linux-kernel - Re: [PATCH v2 0/5] TDX host: kexec/kdump support

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Message-ID: <9a88386d-6610-9ff3-2a71-42961e7168f3@amd.com>
Date: Wed, 14 May 2025 07:37:45 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Kai Huang <kai.huang@...el.com>, dave.hansen@...el.com, bp@...en8.de,
 tglx@...utronix.de, peterz@...radead.org, mingo@...hat.com
Cc: kirill.shutemov@...ux.intel.com, hpa@...or.com, x86@...nel.org,
 linux-kernel@...r.kernel.org, pbonzini@...hat.com, seanjc@...gle.com,
 rick.p.edgecombe@...el.com, isaku.yamahata@...el.com,
 reinette.chatre@...el.com, dan.j.williams@...el.com, ashish.kalra@....com,
 nik.borisov@...e.com, sagis@...gle.com
Subject: Re: [PATCH v2 0/5] TDX host: kexec/kdump support

On 5/10/25 06:20, Kai Huang wrote:
> Hi Dave,
> 
> This series is the latest attempt to support kexec on TDX host following
> your suggestion to use a percpu boolean to control WBINVD during kexec.
> I appreciate if you can help to review.
> 
> The last attempt was to have one patch to make TDX and kexec mutually
> exclusive at runtime while allowing them to be both enabled in Kconfig,
> but it turns out to be overkill.  Dave proposed another option of using
> a percpu boolean to track the need for flushing:
> 
> https://lore.kernel.org/lkml/20250416230259.97989-1-kai.huang@intel.com/
> 
> One advantage of the percpu boolean is for TDX we could do optimization
> to do:
> 
> 	wbinvd();
> 	percpu(boolean) = 0;
> 
> for all CPUs at early stage to avoid having to do WBINVD in
> stop_this_cpu() at kexec time.  I made a RFC patch to show the idea:
> 
> https://github.com/intel/tdx/commit/d9f0123b1d63ba24f472da6971181939ce53d2e3
> 
> I'll also reply this RFC patch to this coverletter in case anyone wants
> to have a discussion.  Nevertheless, my exception is this series can be
> merged first w/o the RFC patch.  We can follow up the optimizations
> later.
> 
> This series is tagged v2, since it's a closer follow on to the RFC
> patchset, which was posted before the single patch:
> 
> https://lore.kernel.org/all/cover.1741778537.git.kai.huang@intel.com/
> 
> This series is based on today's tip/master.

I'm on PTO for the next few days, so I'll try to review/test the SME
related changes when I return.

Thanks,
Tom

>