From 1db9d9ded771389aae5760d20dd1bac113451b9c Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Wed, 21 Oct 2020 20:48:02 +0100 Subject: [PATCH 1/5] KVM: arm64: Add kimg_hyp_va() helper KVM/arm64 is so far unable to deal with function pointers, as the compiler will generate the kernel's runtime VA, and not the linear mapping address, meaning that kern_hyp_va() will give the wrong result. We so far have been able to use PC-relative addressing, but that's not always easy to use, and prevents the implementation of things like the mapping of an index to a pointer. To allow this, provide a new helper that computes the required translation from the kernel image to the HYP VA space. Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_mmu.h | 18 ++++++++++++ arch/arm64/kvm/va_layout.c | 50 ++++++++++++++++++++++++++++++++ 2 files changed, 68 insertions(+) diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index 331394306ccee..608c3a83e740d 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -98,6 +98,24 @@ static __always_inline unsigned long __kern_hyp_va(unsigned long v) #define kern_hyp_va(v) ((typeof(v))(__kern_hyp_va((unsigned long)(v)))) +static __always_inline unsigned long __kimg_hyp_va(unsigned long v) +{ + unsigned long offset; + + asm volatile(ALTERNATIVE_CB("movz %0, #0\n" + "movk %0, #0, lsl #16\n" + "movk %0, #0, lsl #32\n" + "movk %0, #0, lsl #48\n", + kvm_update_kimg_phys_offset) + : "=r" (offset)); + + return __kern_hyp_va((v - offset) | PAGE_OFFSET); +} + +#define kimg_fn_hyp_va(v) ((typeof(*v))(__kimg_hyp_va((unsigned long)(v)))) + +#define kimg_fn_ptr(x) (typeof(x) **)(x) + /* * We currently support using a VM-specified IPA size. For backward * compatibility, the default IPA size is fixed to 40bits. diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c index e0404bcab019a..1d00d2cb93fd5 100644 --- a/arch/arm64/kvm/va_layout.c +++ b/arch/arm64/kvm/va_layout.c @@ -11,6 +11,7 @@ #include #include #include +#include /* * The LSB of the HYP VA tag @@ -201,3 +202,52 @@ void kvm_patch_vector_branch(struct alt_instr *alt, AARCH64_INSN_BRANCH_NOLINK); *updptr++ = cpu_to_le32(insn); } + +static void generate_mov_q(u64 val, __le32 *origptr, __le32 *updptr, int nr_inst) +{ + u32 insn, oinsn, rd; + + BUG_ON(nr_inst != 4); + + /* Compute target register */ + oinsn = le32_to_cpu(*origptr); + rd = aarch64_insn_decode_register(AARCH64_INSN_REGTYPE_RD, oinsn); + + /* movz rd, #(val & 0xffff) */ + insn = aarch64_insn_gen_movewide(rd, + (u16)val, + 0, + AARCH64_INSN_VARIANT_64BIT, + AARCH64_INSN_MOVEWIDE_ZERO); + *updptr++ = cpu_to_le32(insn); + + /* movk rd, #((val >> 16) & 0xffff), lsl #16 */ + insn = aarch64_insn_gen_movewide(rd, + (u16)(val >> 16), + 16, + AARCH64_INSN_VARIANT_64BIT, + AARCH64_INSN_MOVEWIDE_KEEP); + *updptr++ = cpu_to_le32(insn); + + /* movk rd, #((val >> 32) & 0xffff), lsl #32 */ + insn = aarch64_insn_gen_movewide(rd, + (u16)(val >> 32), + 32, + AARCH64_INSN_VARIANT_64BIT, + AARCH64_INSN_MOVEWIDE_KEEP); + *updptr++ = cpu_to_le32(insn); + + /* movk rd, #((val >> 48) & 0xffff), lsl #48 */ + insn = aarch64_insn_gen_movewide(rd, + (u16)(val >> 48), + 48, + AARCH64_INSN_VARIANT_64BIT, + AARCH64_INSN_MOVEWIDE_KEEP); + *updptr++ = cpu_to_le32(insn); +} + +void kvm_update_kimg_phys_offset(struct alt_instr *alt, + __le32 *origptr, __le32 *updptr, int nr_inst) +{ + generate_mov_q(kimage_voffset + PHYS_OFFSET, origptr, updptr, nr_inst); +} From 7cd0aaafaadcaaf280887f8b478393a9fcfc69e3 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sun, 11 Oct 2020 18:17:38 +0100 Subject: [PATCH 2/5] KVM: arm64: Turn host HVC handling into a dispatch table Now that we can use function pointer, use a dispatch table to call the individual HVC handlers, leading to more maintainable code. Further improvements include helpers to declare the mapping of local variables to values passed in the host context. Reviewed-by: Alexandru Elisei Signed-off-by: Marc Zyngier --- arch/arm64/kernel/image-vars.h | 1 + arch/arm64/kvm/hyp/nvhe/hyp-main.c | 228 +++++++++++++++++------------ 2 files changed, 135 insertions(+), 94 deletions(-) diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h index c615b285ff5b3..e8c194f8de887 100644 --- a/arch/arm64/kernel/image-vars.h +++ b/arch/arm64/kernel/image-vars.h @@ -64,6 +64,7 @@ __efistub__ctype = _ctype; /* Alternative callbacks for init-time patching of nVHE hyp code. */ KVM_NVHE_ALIAS(kvm_patch_vector_branch); KVM_NVHE_ALIAS(kvm_update_va_mask); +KVM_NVHE_ALIAS(kvm_update_kimg_phys_offset); /* Global kernel state accessed by nVHE hyp code. */ KVM_NVHE_ALIAS(kvm_vgic_global_state); diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index e2eafe2c93aff..c0543b2e760ea 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -12,106 +12,146 @@ #include #include -#include - -static void handle_host_hcall(unsigned long func_id, - struct kvm_cpu_context *host_ctxt) -{ - unsigned long ret = 0; - - switch (func_id) { - case KVM_HOST_SMCCC_FUNC(__kvm_vcpu_run): { - unsigned long r1 = host_ctxt->regs.regs[1]; - struct kvm_vcpu *vcpu = (struct kvm_vcpu *)r1; - - ret = __kvm_vcpu_run(kern_hyp_va(vcpu)); - break; - } - case KVM_HOST_SMCCC_FUNC(__kvm_flush_vm_context): - __kvm_flush_vm_context(); - break; - case KVM_HOST_SMCCC_FUNC(__kvm_tlb_flush_vmid_ipa): { - unsigned long r1 = host_ctxt->regs.regs[1]; - struct kvm_s2_mmu *mmu = (struct kvm_s2_mmu *)r1; - phys_addr_t ipa = host_ctxt->regs.regs[2]; - int level = host_ctxt->regs.regs[3]; - - __kvm_tlb_flush_vmid_ipa(kern_hyp_va(mmu), ipa, level); - break; - } - case KVM_HOST_SMCCC_FUNC(__kvm_tlb_flush_vmid): { - unsigned long r1 = host_ctxt->regs.regs[1]; - struct kvm_s2_mmu *mmu = (struct kvm_s2_mmu *)r1; - - __kvm_tlb_flush_vmid(kern_hyp_va(mmu)); - break; - } - case KVM_HOST_SMCCC_FUNC(__kvm_tlb_flush_local_vmid): { - unsigned long r1 = host_ctxt->regs.regs[1]; - struct kvm_s2_mmu *mmu = (struct kvm_s2_mmu *)r1; - - __kvm_tlb_flush_local_vmid(kern_hyp_va(mmu)); - break; - } - case KVM_HOST_SMCCC_FUNC(__kvm_timer_set_cntvoff): { - u64 cntvoff = host_ctxt->regs.regs[1]; - - __kvm_timer_set_cntvoff(cntvoff); - break; - } - case KVM_HOST_SMCCC_FUNC(__kvm_enable_ssbs): - __kvm_enable_ssbs(); - break; - case KVM_HOST_SMCCC_FUNC(__vgic_v3_get_ich_vtr_el2): - ret = __vgic_v3_get_ich_vtr_el2(); - break; - case KVM_HOST_SMCCC_FUNC(__vgic_v3_read_vmcr): - ret = __vgic_v3_read_vmcr(); - break; - case KVM_HOST_SMCCC_FUNC(__vgic_v3_write_vmcr): { - u32 vmcr = host_ctxt->regs.regs[1]; - - __vgic_v3_write_vmcr(vmcr); - break; - } - case KVM_HOST_SMCCC_FUNC(__vgic_v3_init_lrs): - __vgic_v3_init_lrs(); - break; - case KVM_HOST_SMCCC_FUNC(__kvm_get_mdcr_el2): - ret = __kvm_get_mdcr_el2(); - break; - case KVM_HOST_SMCCC_FUNC(__vgic_v3_save_aprs): { - unsigned long r1 = host_ctxt->regs.regs[1]; - struct vgic_v3_cpu_if *cpu_if = (struct vgic_v3_cpu_if *)r1; - - __vgic_v3_save_aprs(kern_hyp_va(cpu_if)); - break; - } - case KVM_HOST_SMCCC_FUNC(__vgic_v3_restore_aprs): { - unsigned long r1 = host_ctxt->regs.regs[1]; - struct vgic_v3_cpu_if *cpu_if = (struct vgic_v3_cpu_if *)r1; - - __vgic_v3_restore_aprs(kern_hyp_va(cpu_if)); - break; - } - default: - /* Invalid host HVC. */ - host_ctxt->regs.regs[0] = SMCCC_RET_NOT_SUPPORTED; - return; - } - - host_ctxt->regs.regs[0] = SMCCC_RET_SUCCESS; - host_ctxt->regs.regs[1] = ret; +#define cpu_reg(ctxt, r) (ctxt)->regs.regs[r] +#define DECLARE_REG(type, name, ctxt, reg) \ + type name = (type)cpu_reg(ctxt, (reg)) + +static void handle___kvm_vcpu_run(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(struct kvm_vcpu *, vcpu, host_ctxt, 1); + + cpu_reg(host_ctxt, 1) = __kvm_vcpu_run(kern_hyp_va(vcpu)); +} + +static void handle___kvm_flush_vm_context(struct kvm_cpu_context *host_ctxt) +{ + __kvm_flush_vm_context(); +} + +static void handle___kvm_tlb_flush_vmid_ipa(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1); + DECLARE_REG(phys_addr_t, ipa, host_ctxt, 2); + DECLARE_REG(int, level, host_ctxt, 3); + + __kvm_tlb_flush_vmid_ipa(kern_hyp_va(mmu), ipa, level); +} + +static void handle___kvm_tlb_flush_vmid(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1); + + __kvm_tlb_flush_vmid(kern_hyp_va(mmu)); +} + +static void handle___kvm_tlb_flush_local_vmid(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(struct kvm_s2_mmu *, mmu, host_ctxt, 1); + + __kvm_tlb_flush_local_vmid(kern_hyp_va(mmu)); +} + +static void handle___kvm_timer_set_cntvoff(struct kvm_cpu_context *host_ctxt) +{ + __kvm_timer_set_cntvoff(cpu_reg(host_ctxt, 1)); +} + +static void handle___kvm_enable_ssbs(struct kvm_cpu_context *host_ctxt) +{ + __kvm_enable_ssbs(); +} + +static void handle___vgic_v3_get_ich_vtr_el2(struct kvm_cpu_context *host_ctxt) +{ + cpu_reg(host_ctxt, 1) = __vgic_v3_get_ich_vtr_el2(); +} + +static void handle___vgic_v3_read_vmcr(struct kvm_cpu_context *host_ctxt) +{ + cpu_reg(host_ctxt, 1) = __vgic_v3_read_vmcr(); +} + +static void handle___vgic_v3_write_vmcr(struct kvm_cpu_context *host_ctxt) +{ + __vgic_v3_write_vmcr(cpu_reg(host_ctxt, 1)); +} + +static void handle___vgic_v3_init_lrs(struct kvm_cpu_context *host_ctxt) +{ + __vgic_v3_init_lrs(); +} + +static void handle___kvm_get_mdcr_el2(struct kvm_cpu_context *host_ctxt) +{ + cpu_reg(host_ctxt, 1) = __kvm_get_mdcr_el2(); +} + +static void handle___vgic_v3_save_aprs(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(struct vgic_v3_cpu_if *, cpu_if, host_ctxt, 1); + + __vgic_v3_save_aprs(kern_hyp_va(cpu_if)); +} + +static void handle___vgic_v3_restore_aprs(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(struct vgic_v3_cpu_if *, cpu_if, host_ctxt, 1); + + __vgic_v3_restore_aprs(kern_hyp_va(cpu_if)); +} + +typedef void (*hcall_t)(struct kvm_cpu_context *); + +#define HANDLE_FUNC(x) [__KVM_HOST_SMCCC_FUNC_##x] = kimg_fn_ptr(handle_##x) + +static const hcall_t *host_hcall[] = { + HANDLE_FUNC(__kvm_vcpu_run), + HANDLE_FUNC(__kvm_flush_vm_context), + HANDLE_FUNC(__kvm_tlb_flush_vmid_ipa), + HANDLE_FUNC(__kvm_tlb_flush_vmid), + HANDLE_FUNC(__kvm_tlb_flush_local_vmid), + HANDLE_FUNC(__kvm_timer_set_cntvoff), + HANDLE_FUNC(__kvm_enable_ssbs), + HANDLE_FUNC(__vgic_v3_get_ich_vtr_el2), + HANDLE_FUNC(__vgic_v3_read_vmcr), + HANDLE_FUNC(__vgic_v3_write_vmcr), + HANDLE_FUNC(__vgic_v3_init_lrs), + HANDLE_FUNC(__kvm_get_mdcr_el2), + HANDLE_FUNC(__vgic_v3_save_aprs), + HANDLE_FUNC(__vgic_v3_restore_aprs), +}; + +static void handle_host_hcall(struct kvm_cpu_context *host_ctxt) +{ + DECLARE_REG(unsigned long, id, host_ctxt, 0); + const hcall_t *kfn; + hcall_t hfn; + + id -= KVM_HOST_SMCCC_ID(0); + + if (unlikely(id >= ARRAY_SIZE(host_hcall))) + goto inval; + + kfn = host_hcall[id]; + if (unlikely(!kfn)) + goto inval; + + cpu_reg(host_ctxt, 0) = SMCCC_RET_SUCCESS; + + hfn = kimg_fn_hyp_va(kfn); + hfn(host_ctxt); + + return; +inval: + cpu_reg(host_ctxt, 0) = SMCCC_RET_NOT_SUPPORTED; } void handle_trap(struct kvm_cpu_context *host_ctxt) { u64 esr = read_sysreg_el2(SYS_ESR); - unsigned long func_id; - if (ESR_ELx_EC(esr) != ESR_ELx_EC_HVC64) + if (unlikely(ESR_ELx_EC(esr) != ESR_ELx_EC_HVC64)) hyp_panic(); - func_id = host_ctxt->regs.regs[0]; - handle_host_hcall(func_id, host_ctxt); + handle_host_hcall(host_ctxt); } From 68b824e428c5fb5c3dc5ef80b1543e767534b58e Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sat, 24 Oct 2020 16:33:38 +0100 Subject: [PATCH 3/5] KVM: arm64: Patch kimage_voffset instead of loading the EL1 value Directly using the kimage_voffset variable is fine for now, but will become more problematic as we start distrusting EL1. Instead, patch the kimage_voffset into the HYP text, ensuring we don't have to load an untrusted value later on. Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_mmu.h | 22 ++++++++++++++++++++++ arch/arm64/kernel/image-vars.h | 4 +--- arch/arm64/kvm/hyp/nvhe/host.S | 5 +---- arch/arm64/kvm/va_layout.c | 6 ++++++ 4 files changed, 30 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h index 608c3a83e740d..5633c5a27aad3 100644 --- a/arch/arm64/include/asm/kvm_mmu.h +++ b/arch/arm64/include/asm/kvm_mmu.h @@ -72,6 +72,28 @@ alternative_cb kvm_update_va_mask alternative_cb_end .endm +/* + * Convert a kernel image address to a PA + * reg: kernel address to be converted in place + * tmp: temporary register + * + * The actual code generation takes place in kvm_get_kimage_voffset, and + * the instructions below are only there to reserve the space and + * perform the register allocation (kvm_get_kimage_voffset uses the + * specific registers encoded in the instructions). + */ +.macro kimg_pa reg, tmp +alternative_cb kvm_get_kimage_voffset + movz \tmp, #0 + movk \tmp, #0, lsl #16 + movk \tmp, #0, lsl #32 + movk \tmp, #0, lsl #48 +alternative_cb_end + + /* reg = __pa(reg) */ + sub \reg, \reg, \tmp +.endm + #else #include diff --git a/arch/arm64/kernel/image-vars.h b/arch/arm64/kernel/image-vars.h index e8c194f8de887..4b32588918d90 100644 --- a/arch/arm64/kernel/image-vars.h +++ b/arch/arm64/kernel/image-vars.h @@ -65,13 +65,11 @@ __efistub__ctype = _ctype; KVM_NVHE_ALIAS(kvm_patch_vector_branch); KVM_NVHE_ALIAS(kvm_update_va_mask); KVM_NVHE_ALIAS(kvm_update_kimg_phys_offset); +KVM_NVHE_ALIAS(kvm_get_kimage_voffset); /* Global kernel state accessed by nVHE hyp code. */ KVM_NVHE_ALIAS(kvm_vgic_global_state); -/* Kernel constant needed to compute idmap addresses. */ -KVM_NVHE_ALIAS(kimage_voffset); - /* Kernel symbols used to call panic() from nVHE hyp code (via ERET). */ KVM_NVHE_ALIAS(__hyp_panic_string); KVM_NVHE_ALIAS(panic); diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S index ed27f06a31ba2..4e207c1c51267 100644 --- a/arch/arm64/kvm/hyp/nvhe/host.S +++ b/arch/arm64/kvm/hyp/nvhe/host.S @@ -115,10 +115,7 @@ SYM_FUNC_END(__hyp_do_panic) * Preserve x0-x4, which may contain stub parameters. */ ldr x5, =__kvm_handle_stub_hvc - ldr_l x6, kimage_voffset - - /* x5 = __pa(x5) */ - sub x5, x5, x6 + kimg_pa x5, x6 br x5 .L__vect_end\@: .if ((.L__vect_end\@ - .L__vect_start\@) > 0x80) diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c index 1d00d2cb93fd5..d61117805de06 100644 --- a/arch/arm64/kvm/va_layout.c +++ b/arch/arm64/kvm/va_layout.c @@ -251,3 +251,9 @@ void kvm_update_kimg_phys_offset(struct alt_instr *alt, { generate_mov_q(kimage_voffset + PHYS_OFFSET, origptr, updptr, nr_inst); } + +void kvm_get_kimage_voffset(struct alt_instr *alt, + __le32 *origptr, __le32 *updptr, int nr_inst) +{ + generate_mov_q(kimage_voffset, origptr, updptr, nr_inst); +} From 29052f1b92f2bcb0419c544459f4c919bfb20898 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Wed, 21 Oct 2020 21:52:54 +0100 Subject: [PATCH 4/5] KVM: arm64: Simplify __kvm_enable_ssbs() Move the setting of SSBS directly into the HVC handler, using the C helpers rather than the inline asssembly code. Reviewed-by: Alexandru Elisei Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_asm.h | 2 -- arch/arm64/include/asm/sysreg.h | 1 + arch/arm64/kvm/hyp/nvhe/hyp-main.c | 6 +++++- arch/arm64/kvm/hyp/nvhe/sysreg-sr.c | 11 ----------- 4 files changed, 6 insertions(+), 14 deletions(-) diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 54387ccd1ab26..a542c422a036f 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -189,8 +189,6 @@ extern void __kvm_timer_set_cntvoff(u64 cntvoff); extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu); -extern void __kvm_enable_ssbs(void); - extern u64 __vgic_v3_get_ich_vtr_el2(void); extern u64 __vgic_v3_read_vmcr(void); extern void __vgic_v3_write_vmcr(u32 vmcr); diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index 174817ba119cb..153faa15d4909 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -461,6 +461,7 @@ #define SYS_PMCCFILTR_EL0 sys_reg(3, 3, 14, 15, 7) +#define SYS_SCTLR_EL2 sys_reg(3, 4, 1, 0, 0) #define SYS_ZCR_EL2 sys_reg(3, 4, 1, 2, 0) #define SYS_DACR32_EL2 sys_reg(3, 4, 3, 0, 0) #define SYS_SPSR_EL2 sys_reg(3, 4, 4, 0, 0) diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index c0543b2e760ea..82df7fc247606 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -58,7 +58,11 @@ static void handle___kvm_timer_set_cntvoff(struct kvm_cpu_context *host_ctxt) static void handle___kvm_enable_ssbs(struct kvm_cpu_context *host_ctxt) { - __kvm_enable_ssbs(); + u64 tmp; + + tmp = read_sysreg_el2(SYS_SCTLR); + tmp |= SCTLR_ELx_DSSBS; + write_sysreg_el2(tmp, SYS_SCTLR); } static void handle___vgic_v3_get_ich_vtr_el2(struct kvm_cpu_context *host_ctxt) diff --git a/arch/arm64/kvm/hyp/nvhe/sysreg-sr.c b/arch/arm64/kvm/hyp/nvhe/sysreg-sr.c index 88a25fc8fcd36..29305022bc048 100644 --- a/arch/arm64/kvm/hyp/nvhe/sysreg-sr.c +++ b/arch/arm64/kvm/hyp/nvhe/sysreg-sr.c @@ -33,14 +33,3 @@ void __sysreg_restore_state_nvhe(struct kvm_cpu_context *ctxt) __sysreg_restore_user_state(ctxt); __sysreg_restore_el2_return_state(ctxt); } - -void __kvm_enable_ssbs(void) -{ - u64 tmp; - - asm volatile( - "mrs %0, sctlr_el2\n" - "orr %0, %0, %1\n" - "msr sctlr_el2, %0" - : "=&r" (tmp) : "L" (SCTLR_ELx_DSSBS)); -} From 83fa381f66ccb025f9e182d0b2ef9cd53c1f33ab Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Sat, 24 Oct 2020 10:56:55 +0100 Subject: [PATCH 5/5] KVM: arm64: Avoid repetitive stack access on host EL1 to EL2 exception Registers x0/x1 get repeateadly pushed and poped during a host HVC call. Instead, leave the registers on the stack, trading a store instruction on the fast path for an add on the slow path. Reviewed-by: Alexandru Elisei Signed-off-by: Marc Zyngier --- arch/arm64/kvm/hyp/nvhe/host.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S index 4e207c1c51267..fe2740b224cf0 100644 --- a/arch/arm64/kvm/hyp/nvhe/host.S +++ b/arch/arm64/kvm/hyp/nvhe/host.S @@ -13,8 +13,6 @@ .text SYM_FUNC_START(__host_exit) - stp x0, x1, [sp, #-16]! - get_host_ctxt x0, x1 /* Store the host regs x2 and x3 */ @@ -99,13 +97,15 @@ SYM_FUNC_END(__hyp_do_panic) mrs x0, esr_el2 lsr x0, x0, #ESR_ELx_EC_SHIFT cmp x0, #ESR_ELx_EC_HVC64 - ldp x0, x1, [sp], #16 b.ne __host_exit + ldp x0, x1, [sp] // Don't fixup the stack yet + /* Check for a stub HVC call */ cmp x0, #HVC_STUB_HCALL_NR b.hs __host_exit + add sp, sp, #16 /* * Compute the idmap address of __kvm_handle_stub_hvc and * jump there. Since we use kimage_voffset, do not use the