_ID                1 /* Must correspond to offset of VCPU_INFO_[V]ADDR */
> 

As well as being a bit clearer in the commit comment as noted above,
let's call this XEN_VCPU_ID ? 

With that cleaned up,

Reviewed-by: David Woodhouse <dwmw@...zon.co.uk>


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