linux-kernel - [PATCH v2 17/24] kvm: arm64: Add CPU entry point in nVHE hyp

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Message-Id: <20201116204318.63987-18-dbrazdil@google.com>
Date:   Mon, 16 Nov 2020 20:43:11 +0000
From:   David Brazdil <dbrazdil@...gle.com>
To:     kvmarm@...ts.cs.columbia.edu
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, 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>,
        Quentin Perret <qperret@...gle.com>,
        Andrew Scull <ascull@...gle.com>,
        Andrew Walbran <qwandor@...gle.com>, kernel-team@...roid.com,
        David Brazdil <dbrazdil@...gle.com>
Subject: [PATCH v2 17/24] kvm: arm64: Add CPU entry point in nVHE hyp

When nVHE hyp starts interception host's PSCI CPU_ON SMCs, it will need
to install KVM on the newly booted CPU before returning to the host. Add
an entry point which expects the same kvm_nvhe_init_params struct as the
__kvm_hyp_init HVC in the CPU_ON context argument (x0).

The entry point initializes EL2 state with the same init_el2_state macro
used by the kernel's entry point. It then initializes KVM using the same
helper function used in the __kvm_hyp_init HVC.

When done, the entry point branches to a function provided in the init
params.

Signed-off-by: David Brazdil <dbrazdil@...gle.com>
---
 arch/arm64/include/asm/kvm_asm.h   |  1 +
 arch/arm64/kernel/asm-offsets.c    |  1 +
 arch/arm64/kvm/hyp/nvhe/hyp-init.S | 32 ++++++++++++++++++++++++++++++
 3 files changed, 34 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 01904e88cead..109867fb76f6 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -154,6 +154,7 @@ struct kvm_nvhe_init_params {
 	unsigned long tpidr_el2;
 	unsigned long vector_hyp_va;
 	unsigned long stack_hyp_va;
+	unsigned long entry_hyp_va;
 	phys_addr_t pgd_pa;
 };
 
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 4435ad8be938..9752100bf01f 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -113,6 +113,7 @@ int main(void)
   DEFINE(NVHE_INIT_TPIDR_EL2,	offsetof(struct kvm_nvhe_init_params, tpidr_el2));
   DEFINE(NVHE_INIT_VECTOR_HYP_VA,	offsetof(struct kvm_nvhe_init_params, vector_hyp_va));
   DEFINE(NVHE_INIT_STACK_HYP_VA,	offsetof(struct kvm_nvhe_init_params, stack_hyp_va));
+  DEFINE(NVHE_INIT_ENTRY_HYP_VA,	offsetof(struct kvm_nvhe_init_params, entry_hyp_va));
   DEFINE(NVHE_INIT_PGD_PA,	offsetof(struct kvm_nvhe_init_params, pgd_pa));
 #endif
 #ifdef CONFIG_CPU_PM
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-init.S b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
index d4a71ac34254..6d8202d2bdfb 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-init.S
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-init.S
@@ -9,6 +9,7 @@
 
 #include <asm/alternative.h>
 #include <asm/assembler.h>
+#include <asm/el2_setup.h>
 #include <asm/kvm_arm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmu.h>
@@ -159,6 +160,37 @@ alternative_else_nop_endif
 	ret
 SYM_CODE_END(___kvm_hyp_init)
 
+SYM_CODE_START(__kvm_hyp_cpu_entry)
+	msr	SPsel, #1			// We want to use SP_EL{1,2}
+
+	/* Check that the core was booted in EL2. */
+	mrs	x1, CurrentEL
+	cmp	x1, #CurrentEL_EL2
+	b.eq	2f
+
+	/* The core booted in EL1. KVM cannot be initialized on it. */
+1:	wfe
+	wfi
+	b	1b
+
+	/* Initialize EL2 CPU state to sane values. */
+2:	mov	x29, x0
+	init_el2_state nvhe
+	mov	x0, x29
+
+	/*
+	 * Load hyp VA of C entry function. Must do so before switching on the
+	 * MMU because the struct pointer is PA and not identity-mapped in hyp.
+	 */
+	ldr	x29, [x0, #NVHE_INIT_ENTRY_HYP_VA]
+
+	/* Enable MMU, set vectors and stack. */
+	bl	___kvm_hyp_init
+
+	/* Leave idmap. */
+	br	x29
+SYM_CODE_END(__kvm_hyp_cpu_entry)
+
 SYM_CODE_START(__kvm_handle_stub_hvc)
 	cmp	x0, #HVC_SOFT_RESTART
 	b.ne	1f
-- 
2.29.2.299.gdc1121823c-goog