[PATCH v3 22/23] kvm: arm64: Trap host SMCs in protected mode

David Brazdil
2020-11-26T15:55:32Z

While protected nVHE KVM is installed, start trapping all host SMCs.
By default, these are simply forwarded to EL3, but PSCI SMCs are
validated first.

Create new constant HCR_HOST_NVHE_PROTECTED_FLAGS with the new set of HCR
flags to use while the nVHE vector is installed when the kernel was
booted with the protected flag enabled. Switch back to the default HCR
flags when switching back to the stub vector.

Signed-off-by: David Brazdil <dbrazdil@google.com>
---
arch/arm64/include/asm/kvm_arm.h | 1 +
arch/arm64/kvm/hyp/nvhe/hyp-init.S | 10 ++++++++++
arch/arm64/kvm/hyp/nvhe/switch.c | 5 ++++-
3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 64ce29378467..4e90c2debf70 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -80,6 +80,7 @@
HCR_FMO | HCR_IMO | HCR_PTW )
#define HCR_VIRT_EXCP_MASK (HCR_VSE | HCR_VI | HCR_VF)
#define HCR_HOST_NVHE_FLAGS (HCR_RW | HCR_API | HCR_APK | HCR_ATA)
+#define HCR_HOST_NVHE_PROTECTED_FLAGS (HCR_HOST_NVHE_FLAGS | HCR_TSC)
#define HCR_HOST_VHE_FLAGS (HCR_RW | HCR_TGE | HCR_E2H)

/* TCR_EL2 Registers bits */
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
index fbb195851fb9..7af18fa1983d 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
@@ -88,6 +88,11 @@ SYM_CODE_END(__kvm_hyp_init)
* x0: struct kvm_nvhe_init_params PA
*/
SYM_CODE_START(___kvm_hyp_init)
+alternative_if ARM64_PROTECTED_KVM
+ mov_q x1, HCR_HOST_NVHE_PROTECTED_FLAGS
+ msr hcr_el2, x1
+alternative_else_nop_endif
+
ldr x1, [x0, #NVHE_INIT_TPIDR_EL2]
msr tpidr_el2, x1

@@ -233,6 +238,11 @@ reset:
msr sctlr_el2, x5
isb

+alternative_if ARM64_PROTECTED_KVM
+ mov_q x5, HCR_HOST_NVHE_FLAGS
+ msr hcr_el2, x5
+alternative_else_nop_endif
+
/* Install stub vectors */
adr_l x5, __hyp_stub_vectors
msr vbar_el2, x5
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 3e50ff35aa4f..f3d0e9eca56c 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -97,7 +97,10 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu)
mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;

write_sysreg(mdcr_el2, mdcr_el2);
- write_sysreg(HCR_HOST_NVHE_FLAGS, hcr_el2);
+ if (is_protected_kvm_enabled())
+ write_sysreg(HCR_HOST_NVHE_PROTECTED_FLAGS, hcr_el2);
+ else
+ write_sysreg(HCR_HOST_NVHE_FLAGS, hcr_el2);
write_sysreg(CPTR_EL2_DEFAULT, cptr_el2);
write_sysreg(__kvm_hyp_host_vector, vbar_el2);
}
--
2.29.2.454.gaff20da3a2-goog