Messages in this thread | ![/](/images/icornerl.gif) | | Date | Wed, 10 Apr 2024 17:15:11 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH v3 2/5] x86/kexec: do unconditional WBINVD for bare-metal in relocate_kernel() |
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On Mon, Apr 08, 2024 at 12:44:55AM +1200, 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, to support kexec for TDX host, after stopping all remote cpus > with cache flushed, the kernel needs to flush cache for the last running > cpu. > > Use the existing WBINVD in relocate_kernel() to cover TDX host as well. > > However, instead of sprinkling around vendor-specific checks, just do > unconditional WBINVD to cover both SME and TDX. Kexec is not a fast path > so having one additional WBINVD for platforms w/o SME/TDX is acceptable. > > But only do WBINVD for bare-metal because TDX guests and SEV-ES/SEV-SNP > guests will get unexpected (and yet unnecessary) #VE which the kernel is > unable to handle at this stage. > > Signed-off-by: Kai Huang <kai.huang@intel.com> > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Cc: Dave Young <dyoung@redhat.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
-- Kiryl Shutsemau / Kirill A. Shutemov
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