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Re: [XEN PATCH v5 09/13] x86/vmx: guard access to cpu_has_vmx_* in common code
- To: Sergiy Kibrik <sergiy_kibrik@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 2 Aug 2024 13:10:00 +0200
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Xenia Ragiadakou <xenia.ragiadakou@xxxxxxx>, Paul Durrant <paul@xxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Fri, 02 Aug 2024 11:10:07 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02.08.2024 12:53, Sergiy Kibrik wrote:
> 31.07.24 15:23, Jan Beulich:
>> On 30.07.2024 12:33, Sergiy Kibrik wrote:
>>> There're several places in common code, outside of arch/x86/hvm/vmx,
>>> where cpu_has_vmx_* get accessed without checking whether VMX supported
>>> first.
>>> These macros rely on global variables defined in vmx code, so when VMX
>>> support
>>> is disabled accesses to these variables turn into build failures.
>>>
>>> To overcome these failures, build-time check is done before accessing global
>>> variables, so that DCE would remove these variables.
>>>
>>> Signed-off-by: Sergiy Kibrik<Sergiy_Kibrik@xxxxxxxx>
>>> Acked-by: Paul Durrant<paul@xxxxxxx>
>>> CC: Andrew Cooper<andrew.cooper3@xxxxxxxxxx>
>>> CC: Jan Beulich<jbeulich@xxxxxxxx>
>>> ---
>>> changes in v5:
>>> - change kconfig option name VMX -> INTEL_VMX
>>> - do not change .c files, only modify macros in vmcs.h
>> Better, yet still not going far enough, as indicated earlier:
>
> I must've misunderstood your earlier suggestion. Are we talking about
> modifying all of cpu_has_vmx_* macros -- even though most of them used
> internally to VMX code and don't cause any trouble in common code?
Yes. Where exactly they're used can change any moment (in principle at
least).
Jan
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