Re: [PATCH v15 17/23] x86/kexec: Flush cache of TDX private memory

[Huang, Kai]

On Mon, 2023-11-27 at 13:06 -0800, Hansen, Dave wrote:
> On 11/27/23 12:52, Huang, Kai wrote:
> > --- a/arch/x86/kernel/machine_kexec_64.c
> > +++ b/arch/x86/kernel/machine_kexec_64.c
> > @@ -377,7 +377,8 @@ void machine_kexec(struct kimage *image)
> >                                        (unsigned long)page_list,
> >                                        image->start,
> >                                        image->preserve_context,
> > -
> > cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT));
> > +                                      cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)
> > > > 
> > +                                      platform_tdx_enabled());
> 
> Well, something more like the attached would be preferable, but you've
> got the right idea logically.

Thanks!

On top of that, I think below code (also attached the diff) should do
advertising the CC_ATTR_HOST_MEM_INCOHERENT for TDX host?

diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index 2e2d559169a8..bec70b967504 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -12,6 +12,8 @@
 
 #include <asm/coco.h>
 #include <asm/processor.h>
+#include <asm/cpufeatures.h>
+#include <asm/tdx.h>
 
 enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
 static u64 cc_mask __ro_after_init;
@@ -23,7 +25,9 @@ static bool noinstr intel_cc_platform_has(enum cc_attr attr)
        case CC_ATTR_HOTPLUG_DISABLED:
        case CC_ATTR_GUEST_MEM_ENCRYPT:
        case CC_ATTR_MEM_ENCRYPT:
-               return true;
+               return cpu_feature_enabled(X86_FEATURE_TDX_GUEST);
+       case CC_ATTR_HOST_MEM_INCOHERENT:
+               return platform_tdx_enabled();
        default:
                return false;
        }
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 73cd2f7b7d87..1ae21348edc1 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1634,6 +1634,13 @@ static int __init tdx_init(void)
        tdx_guest_keyid_start = tdx_keyid_start + 1;
        tdx_nr_guest_keyids = nr_tdx_keyids - 1;
 
+       /*
+        * TDX doesn't guarantee cache coherency among different
+        * KeyIDs.  Advertise the CC_ATTR_HOST_MEM_INCOHERENT
+        * attribute for TDX host.
+        */
+       cc_vendor = CC_VENDOR_INTEL;
+
        return 0;
 }
 early_initcall(tdx_init);


I'll do some test with your code and the above code.
diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index 2e2d559169a8..bec70b967504 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -12,6 +12,8 @@
 
 #include <asm/coco.h>
 #include <asm/processor.h>
+#include <asm/cpufeatures.h>
+#include <asm/tdx.h>
 
 enum cc_vendor cc_vendor __ro_after_init = CC_VENDOR_NONE;
 static u64 cc_mask __ro_after_init;
@@ -23,7 +25,9 @@ static bool noinstr intel_cc_platform_has(enum cc_attr attr)
 	case CC_ATTR_HOTPLUG_DISABLED:
 	case CC_ATTR_GUEST_MEM_ENCRYPT:
 	case CC_ATTR_MEM_ENCRYPT:
-		return true;
+		return cpu_feature_enabled(X86_FEATURE_TDX_GUEST);
+	case CC_ATTR_HOST_MEM_INCOHERENT:
+		return platform_tdx_enabled();
 	default:
 		return false;
 	}
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 73cd2f7b7d87..1ae21348edc1 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1634,6 +1634,13 @@ static int __init tdx_init(void)
 	tdx_guest_keyid_start = tdx_keyid_start + 1;
 	tdx_nr_guest_keyids = nr_tdx_keyids - 1;
 
+	/*
+	 * TDX doesn't guarantee cache coherency among different
+	 * KeyIDs.  Advertise the CC_ATTR_HOST_MEM_INCOHERENT
+	 * attribute for TDX host.
+	 */
+	cc_vendor = CC_VENDOR_INTEL;
+
 	return 0;
 }
 early_initcall(tdx_init);