FAILED: patch "[PATCH] KVM: arm64: ARM_SMCCC_ARCH_WORKAROUND_1 doesn't return" failed to apply to 5.9-stable tree

The patch below does not apply to the 5.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1de111b51b829bcf01d2e57971f8fd07a665fa3f Mon Sep 17 00:00:00 2001
From: Stephen Boyd <[email protected]>
Date: Fri, 23 Oct 2020 08:47:50 -0700
Subject: [PATCH] KVM: arm64: ARM_SMCCC_ARCH_WORKAROUND_1 doesn't return
SMCCC_RET_NOT_REQUIRED

According to the SMCCC spec[1](7.5.2 Discovery) the ARM_SMCCC_ARCH_WORKAROUND_1 function id only returns 0, 1, and SMCCC_RET_NOT_SUPPORTED.

0 is "workaround required and safe to call this function"
1 is "workaround not required but safe to call this function" SMCCC_RET_NOT_SUPPORTED is "might be vulnerable or might not be, who knows, I give up!"

SMCCC_RET_NOT_SUPPORTED might as well mean "workaround required, except calling this function may not work because it isn't implemented in some cases". Wonderful. We map this SMC call to

0 is SPECTRE_MITIGATED
1 is SPECTRE_UNAFFECTED
SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE

For KVM hypercalls (hvc), we've implemented this function id to return SMCCC_RET_NOT_SUPPORTED, 0, and SMCCC_RET_NOT_REQUIRED. One of those isn't supposed to be there. Per the code we call arm64_get_spectre_v2_state() to figure out what to return for this feature discovery call.

0 is SPECTRE_MITIGATED
SMCCC_RET_NOT_REQUIRED is SPECTRE_UNAFFECTED
SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE

Let's clean this up so that KVM tells the guest this mapping:

0 is SPECTRE_MITIGATED
1 is SPECTRE_UNAFFECTED
SMCCC_RET_NOT_SUPPORTED is SPECTRE_VULNERABLE

Note: SMCCC_RET_NOT_AFFECTED is 1 but isn't part of the SMCCC spec

index 25f3c80b5ffe..c18eb7d41274 100644
@@ -135,8 +135,6 @@ static enum mitigation_state spectre_v2_get_cpu_hw_mitigation_state(void)
 	return SPECTRE_VULNERABLE;
 }
 
-#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED	(1)
-
 static enum mitigation_state spectre_v2_get_cpu_fw_mitigation_state(void)
 {
 	int ret;

index 9824025ccc5c..25ea4ecb6449 100644
@@ -31,7 +31,7 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 				val = SMCCC_RET_SUCCESS;
 				break;
 			case SPECTRE_UNAFFECTED:
-				val = SMCCC_RET_NOT_REQUIRED;
+				val = SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED;
 				break;
 			}
 			break;

index 885c9ffc835c..f860645f6512 100644
@@ -87,6 +87,8 @@
 			   ARM_SMCCC_SMC_32,				\
 			   0, 0x7fff)
 
+#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED	1
+
 /* Paravirtualised time calls (defined by ARM DEN0057A) */
 #define ARM_SMCCC_HV_PV_TIME_FEATURES				\
 	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\