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From: Juergen Gross <jgross@suse.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 1/3] xen: check required Xen features
Date: Mon, 10 May 2021 15:21:51 +0200	[thread overview]
Message-ID: <d53d6b83-2730-1ab6-7dba-236e86e247b3@suse.com> (raw)
In-Reply-To: <4282bb6f-1d19-4d00-d468-f5d4c7fb0f90@oracle.com>


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On 10.05.21 14:11, Boris Ostrovsky wrote:
> 
> On 4/22/21 11:10 AM, Juergen Gross wrote:
>>   
>> +/*
>> + * Linux kernel expects at least Xen 4.0.
>> + *
>> + * Assume some features to be available for that reason (depending on guest
>> + * mode, of course).
>> + */
>> +#define chk_feature(f) {						\
>> +		if (!xen_feature(f))					\
>> +			pr_err("Xen: feature %s not available!\n", #f);	\
>> +	}
> 
> 
> With your changes in the subsequent patches, are we still going to function properly without those features? (i.e. maybe we should just panic)

Depends on the use case.

XENFEAT_gnttab_map_avail_bits is relevant for driver domains using
user space backends only. In case it is not available "interesting"
things might happen.

XENFEAT_mmu_pt_update_preserve_ad not being present would result in
a subsequent mmu-update function using that feature returning -ENOSYS,
so this wouldn't be unrecognized.

So panic() might be a good idea in case the features are not available.

> (Also, chk_required_features() perhaps?)

Fine with me.


Juergen

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  reply	other threads:[~2021-05-10 13:22 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-22 15:10 [PATCH 0/3] xen: remove some checks for always present " Juergen Gross
2021-04-22 15:10 ` [PATCH 1/3] xen: check required " Juergen Gross
2021-04-22 15:26   ` Stefano Stabellini
2021-04-22 15:32     ` Juergen Gross
2021-05-10 12:11   ` Boris Ostrovsky
2021-05-10 13:21     ` Juergen Gross [this message]
2021-04-22 15:10 ` [PATCH 2/3] xen: assume XENFEAT_mmu_pt_update_preserve_ad being set for pv guests Juergen Gross
2021-04-22 15:10 ` [PATCH 3/3] xen: assume XENFEAT_gnttab_map_avail_bits " Juergen Gross
2021-04-22 15:16 ` [PATCH 0/3] xen: remove some checks for always present Xen features Jan Beulich
2021-04-22 15:17   ` Juergen Gross
2021-04-22 15:23     ` Jan Beulich
2021-04-22 15:28       ` Juergen Gross
2021-04-22 15:42         ` Jan Beulich
2021-04-22 15:49           ` Juergen Gross
2021-04-22 15:51           ` Andrew Cooper
2021-05-10  7:34 ` Juergen Gross
2021-05-10 11:31   ` Peter Zijlstra

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