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

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Message-Id: <20201126155421.14901-23-dbrazdil@google.com>
Date:   Thu, 26 Nov 2020 15:54:20 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
        Christoph Lameter <cl@...ux.com>,
        Mark Rutland <mark.rutland@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Sudeep Holla <sudeep.holla@....com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-team@...roid.com, David Brazdil <dbrazdil@...gle.com>
Subject: [PATCH v3 22/23] kvm: arm64: Trap host SMCs in protected mode

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@...gle.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