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Message-ID: <f4487d93-8207-4d37-b94a-7cb00894a198@intel.com>
Date: Wed, 20 Mar 2024 10:08:09 +1300
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Subject: Re: [PATCH v2 2/5] x86/kexec: do unconditional WBINVD in
 relocate_kernel()
To: Borislav Petkov <bp@alien8.de>
CC: <linux-kernel@vger.kernel.org>, <x86@kernel.org>, <dave.hansen@intel.com>,
	<kirill.shutemov@linux.intel.com>, <tglx@linutronix.de>, <mingo@redhat.com>,
	<hpa@zytor.com>, <luto@kernel.org>, <peterz@infradead.org>,
	<rick.p.edgecombe@intel.com>, <thomas.lendacky@amd.com>,
	<ashish.kalra@amd.com>, <chao.gao@intel.com>, <bhe@redhat.com>,
	<nik.borisov@suse.com>, <pbonzini@redhat.com>, <seanjc@google.com>
References: <cover.1710811610.git.kai.huang@intel.com>
 <e1d37efb8951eb1d38493687b10a21b23353e35a.1710811610.git.kai.huang@intel.com>
 <20240319154111.GEZfmyF7IuQ5THG0qO@fat_crate.local>
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From: "Huang, Kai" <kai.huang@intel.com>
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On 20/03/2024 4:41 am, Borislav Petkov wrote:
> On Tue, Mar 19, 2024 at 01:48:45AM +0000, Kai Huang wrote:
>> Both SME and TDX can leave caches in incoherent state due to memory
>> encryption.  During kexec, the caches must be flushed before jumping to
>> the second kernel to avoid silent memory corruption to the second kernel.
>>
>> During kexec, the WBINVD in stop_this_cpu() flushes caches for all
>> remote cpus when they are being stopped.  For SME, the WBINVD in
>> relocate_kernel() flushes the cache for the last running cpu (which is
>> executing the kexec).
>>
>> Similarly, for TDX after stopping all remote cpus with cache flushed, to
>> support kexec, the kernel needs to flush cache for the last running cpu.
>>
>> Make the WBINVD in the relocate_kernel() unconditional to cover both SME
>> and TDX.
>>
>> Signed-off-by: Kai Huang <kai.huang@intel.com>
>> Suggested-by: Borislav Petkov <bp@alien8.de>
> 
> Well, I suggested what you have in patch 1 but not this.
> 
> You can't just slap tags willy nilly to patches.
> 

Apologize.  Will remove.