linux-kernel - [PATCH 2/3] KVM: arm64: Generate final CTR_EL0 value when running in Protected mode

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Date:   Mon, 22 Mar 2021 16:48:27 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     catalin.marinas@....com, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com,
        android-kvm@...gle.com, seanjc@...gle.com, mate.toth-pal@....com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-team@...roid.com, kvmarm@...ts.cs.columbia.edu,
        tabba@...gle.com, ardb@...nel.org, mark.rutland@....com,
        dbrazdil@...gle.com
Subject: [PATCH 2/3] KVM: arm64: Generate final CTR_EL0 value when running in Protected mode

In protected mode, late CPUs are not allowed to boot (enforced by
the PSCI relay). We can thus specialise the read_ctr macro to
always return a pre-computed, sanitised value.

Signed-off-by: Marc Zyngier <maz@...nel.org>
---
 arch/arm64/include/asm/assembler.h | 9 +++++++++
 arch/arm64/kernel/image-vars.h     | 1 +
 arch/arm64/kvm/va_layout.c         | 7 +++++++
 3 files changed, 17 insertions(+)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index fb651c1f26e9..1a4cee7eb3c9 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -270,12 +270,21 @@ alternative_endif
  * provide the system wide safe value from arm64_ftr_reg_ctrel0.sys_val
  */
 	.macro	read_ctr, reg
+#ifndef __KVM_NVHE_HYPERVISOR__
 alternative_if_not ARM64_MISMATCHED_CACHE_TYPE
 	mrs	\reg, ctr_el0			// read CTR
 	nop
 alternative_else
 	ldr_l	\reg, arm64_ftr_reg_ctrel0 + ARM64_FTR_SYSVAL
 alternative_endif
+#else
+alternative_cb kvm_compute_final_ctr_el0
+	movz	\reg, #0
+	movk	\reg, #0, lsl #16
+	movk	\reg, #0, lsl #32
+	movk	\reg, #0, lsl #48
+alternative_cb_end
+#endif
 	.endm
 
 
diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h
index d5dc2b792651..fdd60cd1d7e8 100644
--- a/arch/arm64/kernel/image-vars.h
+++ b/arch/arm64/kernel/image-vars.h
@@ -65,6 +65,7 @@ __efistub__ctype		= _ctype;
 KVM_NVHE_ALIAS(kvm_patch_vector_branch);
 KVM_NVHE_ALIAS(kvm_update_va_mask);
 KVM_NVHE_ALIAS(kvm_get_kimage_voffset);
+KVM_NVHE_ALIAS(kvm_compute_final_ctr_el0);
 
 /* Global kernel state accessed by nVHE hyp code. */
 KVM_NVHE_ALIAS(kvm_vgic_global_state);
diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
index 978301392d67..acdb7b3cc97d 100644
--- a/arch/arm64/kvm/va_layout.c
+++ b/arch/arm64/kvm/va_layout.c
@@ -288,3 +288,10 @@ void kvm_get_kimage_voffset(struct alt_instr *alt,
 {
 	generate_mov_q(kimage_voffset, origptr, updptr, nr_inst);
 }
+
+void kvm_compute_final_ctr_el0(struct alt_instr *alt,
+			       __le32 *origptr, __le32 *updptr, int nr_inst)
+{
+	generate_mov_q(read_sanitised_ftr_reg(SYS_CTR_EL0),
+		       origptr, updptr, nr_inst);
+}
-- 
2.29.2