[PATCH v3 12/18] KVM: arm64: nVHE: Switch to hyp context for EL2
Andrew Scull
ascull at google.com
Thu Sep 3 09:53:01 EDT 2020
Save and restore the host context when switching to and from hyp. This
gives hyp its own context that the host will not see as a step towards a
full trust boundary between the two.
SP_EL0 and pointer authentication keys are currently shared between the
host and hyp so don't need to be switched yet.
Signed-off-by: Andrew Scull <ascull at google.com>
---
arch/arm64/kvm/hyp/include/hyp/switch.h | 2 +
arch/arm64/kvm/hyp/nvhe/Makefile | 2 +-
arch/arm64/kvm/hyp/nvhe/host.S | 68 ++++++++++++++++++-------
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 35 +++++++++++++
4 files changed, 88 insertions(+), 19 deletions(-)
create mode 100644 arch/arm64/kvm/hyp/nvhe/hyp-main.c
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 821721b78ad9..4536b50ddc06 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -372,6 +372,8 @@ static inline bool esr_is_ptrauth_trap(u32 esr)
ctxt_sys_reg(ctxt, key ## KEYHI_EL1) = __val; \
} while(0)
+DECLARE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
+
static inline bool __hyp_handle_ptrauth(struct kvm_vcpu *vcpu)
{
struct kvm_cpu_context *ctxt;
diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
index ddf98eb07b9d..46c89e8c30bc 100644
--- a/arch/arm64/kvm/hyp/nvhe/Makefile
+++ b/arch/arm64/kvm/hyp/nvhe/Makefile
@@ -6,7 +6,7 @@
asflags-y := -D__KVM_NVHE_HYPERVISOR__
ccflags-y := -D__KVM_NVHE_HYPERVISOR__
-obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o
+obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o hyp-main.o
obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
../fpsimd.o ../hyp-entry.o
diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S
index d4e8b8084020..1062547853db 100644
--- a/arch/arm64/kvm/hyp/nvhe/host.S
+++ b/arch/arm64/kvm/hyp/nvhe/host.S
@@ -12,6 +12,55 @@
.text
+SYM_FUNC_START(__host_exit)
+ stp x0, x1, [sp, #-16]!
+
+ get_host_ctxt x0, x1
+
+ ALTERNATIVE(nop, SET_PSTATE_PAN(1), ARM64_HAS_PAN, CONFIG_ARM64_PAN)
+
+ /* Store the guest regs x2 and x3 */
+ stp x2, x3, [x0, #CPU_XREG_OFFSET(2)]
+
+ /* Retrieve the guest regs x0-x1 from the stack */
+ ldp x2, x3, [sp], #16 // x0, x1
+
+ // Store the guest regs x0-x1 and x4-x17
+ stp x2, x3, [x0, #CPU_XREG_OFFSET(0)]
+ stp x4, x5, [x0, #CPU_XREG_OFFSET(4)]
+ stp x6, x7, [x0, #CPU_XREG_OFFSET(6)]
+ stp x8, x9, [x0, #CPU_XREG_OFFSET(8)]
+ stp x10, x11, [x0, #CPU_XREG_OFFSET(10)]
+ stp x12, x13, [x0, #CPU_XREG_OFFSET(12)]
+ stp x14, x15, [x0, #CPU_XREG_OFFSET(14)]
+ stp x16, x17, [x0, #CPU_XREG_OFFSET(16)]
+
+ /* Store the guest regs x18-x29, lr */
+ save_callee_saved_regs x0
+
+ /* Save the host context pointer in x29 across the function call */
+ mov x29, x0
+ bl handle_trap
+
+ /* Restore guest regs x0-x17 */
+ ldp x0, x1, [x29, #CPU_XREG_OFFSET(0)]
+ ldp x2, x3, [x29, #CPU_XREG_OFFSET(2)]
+ ldp x4, x5, [x29, #CPU_XREG_OFFSET(4)]
+ ldp x6, x7, [x29, #CPU_XREG_OFFSET(6)]
+ ldp x8, x9, [x29, #CPU_XREG_OFFSET(8)]
+ ldp x10, x11, [x29, #CPU_XREG_OFFSET(10)]
+ ldp x12, x13, [x29, #CPU_XREG_OFFSET(12)]
+ ldp x14, x15, [x29, #CPU_XREG_OFFSET(14)]
+ ldp x16, x17, [x29, #CPU_XREG_OFFSET(16)]
+
+ /* Restore guest regs x18-x29, lr */
+ restore_callee_saved_regs x29
+
+ /* Do not touch any register after this! */
+ eret
+ sb
+SYM_FUNC_END(__host_exit)
+
SYM_FUNC_START(__hyp_do_panic)
mov lr, #(PSR_F_BIT | PSR_I_BIT | PSR_A_BIT | PSR_D_BIT |\
PSR_MODE_EL1h)
@@ -35,7 +84,7 @@ SYM_FUNC_END(__hyp_do_panic)
/* Check for a stub HVC call */
cmp x0, #HVC_STUB_HCALL_NR
- b.hs 1f
+ b.hs __host_exit
/*
* Compute the idmap address of __kvm_handle_stub_hvc and
@@ -51,23 +100,6 @@ SYM_FUNC_END(__hyp_do_panic)
/* x5 = __pa(x5) */
sub x5, x5, x6
br x5
-
-1:
- /*
- * Shuffle the parameters before calling the function
- * pointed to in x0. Assumes parameters in x[1,2,3].
- */
- kern_hyp_va x0
- str lr, [sp, #-16]!
- mov lr, x0
- mov x0, x1
- mov x1, x2
- mov x2, x3
- blr lr
- ldr lr, [sp], #16
-
- eret
- sb
.endm
.macro invalid_host_vect
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
new file mode 100644
index 000000000000..c8938e09f585
--- /dev/null
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2020 - Google Inc
+ * Author: Andrew Scull <ascull at google.com>
+ */
+
+#include <hyp/switch.h>
+
+#include <asm/kvm_asm.h>
+#include <asm/kvm_emulate.h>
+#include <asm/kvm_host.h>
+#include <asm/kvm_hyp.h>
+#include <asm/kvm_mmu.h>
+
+typedef unsigned long (*hypcall_fn_t)
+ (unsigned long, unsigned long, unsigned long);
+
+void handle_trap(struct kvm_cpu_context *host_ctxt) {
+ u64 esr = read_sysreg_el2(SYS_ESR);
+ hypcall_fn_t func;
+ unsigned long ret;
+
+ if (ESR_ELx_EC(esr) != ESR_ELx_EC_HVC64)
+ hyp_panic();
+
+ /*
+ * __kvm_call_hyp takes a pointer in the host address space and
+ * up to three arguments.
+ */
+ func = (hypcall_fn_t)kern_hyp_va(host_ctxt->regs.regs[0]);
+ ret = func(host_ctxt->regs.regs[1],
+ host_ctxt->regs.regs[2],
+ host_ctxt->regs.regs[3]);
+ host_ctxt->regs.regs[0] = ret;
+}
--
2.28.0.402.g5ffc5be6b7-goog
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