linux-kernel - [RFC PATCH 19/20] x86/virt/seamldr: Verify availability of slots for TD-Preserving updates

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Message-ID: <20250523095322.88774-20-chao.gao@intel.com>
Date: Fri, 23 May 2025 02:52:42 -0700
From: Chao Gao <chao.gao@...el.com>
To: linux-coco@...ts.linux.dev,
	x86@...nel.org,
	kvm@...r.kernel.org
Cc: seanjc@...gle.com,
	pbonzini@...hat.com,
	eddie.dong@...el.com,
	kirill.shutemov@...el.com,
	dave.hansen@...el.com,
	dan.j.williams@...el.com,
	kai.huang@...el.com,
	isaku.yamahata@...el.com,
	elena.reshetova@...el.com,
	rick.p.edgecombe@...el.com,
	Chao Gao <chao.gao@...el.com>,
	Farrah Chen <farrah.chen@...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>,
	"H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 19/20] x86/virt/seamldr: Verify availability of slots for TD-Preserving updates

Before initiating TD-Preserving updates, ensure that the limit on
successive TD-Preserving updates has not been exceeded. This is a cheap
check to prevent update failure.

Refresh SEAMLDR info after each update so that userspace can read the
correct value of remaining updates.

Signed-off-by: Chao Gao <chao.gao@...el.com>
Tested-by: Farrah Chen <farrah.chen@...el.com>
---
 arch/x86/virt/vmx/tdx/seamldr.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 93385db56281..fe8f98701429 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -371,6 +371,9 @@ static int seamldr_install_module(const u8 *data, u32 size)
 	if (!info)
 		return -ENOMEM;
 
+	if (!seamldr_info.num_remaining_updates)
+		return -ENOSPC;
+
 	struct seamldr_params *params __free(free_seamldr_params) =
 						init_seamldr_params(data, size);
 	if (IS_ERR(params))
@@ -382,6 +385,8 @@ static int seamldr_install_module(const u8 *data, u32 size)
 	if (ret)
 		return ret;
 
+	WARN_ON_ONCE(get_seamldr_info());
+
 	return tdx_module_post_update(info);
 }
 
-- 
2.47.1