linux-kernel - [PATCH v9 05/14] x86/msr-index: Add MSRs for Key Locker wrapping key

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Date: Thu, 28 Mar 2024 18:53:37 -0700
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org,
	dm-devel@...hat.com
Cc: ebiggers@...nel.org,
	luto@...nel.org,
	dave.hansen@...ux.intel.com,
	tglx@...utronix.de,
	bp@...en8.de,
	mingo@...nel.org,
	x86@...nel.org,
	herbert@...dor.apana.org.au,
	ardb@...nel.org,
	elliott@....com,
	dan.j.williams@...el.com,
	bernie.keany@...el.com,
	charishma1.gairuboyina@...el.com,
	chang.seok.bae@...el.com
Subject: [PATCH v9 05/14] x86/msr-index: Add MSRs for Key Locker wrapping key

The wrapping key resides in the same power domain as the CPU cache.
Consequently, any sleep state that invalidates the cache, such as S3,
also affects the wrapping key's state.

However, as the wrapping key's state is inaccessible to software, a
specialized mechanism is necessary to save and restore the key during
deep sleep.

A set of new MSRs is provided as an abstract interface for saving,
restoring, and checking the wrapping key's status. The wrapping key
is securely saved in a platform-scoped state using non-volatile media.
Both the backup storage and its path from the CPU are encrypted and
integrity-protected to ensure security.

Define those MSRs for saving and restoring the key during S3/4 sleep
states.

Note that the non-volatility of the backup storage is not architecturally
guaranteed across off-states such as S5 and G3. In such cases, the kernel
may generate a new key during the next boot.

Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Reviewed-by: Dan Williams <dan.j.williams@...el.com>
---
Changes from v8:
* Tweak the changelog.

Changes from v6:
* Tweak the changelog -- put the last for those about other sleep states

Changes from RFC v2:
* Update the changelog. (Dan Williams)
* Rename the MSRs. (Dan Williams)
---
 arch/x86/include/asm/msr-index.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 05956bd8bacf..a451fa1e2cd9 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -1192,4 +1192,10 @@
 						* a #GP
 						*/

+/* MSRs for managing a CPU-internal wrapping key for Key Locker. */
+#define MSR_IA32_IWKEY_COPY_STATUS		0x00000990
+#define MSR_IA32_IWKEY_BACKUP_STATUS		0x00000991
+#define MSR_IA32_BACKUP_IWKEY_TO_PLATFORM	0x00000d91
+#define MSR_IA32_COPY_IWKEY_TO_LOCAL		0x00000d92
+
 #endif /* _ASM_X86_MSR_INDEX_H */
-- 
2.34.1