[PATCH 1/2] x86/tdx: Handle TDG.MEM.PAGE.ACCEPT success-with-warning returns

["Marc-André Lureau" <marcandre.lureau@redhat.com>]

try_accept_one() treats any non-zero return from __tdcall() as a
failure. However, per the TDX Module Base Spec (Table SEPT Walk Cases),
TDG.MEM.PAGE.ACCEPT returns a non-zero status code with bit 63 clear
when the target page is already in MAPPED state (i.e., already
accepted). This is a "success-with-warning" -- the page is usable and no
action is needed.

Check only bit 63 (TDX_ERROR) to distinguish real errors from
success-with-warning returns, rather than treating all non-zero values
as failures.

Assisted-by: Claude:claude-opus-4-6
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 arch/x86/coco/tdx/tdx-shared.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/coco/tdx/tdx-shared.c b/arch/x86/coco/tdx/tdx-shared.c
index 1655aa56a0a51..24983601a2ded 100644
--- a/arch/x86/coco/tdx/tdx-shared.c
+++ b/arch/x86/coco/tdx/tdx-shared.c
@@ -35,7 +35,7 @@ static unsigned long try_accept_one(phys_addr_t start, unsigned long len,
 	}
 
 	args.rcx = start | page_size;
-	if (__tdcall(TDG_MEM_PAGE_ACCEPT, &args))
+	if (__tdcall(TDG_MEM_PAGE_ACCEPT, &args) & TDX_ERROR)
 		return 0;
 
 	return accept_size;

-- 
2.53.0