Re: [PATCHv13 9/9] x86/tdx: Add unaccepted memory support

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On 6/2/23 08:22, Tom Lendacky wrote:
On 6/1/23 13:25, Kirill A. Shutemov wrote:
Hookup TDX-specific code to accept memory.

Accepting the memory is done with ACCEPT_PAGE module call on every page
in the range. MAP_GPA hypercall is not required as the unaccepted memory
is considered private already.

Extract the part of tdx_enc_status_changed() that does memory acceptance
in a new helper. Move the helper tdx-shared.c. It is going to be used by
both main kernel and decompressor.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
  arch/x86/Kconfig                         |  2 +
  arch/x86/boot/compressed/Makefile        |  2 +-
  arch/x86/boot/compressed/error.c         | 19 +++++++
  arch/x86/boot/compressed/error.h         |  1 +
  arch/x86/boot/compressed/mem.c           | 35 +++++++++++-
  arch/x86/boot/compressed/tdx-shared.c    |  2 +
  arch/x86/coco/tdx/Makefile               |  2 +-
  arch/x86/coco/tdx/tdx-shared.c           | 71 ++++++++++++++++++++++++
  arch/x86/coco/tdx/tdx.c                  | 70 +----------------------
  arch/x86/include/asm/shared/tdx.h        |  2 +
  arch/x86/include/asm/unaccepted_memory.h | 24 ++++++++
  11 files changed, 160 insertions(+), 70 deletions(-)
  create mode 100644 arch/x86/boot/compressed/tdx-shared.c
  create mode 100644 arch/x86/coco/tdx/tdx-shared.c
  create mode 100644 arch/x86/include/asm/unaccepted_memory.h


diff --git a/arch/x86/boot/compressed/mem.c b/arch/x86/boot/compressed/mem.c
index 4ecf26576a77..d2b6948a7801 100644
--- a/arch/x86/boot/compressed/mem.c
+++ b/arch/x86/boot/compressed/mem.c
@@ -2,11 +2,44 @@
  #include "error.h"
  #include "misc.h"
+#include "tdx.h"
+#include <asm/shared/tdx.h>
+
+/*
+ * accept_memory() and process_unaccepted_memory() called from EFI stub which
+ * runs before decompresser and its early_tdx_detect().
+ *
+ * Enumerate TDX directly from the early users.
+ */
+static bool early_is_tdx_guest(void)
+{
+    static bool once;
+    static bool is_tdx;
+
+    if (!IS_ENABLED(CONFIG_INTEL_TDX_GUEST))
+        return false;
+
+    if (!once) {
+        u32 eax, sig[3];
+
+        cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax,
+                &sig[0], &sig[2],  &sig[1]);
+        is_tdx = !memcmp(TDX_IDENT, sig, sizeof(sig));
+        once = true;
+    }
+
+    return is_tdx;
+}
  void arch_accept_memory(phys_addr_t start, phys_addr_t end)
  {
      /* Platform-specific memory-acceptance call goes here */
-    error("Cannot accept memory");
+    if (early_is_tdx_guest()) {
+        if (tdx_accept_memory(start, end))
+            return;
+    }
+
+    error("Cannot accept memory: unknown platform\n");

So this is a change in this version. If tdx_accept_memory() fails, you'll report unknown platform. Wouldn't it be better to have an error message that indicates a failure in the accept path?


Maybe you can keep it similar to the v12 version with just a new error message, something like:

	if (early_is_tdx_guest()) {
		if (!tdx_accept_memory(start, end))
			error("TDX error accepting memory\n");
	} else {
		error("Cannot accept memory: unknown platform\n");
	}

And similar in arch/x86/include/asm/unaccepted_memory.h.

Thanks,
Tom

Thanks,
Tom

  }
  void init_unaccepted_memory(void)




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