linux-kernel - Re: [PATCH v8 05/21] x86/cea: Export API for per-CPU exception stacks for KVM

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Message-Id: <C28589B9-F758-4851-A6FD-41001C99137D@zytor.com>
Date: Thu, 23 Oct 2025 01:55:51 -0700
From: Xin Li <xin@...or.com>
To: Zijlstra Peter <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, pbonzini@...hat.com, seanjc@...gle.com,
        corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
        luto@...nel.org, andrew.cooper3@...rix.com, chao.gao@...el.com,
        hch@...radead.org
Subject: Re: [PATCH v8 05/21] x86/cea: Export API for per-CPU exception stacks for KVM


>> FRED introduced new fields in the host-state area of the VMCS for stack
>> levels 1->3 (HOST_IA32_FRED_RSP[123]), each respectively corresponding to
>> per-CPU exception stacks for #DB, NMI and #DF.  KVM must populate these
>> fields each time a vCPU is loaded onto a CPU.
> 
>> +noinstr unsigned long __this_cpu_ist_top_va(enum exception_stack_ordering stack)
>> +{
>> +    return __this_cpu_ist_bottom_va(stack) + EXCEPTION_STKSZ;
>> +}
>> +EXPORT_SYMBOL(__this_cpu_ist_top_va);
> 
> This has no business being a !GPL export. But please use:
> 
> EXPORT_SYMBOL_FOR_MODULES(__this_cpu_ist_top_val, "kvm");
> 
> (or "kvm-intel", depending on which actual module ends up needing this
> symbol).

Will do “kvm-intel” because that is the only module uses the APIs.