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

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Message-ID: <20231009133655.3aqi4kwx7wtqgqtm@box.shutemov.name>
Date:   Mon, 9 Oct 2023 16:36:55 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     Baoquan He <bhe@...hat.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 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.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov