Re: [PATCH v2 2/5] x86/kexec: do unconditional WBINVD in relocate_kernel()

[Tom Lendacky]

On 3/19/24 06:13, Kirill A. Shutemov 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.
>
> Nope. It breaks TDX guest. WBINVD triggers #VE for TDX guests.

Ditto for SEV-ES/SEV-SNP, a #VC is generated and crashes the guest.

Thanks,
Tom

>