linux-kernel - [PATCH RFC 0/2] KVM: TDX: MWAIT in guest

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Message-ID: <20250816144436.83718-1-adrian.hunter@intel.com>
Date: Sat, 16 Aug 2025 17:44:33 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: pbonzini@...hat.com,
	seanjc@...gle.com
Cc: kvm@...r.kernel.org,
	rick.p.edgecombe@...el.com,
	kirill.shutemov@...ux.intel.com,
	kai.huang@...el.com,
	reinette.chatre@...el.com,
	xiaoyao.li@...el.com,
	tony.lindgren@...ux.intel.com,
	binbin.wu@...ux.intel.com,
	isaku.yamahata@...el.com,
	linux-kernel@...r.kernel.org,
	yan.y.zhao@...el.com,
	chao.gao@...el.com,
	ira.weiny@...el.com
Subject: [PATCH RFC 0/2] KVM: TDX: MWAIT in guest

Hi

TDX support for using the MWAIT instruction in a guest has issues.

One option is just to disable it, see patch 1.

Then perhaps provide a distinct way to enable it, documenting the
limitations TDX has compared with VMX in this regard, so that users
will be made aware of the limitations.  See patch 2.

Other options:
1. Do nothing but document the limitations.
2. Patch 1 but not patch 2; look for a better solution


Adrian Hunter (2):
      KVM: TDX: Disable general support for MWAIT in guest
      KVM: TDX: Add flag to support MWAIT instruction only

 Documentation/virt/kvm/x86/intel-tdx.rst | 28 ++++++++++-
 arch/x86/include/asm/kvm_host.h          |  2 +
 arch/x86/include/uapi/asm/kvm.h          |  3 ++
 arch/x86/kvm/vmx/tdx.c                   | 80 +++++++++++++++++++++++++-------
 arch/x86/kvm/x86.c                       |  8 ++--
 5 files changed, 98 insertions(+), 23 deletions(-)


Regards
Adrian