Re: [PATCH v2 2/5] x86/virt/tdx: Pull kexec cache flush logic into arch/x86

[Kiryl Shutsemau]

On Mon, Mar 23, 2026 at 02:59:05PM -0600, Vishal Verma wrote:
> From: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> 
> KVM tries to take care of some required cache flushing earlier in the
> kexec path in order to be kind to some long standing races that can occur
> later in the operation. Until recently, VMXOFF was handled within KVM.
> Since VMX being enabled is required to make a SEAMCALL, it had the best
> per-cpu scoped operation to plug the flushing into. So it is kicked off
> from there.
> 
> This early kexec cache flushing in KVM happens via a syscore shutdown
> callback. Now that VMX enablement control has moved to arch/x86, which has
> grown its own syscore shutdown callback, it no longer make sense for it to
> live in KVM. It fits better with the TDX enablement managing code.
> 
> In addition, future changes will add a SEAMCALL that happens immediately
> before VMXOFF, which means the cache flush in KVM will be too late to
> flush the cache before the last SEAMCALL. So move it to the newly added TDX
> arch/x86 syscore shutdown handler.
> 
> Since tdx_cpu_flush_cache_for_kexec() is no longer needed by KVM, make it
> static and remove the export. Since it is also not part of an operation
> spread across disparate components, remove the redundant comments and
> verbose naming.
> 
> In the existing KVM based code, CPU offline also funnels through
> tdx_cpu_flush_cache_for_kexec(). So the centralization to the arch/x86
> syscore shutdown callback elides this CPU offline time behavior. However,
> WBINVD is already generally done at CPU offline as matter of course. So
> don't bother adding TDX specific logic for this, and rely on the normal
> WBINVD to handle it.
> 
> Acked-by: Kai Huang <kai.huang@xxxxxxxxx>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx>

Acked-by: Kiryl Shutsemau (Meta) <kas@xxxxxxxxxx>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov