From 4e3393a969a0bdaae83263918b6824b2d08c3996 Mon Sep 17 00:00:00 2001 From: Andrew Scull Date: Tue, 15 Sep 2020 11:46:36 +0100 Subject: [PATCH] KVM: arm64: nVHE: Switch to hyp context for EL2 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 Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20200915104643.2543892-13-ascull@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 | 36 +++++++++++++++++ 4 files changed, 89 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 821721b..4536b50 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 ddf98eb..46c89e8 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 9ab7814..d26e417 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 host regs x2 and x3 */ + stp x2, x3, [x0, #CPU_XREG_OFFSET(2)] + + /* Retrieve the host regs x0-x1 from the stack */ + ldp x2, x3, [sp], #16 // x0, x1 + + /* Store the host 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 host 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 host 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 host 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) @@ -34,7 +83,7 @@ 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 @@ -50,23 +99,6 @@ 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 .L__vect_end\@: .if ((.L__vect_end\@ - .L__vect_start\@) > 0x80) .error "host_el1_sync_vect larger than vector entry" 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 0000000..570c389 --- /dev/null +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -0,0 +1,36 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2020 - Google Inc + * Author: Andrew Scull + */ + +#include + +#include +#include +#include +#include +#include + +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; +} -- 2.7.4