linux-kernel - [PATCH v3 4/5] x86/tdx: tdx_mcall_get_report0: Return -EBUSY on TDCALL_OPERAND

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Message-Id: <20250407-tdx-rtmr-v3-4-54f17bc65228@intel.com>
Date: Mon, 07 Apr 2025 13:59:31 -0500
From: Cedric Xing <cedric.xing@...el.com>
To: Dan Williams <dan.j.williams@...el.com>, 
 "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, 
 Dave Hansen <dave.hansen@...ux.intel.com>, 
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
 Borislav Petkov <bp@...en8.de>, x86@...nel.org, 
 "H. Peter Anvin" <hpa@...or.com>
Cc: linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev, 
 Dionna Amalie Glaze <dionnaglaze@...gle.com>, 
 Guorui Yu <guorui.yu@...ux.alibaba.com>, 
 James Bottomley <James.Bottomley@...senPartnership.com>, 
 Dan Middleton <dan.middleton@...ux.intel.com>, 
 Mikko Ylinen <mikko.ylinen@...ux.intel.com>, 
 Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: [PATCH v3 4/5] x86/tdx: tdx_mcall_get_report0: Return -EBUSY on
 TDCALL_OPERAND_BUSY error

Return `-EBUSY` from tdx_mcall_get_report0() when `TDG.MR.REPORT` returns
`TDCALL_OPERAND_BUSY`. This enables the caller to retry obtaining a
TDREPORT later if another VCPU is extending an RTMR concurrently.

Signed-off-by: Cedric Xing <cedric.xing@...el.com>
---
 arch/x86/coco/tdx/tdx.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index b042ca74bcd3..c94e0061fe53 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -114,8 +114,8 @@ static inline u64 tdg_vm_wr(u64 field, u64 value, u64 mask)
  * v1.0 specification for more information on TDG.MR.REPORT TDCALL.
  * It is used in the TDX guest driver module to get the TDREPORT0.
  *
- * Return 0 on success, -EINVAL for invalid operands, or -EIO on
- * other TDCALL failures.
+ * Return 0 on success, -EINVAL for invalid operands, -EBUSY for busy
+ * operation or -EIO on other TDCALL failures.
  */
 int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
 {
@@ -130,6 +130,8 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
 	if (ret) {
 		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
 			return -EINVAL;
+		else if (TDCALL_RETURN_CODE(ret) == TDCALL_OPERAND_BUSY)
+			return -EBUSY;
 		return -EIO;
 	}

-- 
2.43.0