Received-SPF: pass (google.com: domain of linux-kernel+bounces-107447-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Date: Tue, 19 Mar 2024 13:13:51 +0200
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To: Kai Huang <kai.huang@intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, dave.hansen@intel.com, 
	bp@alien8.de, 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
Subject: Re: [PATCH v2 2/5] x86/kexec: do unconditional WBINVD in
 relocate_kernel()
Message-ID: <tvembdwwh4immxytlfzlhpvd42dlfsz7sddb7msk23kdduhu3t@ogpc66hklorv>
References: <cover.1710811610.git.kai.huang@intel.com>
 <e1d37efb8951eb1d38493687b10a21b23353e35a.1710811610.git.kai.huang@intel.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <e1d37efb8951eb1d38493687b10a21b23353e35a.1710811610.git.kai.huang@intel.com>

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.

Nope. It breaks TDX guest. WBINVD triggers #VE for TDX guests.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov