linux-kernel - Re: [PATCH 00/13] x86/tdx: Add kexec support

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Date:   Mon, 9 Oct 2023 22:13:10 +0800
From:   Baoquan He <bhe@...hat.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        kexec@...ts.infradead.org, linux-coco@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/13] x86/tdx: Add kexec support

On 10/09/23 at 04:36pm, Kirill A. Shutemov wrote:
> On Mon, Oct 09, 2023 at 07:49:35AM +0800, Baoquan He wrote:
> > On 10/05/23 at 04:13pm, Kirill A. Shutemov wrote:
> > > The patchset adds bits and pieces to get kexec (and crashkernel) work on
> > > TDX guest.
> > > 
> > > They bring kexec support to the point when we can start the new kernel,
> > > but it will only be able to use single CPU. It should be enough to cover
> > > the most common case: crashkernel.
> > 
> > Not sure if this question has been raised and answered in the past. Please
> > forgive my bad memory if it has. The one cpu is fine to kdump kernel most
> > of time, while we enable all CPUs by default when kexec rebooting. And kdump
> > kernel with multiple cpu is allowed too. Wondering if there's plan to
> > support the multiple cpu on TDX in the future.
> 
> Sorry, I didn't update this part of cover letter properly, but the last
> patch of the patchset makes possible to kexec with multiple CPUs and the
> 2nd kernel will see them all. It requires support on BIOS side, otherwise
> we fallback to single CPU kexec.

Oops, I didn't read them carefully. You have mentioned that in the last
paragraph of cover letter. That's a great news, thanks.