From: Jan Kiszka <jan.kiszka@web.de>
To: Avi Kivity <avi@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
LKML <linux-kernel@vger.kernel.org>, KVM <kvm@vger.kernel.org>
Subject: Re: [PATCH v6 11/12] KVM: introduce readonly memslot
Date: Sun, 09 Sep 2012 15:52:24 +0200 [thread overview]
Message-ID: <504C9F18.30904@web.de> (raw)
In-Reply-To: <504C9CA9.5010708@redhat.com>
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On 2012-09-09 15:42, Avi Kivity wrote:
> On 09/07/2012 02:14 PM, Jan Kiszka wrote:
>>>
>>> $ grep __KVM_HAVE include/linux/kvm.h | wc -l
>>> 20
>>
>> Yes, mistakes of the past.
>>
>>>
>>> As your suggestion, userspace will always use the CAP even if the CAP
>>> is not really supported. We do not need care the overload on other arches?
>>
>> Generally, userspace can only find out if a CAP is supported by testing
>> during runtime. Sometimes, the CAP may also be used to switch features
>> that are only available on certain archs. But this particular feature
>> should surely become a generic one soon, and the code you could skip in
>> userspace is truly minimal.
>
> You also need them for build time, to see if the ioctl names and
> structures are defined. qemu chose not to do this ifdeffery but we must
> not make that choice for other userspace.
I disagree. We switched QEMU to the pattern the kernel officially
recommends: carry your own headers if you cannot rely on a recent
distribution. The only valid use case for #ifdef KVM_CAP is to allow
disabling of generic code that only some archs can make use of.
I'm not arguing for cleaning up legacy CAPs but for applying this rule
on newly introduced ones.
Jan
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next prev parent reply other threads:[~2012-09-09 13:52 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-21 2:57 [PATCH v6 00/12] KVM: introduce readonly memslot Xiao Guangrong
2012-08-21 2:57 ` [PATCH v6 01/12] KVM: x86: fix possible infinite loop caused by reexecute_instruction Xiao Guangrong
2012-08-22 12:01 ` Avi Kivity
2012-08-22 12:49 ` Xiao Guangrong
2012-08-21 2:58 ` [PATCH v6 02/12] KVM: fix missing check for memslot flags Xiao Guangrong
2012-08-21 2:58 ` [PATCH v6 03/12] KVM: hide KVM_MEMSLOT_INVALID from userspace Xiao Guangrong
2012-08-21 2:59 ` [PATCH v6 04/12] KVM: introduce gfn_to_pfn_memslot_atomic Xiao Guangrong
2012-08-21 2:59 ` [PATCH v6 05/12] KVM: introduce gfn_to_hva_read/kvm_read_hva/kvm_read_hva_atomic Xiao Guangrong
2012-08-21 3:00 ` [PATCH v6 06/12] KVM: reorganize hva_to_pfn Xiao Guangrong
2012-08-21 3:00 ` [PATCH v6 07/12] KVM: use 'writable' as a hint to map writable pfn Xiao Guangrong
2012-08-21 3:01 ` [PATCH v6 08/12] KVM: introduce KVM_PFN_ERR_RO_FAULT Xiao Guangrong
2012-08-21 3:01 ` [PATCH v6 09/12] KVM: introduce KVM_HVA_ERR_BAD Xiao Guangrong
2012-08-21 3:02 ` [PATCH v6 10/12] KVM: introduce KVM_HVA_ERR_RO_BAD Xiao Guangrong
2012-08-21 3:02 ` [PATCH v6 11/12] KVM: introduce readonly memslot Xiao Guangrong
2012-09-07 10:23 ` Jan Kiszka
2012-09-07 10:47 ` Xiao Guangrong
2012-09-07 11:14 ` Jan Kiszka
2012-09-09 13:42 ` Avi Kivity
2012-09-09 13:52 ` Jan Kiszka [this message]
2012-08-21 3:03 ` [PATCH v6 12/12] KVM: indicate readonly access fault Xiao Guangrong
2012-08-22 12:06 ` Avi Kivity
2012-08-22 12:47 ` Xiao Guangrong
2012-09-06 14:09 ` Avi Kivity
2012-09-07 9:56 ` Xiao Guangrong
2012-09-09 13:46 ` Avi Kivity
2012-09-10 22:31 ` Marcelo Tosatti
2012-09-11 9:18 ` Avi Kivity
2012-09-11 14:39 ` Marcelo Tosatti
2012-09-12 15:27 ` Marcelo Tosatti
2012-09-12 15:34 ` Avi Kivity
2012-09-12 15:44 ` Marcelo Tosatti
2012-09-12 15:55 ` Avi Kivity
2012-08-22 12:09 ` [PATCH v6 00/12] KVM: introduce readonly memslot Avi Kivity
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