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

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Message-ID: <cc060b97dbc56b5a7547d92ec0e624b7686fd55d.camel@intel.com>
Date: Wed, 14 May 2025 22:09:45 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "thomas.lendacky@....com" <thomas.lendacky@....com>, "tglx@...utronix.de"
	<tglx@...utronix.de>, "peterz@...radead.org" <peterz@...radead.org>, "Hansen,
 Dave" <dave.hansen@...el.com>, "mingo@...hat.com" <mingo@...hat.com>,
	"bp@...en8.de" <bp@...en8.de>
CC: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>, "seanjc@...gle.com"
	<seanjc@...gle.com>, "x86@...nel.org" <x86@...nel.org>, "sagis@...gle.com"
	<sagis@...gle.com>, "hpa@...or.com" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>, "Chatre,
 Reinette" <reinette.chatre@...el.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "Williams, Dan J" <dan.j.williams@...el.com>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>, "ashish.kalra@....com"
	<ashish.kalra@....com>, "nik.borisov@...e.com" <nik.borisov@...e.com>
Subject: Re: [PATCH v2 0/5] TDX host: kexec/kdump support

On Wed, 2025-05-14 at 07:37 -0500, Tom Lendacky wrote:
> 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, I appreciate your help!