linux-kernel - Re: [V2 PATCH] x86/tdx: add VIRT_CPUID2 virtualization if REDUCE

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Message-ID: <b138cb84-3a34-40b3-a23d-6ff3708dae6b@intel.com>
Date: Tue, 29 Apr 2025 07:50:13 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Jun Miao <jun.miao@...el.com>, kirill.shutemov@...ux.intel.com,
 dave.hansen@...ux.intel.com, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de
Cc: x86@...nel.org, linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
 fan.du.com@....codeaurora.org, zhiquan1.li@...el.com
Subject: Re: [V2 PATCH] x86/tdx: add VIRT_CPUID2 virtualization if REDUCE_VE
 was not successful

On 4/29/25 07:31, Jun Miao wrote:
> REDUCE_VE can only be enabled if x2APIC_ID has been properly configured
> with unique values for each VCPU.  Check if VMM has provided an activated
> topology configuration first as it is the prerequisite of REDUCE_VE and
> ENUM_TOPOLOGY, so move it to reduce_unnecessary_ve().  The function
> enable_cpu_topology_enumeration() was very little and can be
> integrated into reduce_unnecessary_ve().

Isn't this just working around VMM bugs? Shouldn't we just panic as
quickly as possible so the VMM config gets fixed rather than adding kludges?