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Re: [XEN PATCH v6 1/3] x86/vmx: guard access to cpu_has_vmx_* in common code
- To: Sergiy Kibrik <Sergiy_Kibrik@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 13 Aug 2024 09:20:24 +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: Tue, 13 Aug 2024 07:20:35 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.08.2024 12:08, 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>
I can accept this is being kind of complete, so
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Howver, ...
> ---
> changes in v6:
> - guard all of cpu_has_vmx_* macros
... this clearly isn't the case. For one ...
> --- a/xen/arch/x86/include/asm/hvm/vmx/vmcs.h
> +++ b/xen/arch/x86/include/asm/hvm/vmx/vmcs.h
> @@ -298,69 +298,99 @@ extern u64 vmx_ept_vpid_cap;
> #define VMX_TSC_MULTIPLIER_MAX 0xffffffffffffffffULL
>
> #define cpu_has_wbinvd_exiting \
> - (vmx_secondary_exec_control & SECONDARY_EXEC_WBINVD_EXITING)
> + (IS_ENABLED(CONFIG_INTEL_VMX) && \
> + vmx_secondary_exec_control & SECONDARY_EXEC_WBINVD_EXITING)
... a few lines up from here there is cpu_has_vmx_virt_spec_ctrl. And
there are quite a few more in vmx.h (don't ask me why things are split
like this). Yet on the grounds that at least this one block of code
now is consistent, I think we can leave further adjustments to possible
later commits.
Jan
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