Patch "RISC-V: KVM: Restrict the extensions that can be disabled" has been added to the 5.17-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    RISC-V: KVM: Restrict the extensions that can be disabled

to the 5.17-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     risc-v-kvm-restrict-the-extensions-that-can-be-disab.patch
and it can be found in the queue-5.17 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 8369a6b7b957f015ec9b320b6a3f6c915c8b217b
Author: Atish Patra <atishp@xxxxxxxxxxxx>
Date:   Tue Apr 19 18:32:58 2022 -0700

    RISC-V: KVM: Restrict the extensions that can be disabled
    
    [ Upstream commit 38d9a4ac65f204f264b33b966f0af4366f5518a8 ]
    
    Currently, the config isa register allows us to disable all allowed
    single letter ISA extensions. It shouldn't be the case as vmm shouldn't
    be able to disable base extensions (imac).
    
    These extensions should always be enabled as long as they are enabled
    in the host ISA.
    
    Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx>
    Signed-off-by: Anup Patel <anup@xxxxxxxxxxxxxx>
    Fixes: 92ad82002c39 ("RISC-V: KVM: Implement
    KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
index 2e25a7b83a1b..aad430668bb4 100644
--- a/arch/riscv/kvm/vcpu.c
+++ b/arch/riscv/kvm/vcpu.c
@@ -38,12 +38,16 @@ const struct kvm_stats_header kvm_vcpu_stats_header = {
 		       sizeof(kvm_vcpu_stats_desc),
 };
 
-#define KVM_RISCV_ISA_ALLOWED	(riscv_isa_extension_mask(a) | \
-				 riscv_isa_extension_mask(c) | \
-				 riscv_isa_extension_mask(d) | \
-				 riscv_isa_extension_mask(f) | \
-				 riscv_isa_extension_mask(i) | \
-				 riscv_isa_extension_mask(m))
+#define KVM_RISCV_ISA_DISABLE_ALLOWED	(riscv_isa_extension_mask(d) | \
+					riscv_isa_extension_mask(f))
+
+#define KVM_RISCV_ISA_DISABLE_NOT_ALLOWED	(riscv_isa_extension_mask(a) | \
+						riscv_isa_extension_mask(c) | \
+						riscv_isa_extension_mask(i) | \
+						riscv_isa_extension_mask(m))
+
+#define KVM_RISCV_ISA_ALLOWED (KVM_RISCV_ISA_DISABLE_ALLOWED | \
+			       KVM_RISCV_ISA_DISABLE_NOT_ALLOWED)
 
 static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
 {
@@ -217,7 +221,8 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
 	switch (reg_num) {
 	case KVM_REG_RISCV_CONFIG_REG(isa):
 		if (!vcpu->arch.ran_atleast_once) {
-			vcpu->arch.isa = reg_val;
+			/* Ignore the disable request for these extensions */
+			vcpu->arch.isa = reg_val | KVM_RISCV_ISA_DISABLE_NOT_ALLOWED;
 			vcpu->arch.isa &= riscv_isa_extension_base(NULL);
 			vcpu->arch.isa &= KVM_RISCV_ISA_ALLOWED;
 			kvm_riscv_vcpu_fp_reset(vcpu);