linux-kernel - Re: [PATCH 7/9] xen/x86: hook up xen

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Date:   Thu, 23 Sep 2021 17:25:30 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Jan Beulich <jbeulich@...e.com>
Cc:     Stefano Stabellini <sstabellini@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [PATCH 7/9] xen/x86: hook up xen_banner() also for PVH

On 23.09.21 17:19, Jan Beulich wrote:
> On 23.09.2021 17:15, Juergen Gross wrote:
>> On 23.09.21 17:10, Jan Beulich wrote:
>>> On 23.09.2021 16:59, Juergen Gross wrote:
>>>> On 07.09.21 12:11, Jan Beulich wrote:
>>>>> This was effectively lost while dropping PVHv1 code. Move the function
>>>>> and arrange for it to be called the same way as done in PV mode. Clearly
>>>>> this then needs re-introducing the XENFEAT_mmu_pt_update_preserve_ad
>>>>> check that was recently removed, as that's a PV-only feature.
>>>>>
>>>>> Signed-off-by: Jan Beulich <jbeulich@...e.com>
>>>>>
>>>>> --- a/arch/x86/xen/enlighten.c
>>>>> +++ b/arch/x86/xen/enlighten.c
>>>>> @@ -261,6 +261,18 @@ int xen_vcpu_setup(int cpu)
>>>>>     	return ((per_cpu(xen_vcpu, cpu) == NULL) ? -ENODEV : 0);
>>>>>     }
>>>>>     
>>>>> +void __init xen_banner(void)
>>>>> +{
>>>>> +	unsigned version = HYPERVISOR_xen_version(XENVER_version, NULL);
>>>>> +	struct xen_extraversion extra;
>>>>
>>>> Please add a blank line here.
>>>
>>> Oops.
>>>
>>>>> +	HYPERVISOR_xen_version(XENVER_extraversion, &extra);
>>>>> +
>>>>> +	pr_info("Booting paravirtualized kernel on %s\n", pv_info.name);
>>>>
>>>> Is this correct? I don't think the kernel needs to be paravirtualized
>>>> with PVH (at least not to the same extend as for PV).
>>>
>>> What else do you suggest the message to say? Simply drop
>>> "paravirtualized"? To some extent it is applicable imo, further
>>> qualified by pv_info.name. And that's how it apparently was with
>>> PVHv1.
>>
>> The string could be selected depending on CONFIG_XEN_PV.
> 
> Hmm, now I'm confused: Doesn't this setting control whether the kernel
> can run in PV mode? If so, that functionality being present should have
> no effect on the functionality of the kernel when running in PVH mode.
> So what you suggest would end up in misleading information imo.

Hmm, yes, I mixed "paravirtualized" with "capable to run
paravirtualized".

So the string should depend on xen_pv_domain().


Juergen

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