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From: Dave Hansen <dave.hansen@intel.com>
To: Vishal Annapurve <vannapurve@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org, bp@alien8.de,
	tglx@linutronix.de, peterz@infradead.org, mingo@redhat.com,
	hpa@zytor.com, thomas.lendacky@amd.com, x86@kernel.org,
	kas@kernel.org, rick.p.edgecombe@intel.com, dwmw@amazon.co.uk,
	kai.huang@intel.com, seanjc@google.com,
	reinette.chatre@intel.com, isaku.yamahata@intel.com,
	dan.j.williams@intel.com, ashish.kalra@amd.com,
	nik.borisov@suse.com, chao.gao@intel.com, sagis@google.com,
	farrah.chen@intel.com, Binbin Wu <binbin.wu@linux.intel.com>
Subject: Re: [PATCH 4/7] x86/kexec: Disable kexec/kdump on platforms with TDX partial write erratum
Date: Wed, 1 Oct 2025 11:00:16 -0700	[thread overview]
Message-ID: <2cbf11a4-fe92-483c-8ab7-182284720700@intel.com> (raw)
In-Reply-To: <CAGtprH_nTBdX-VtMQJM4-y8KcB_F4CnafqpDX7ktASwhO0sxAg@mail.gmail.com>

On 10/1/25 10:17, Vishal Annapurve wrote:
> And also mentions:
> "Also note only the normal kexec needs to worry about this problem, but
> not the crash kexec: 1) The kdump kernel only uses the special memory
> reserved by the first kernel, and the reserved memory can never be used
> by TDX in the first kernel; 2) The /proc/vmcore, which reflects the
> first (crashed) kernel's memory, is only for read.  The read will never
> "poison" TDX memory thus cause unexpected machine check (only partial
> write does)."
> 
> What was the scenario that led to disabling kdump support altogether
> given the above description?

I think it was purely out of convenience so that the disabling could be
three lines of code.

I don't know off the top of my head if there's a simple enough way to
disable kexec but not kdump. When I applied the thing, I was probably
just considering kexec/kdump a monolithic thing and not thinking that
folks would want one but not the other.

Kai, did you have any other motivations?

  reply	other threads:[~2025-10-01 18:00 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-09-01 16:09 [PATCH v8 0/7] TDX host: kexec/kdump support Paolo Bonzini
2025-09-01 16:09 ` [PATCH 1/7] x86/kexec: Consolidate relocate_kernel() function parameters Paolo Bonzini
2025-09-01 16:09 ` [PATCH 2/7] x86/sme: Use percpu boolean to control WBINVD during kexec Paolo Bonzini
2025-09-01 16:09 ` [PATCH 3/7] x86/virt/tdx: Mark memory cache state incoherent when making SEAMCALL Paolo Bonzini
2025-09-01 16:09 ` [PATCH 4/7] x86/kexec: Disable kexec/kdump on platforms with TDX partial write erratum Paolo Bonzini
2025-09-30  1:38   ` Vishal Annapurve
2025-09-30 21:32     ` Dave Hansen
2025-10-01  2:05       ` Vishal Annapurve
2025-10-01 14:32         ` Dave Hansen
2025-10-01 17:17           ` Vishal Annapurve
2025-10-01 18:00             ` Dave Hansen [this message]
2025-10-01 21:19               ` Huang, Kai
2025-10-02  6:59             ` Reshetova, Elena
2025-10-02  7:46               ` Juergen Gross
2025-10-02  8:10                 ` Reshetova, Elena
2025-10-02 15:06                 ` Dave Hansen
2025-10-02 16:09                   ` Vishal Annapurve
2025-10-18 15:54                     ` Vishal Annapurve
2025-10-21 17:08                       ` Dave Hansen
2025-10-22  2:50                         ` Vishal Annapurve
2025-10-22 21:05                           ` Huang, Kai
2025-10-23 16:54                             ` Vishal Annapurve
2025-10-07 13:31                   ` Jürgen Groß
2025-10-08 15:40                     ` Dave Hansen
2025-10-08 18:13                       ` Jürgen Groß
2025-10-26 23:33   ` Vishal Annapurve
2025-10-27  0:50     ` Huang, Kai
2025-10-27 16:23       ` Edgecombe, Rick P
2025-10-27 21:28         ` Huang, Kai
2025-10-28  0:07           ` Vishal Annapurve
2025-10-28  9:31             ` Huang, Kai
2025-11-03 16:44               ` Vishal Annapurve
2025-09-01 16:09 ` [PATCH 5/7] x86/virt/tdx: Remove the !KEXEC_CORE dependency Paolo Bonzini
2025-09-01 16:09 ` [PATCH 6/7] x86/virt/tdx: Update the kexec section in the TDX documentation Paolo Bonzini
2025-09-01 16:09 ` [PATCH 7/7] KVM: TDX: Explicitly do WBINVD when no more TDX SEAMCALLs Paolo Bonzini
2025-10-03 13:09 ` [PATCH v8 0/7] TDX host: kexec/kdump support Paolo Bonzini
2025-10-03 13:54   ` David Woodhouse
2025-10-03 14:05   ` Dave Hansen

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