diff mbox series

[RFC,v3,47/59] KVM: TDX: Define TDCALL exit reason

Message ID eb5dd2a1d02c7afe320ab3beb6390da43a9bf0bc.1637799475.git.isaku.yamahata@intel.com (mailing list archive)
State New, archived
Headers show
Series KVM: X86: TDX support | expand

Commit Message

Isaku Yamahata Nov. 25, 2021, 12:20 a.m. UTC 
From: Sean Christopherson <sean.j.christopherson@intel.com>

Define the TDCALL exit reason, which is carved out from the VMX exit
reason namespace as the TDCALL exit from TDX guest to TDX-SEAM is really
just a VM-Exit.

Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
 arch/x86/include/uapi/asm/vmx.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Thomas Gleixner Nov. 25, 2021, 8:19 p.m. UTC | #1 
On Wed, Nov 24 2021 at 16:20, isaku yamahata wrote:
> From: Sean Christopherson <sean.j.christopherson@intel.com>
>
> Define the TDCALL exit reason, which is carved out from the VMX exit
> reason namespace as the TDCALL exit from TDX guest to TDX-SEAM is really
> just a VM-Exit.

How is this carved out? What's the value of this word salad?

It's simply a new exit reason. Not more, not less. So what?

> Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>

I'm pretty sure that it does not take two engineers to add a new exit
reason define, but it takes at least two engineers to come up with a
convoluted explanation for it.

Thanks,

        tglx
Sean Christopherson Nov. 29, 2021, 6:36 p.m. UTC | #2 
On Thu, Nov 25, 2021, Thomas Gleixner wrote:
> On Wed, Nov 24 2021 at 16:20, isaku yamahata wrote:
> > From: Sean Christopherson <sean.j.christopherson@intel.com>
> >
> > Define the TDCALL exit reason, which is carved out from the VMX exit
> > reason namespace as the TDCALL exit from TDX guest to TDX-SEAM is really
> > just a VM-Exit.
> 
> How is this carved out? What's the value of this word salad?
> 
> It's simply a new exit reason. Not more, not less. So what?

The changelog is alluding to the fact that KVM should never directly see a TDCALL
VM-Exit.  For TDX, KVM deals only with "returns" from the TDX-Module.  The "carved
out" bit is calling out that the transition from SEAM Non-Root (the TDX guest) to
SEAM Root (the TDX Module) is actually a VT-x/VMX VM-Exit, e.g. if TDX were somehow
implemented without relying on VT-x/VMX, then the TDCALL exit reason wouldn't exist.

> > Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> 
> I'm pretty sure that it does not take two engineers to add a new exit
> reason define, but it takes at least two engineers to come up with a
> convoluted explanation for it.

Nah, just one ;-)
diff mbox series

Patch

diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
index 946d761adbd3..ba5908dfc7c0 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -91,6 +91,7 @@ 
 #define EXIT_REASON_UMWAIT              67
 #define EXIT_REASON_TPAUSE              68
 #define EXIT_REASON_BUS_LOCK            74
+#define EXIT_REASON_TDCALL              77
 
 #define VMX_EXIT_REASONS \
 	{ EXIT_REASON_EXCEPTION_NMI,         "EXCEPTION_NMI" }, \
@@ -153,7 +154,8 @@ 
 	{ EXIT_REASON_XRSTORS,               "XRSTORS" }, \
 	{ EXIT_REASON_UMWAIT,                "UMWAIT" }, \
 	{ EXIT_REASON_TPAUSE,                "TPAUSE" }, \
-	{ EXIT_REASON_BUS_LOCK,              "BUS_LOCK" }
+	{ EXIT_REASON_BUS_LOCK,              "BUS_LOCK" }, \
+	{ EXIT_REASON_TDCALL,                "TDCALL" }
 
 #define VMX_EXIT_REASON_FLAGS \
 	{ VMX_EXIT_REASONS_FAILED_VMENTRY,	"FAILED_VMENTRY" }