Re: [RFC PATCH 03/21] i386/kvm: handle Xen HVM cpuid leaves - Philippe Mathieu-Daudé

From: "Philippe Mathieu-Daudé" <philmd@linaro.org>
To: David Woodhouse <dwmw2@infradead.org>, qemu-devel@nongnu.org
Cc: Paolo Bonzini <pbonzini@redhat.com>, Paul Durrant <paul@xen.org>,
	Joao Martins <joao.m.martins@oracle.com>,
	Ankur Arora <ankur.a.arora@oracle.com>
Subject: Re: [RFC PATCH 03/21] i386/kvm: handle Xen HVM cpuid leaves
Date: Mon, 5 Dec 2022 22:58:40 +0100	[thread overview]
Message-ID: <68be4619-50a1-83a9-290d-05618002b47d@linaro.org> (raw)
In-Reply-To: <20221205173137.607044-4-dwmw2@infradead.org>

Hi David,

On 5/12/22 18:31, David Woodhouse wrote:
> From: Joao Martins <joao.m.martins@oracle.com>
> 
> Introduce support for emulating CPUID for Xen HVM guests via
> xen, xen_vapic as changeable params.
> 
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> [dwmw2: Obtain xen_version from machine property]
> Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
> ---
>   target/i386/cpu.c     |  2 ++
>   target/i386/cpu.h     |  3 ++
>   target/i386/kvm/kvm.c | 72 +++++++++++++++++++++++++++++++++++++++++++
>   target/i386/xen.h     |  8 +++++
>   4 files changed, 85 insertions(+)
> 
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index 22b681ca37..45aa9e40a5 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -7069,6 +7069,8 @@ static Property x86_cpu_properties[] = {
>        * own cache information (see x86_cpu_load_def()).
>        */
>       DEFINE_PROP_BOOL("legacy-cache", X86CPU, legacy_cache, true),
> +    DEFINE_PROP_BOOL("xen", X86CPU, xen, false),

Maybe name it 'xen-hvm'?

> +    DEFINE_PROP_BOOL("xen-vapic", X86CPU, xen_vapic, false),

What happens if we use -cpu host,-kvm,+xen,-xen-vapic ?

Is -cpu host,-kvm,-xen,+xen-vapic meaningful? Otherwise we need to error
out (eventually displaying some hint).

>   
>       /*
>        * From "Requirements for Implementing the Microsoft
> diff --git a/target/i386/cpu.h b/target/i386/cpu.h
> index d4bc19577a..5ddd14467e 100644
> --- a/target/i386/cpu.h
> +++ b/target/i386/cpu.h
> @@ -1964,6 +1964,9 @@ struct ArchCPU {
>       int32_t thread_id;
>   
>       int32_t hv_max_vps;
> +
> +    bool xen;
> +    bool xen_vapic;
>   };