linux-kernel - [RFC PATCH 28/28] HACK: Accept prototype RMI versions

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Message-Id: <20230127112932.38045-29-steven.price@arm.com>
Date:   Fri, 27 Jan 2023 11:29:32 +0000
From:   Steven Price <steven.price@....com>
To:     kvm@...r.kernel.org, kvmarm@...ts.linux.dev
Cc:     Steven Price <steven.price@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        James Morse <james.morse@....com>,
        Oliver Upton <oliver.upton@...ux.dev>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Joey Gouly <joey.gouly@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Christoffer Dall <christoffer.dall@....com>,
        Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev
Subject: [RFC PATCH 28/28] HACK: Accept prototype RMI versions

The upstream RMM currently advertises the major version of an internal
prototype (v56.0) rather than the expected version from the RMM
architecture specification (v1.0).

Add a config option to enable support for the prototype RMI v56.0.

Signed-off-by: Steven Price <steven.price@....com>
---
 arch/arm64/include/asm/rmi_smc.h | 7 +++++++
 arch/arm64/kvm/Kconfig           | 8 ++++++++
 arch/arm64/kvm/rme.c             | 8 ++++++++
 3 files changed, 23 insertions(+)

diff --git a/arch/arm64/include/asm/rmi_smc.h b/arch/arm64/include/asm/rmi_smc.h
index 16ff65090f3a..d6bbd7d92b8f 100644
--- a/arch/arm64/include/asm/rmi_smc.h
+++ b/arch/arm64/include/asm/rmi_smc.h
@@ -6,6 +6,13 @@
 #ifndef __ASM_RME_SMC_H
 #define __ASM_RME_SMC_H
 
+#ifdef CONFIG_RME_USE_PROTOTYPE_HACKS
+
+// Allow the prototype RMI version
+#define PROTOTYPE_RMI_ABI_MAJOR_VERSION  56
+
+#endif /* CONFIG_RME_USE_PROTOTYPE_HACKS */
+
 #include <linux/arm-smccc.h>
 
 #define SMC_RxI_CALL(func)				\
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 05da3c8f7e88..13858a5047fd 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -58,6 +58,14 @@ config NVHE_EL2_DEBUG
 
 	  If unsure, say N.
 
+config RME_USE_PROTOTYPE_HACKS
+	bool "Allow RMM prototype version numbers"
+	default y
+	help
+	  For compatibility with the the current RMM code allow versions
+	  numbers from a prototype implementation as well as the expected
+	  version number from the RMM specification.
+
 config PROTECTED_NVHE_STACKTRACE
 	bool "Protected KVM hypervisor stacktraces"
 	depends on NVHE_EL2_DEBUG
diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
index 1eb76cbee267..894060635226 100644
--- a/arch/arm64/kvm/rme.c
+++ b/arch/arm64/kvm/rme.c
@@ -67,6 +67,14 @@ static int rmi_check_version(void)
 	version_major = RMI_ABI_VERSION_GET_MAJOR(res.a0);
 	version_minor = RMI_ABI_VERSION_GET_MINOR(res.a0);
 
+#ifdef PROTOTYPE_RMI_ABI_MAJOR_VERSION
+	// Support the prototype
+	if (version_major == PROTOTYPE_RMI_ABI_MAJOR_VERSION) {
+		kvm_err("Using prototype RMM support (version %d.%d)\n",
+			version_major, version_minor);
+		return 0;
+	}
+#endif
 	if (version_major != RMI_ABI_MAJOR_VERSION) {
 		kvm_err("Unsupported RMI ABI (version %d.%d) we support %d\n",
 			version_major, version_minor,
-- 
2.34.1