KVM: ARM: World-switch implementation
Provides complete world-switch implementation to switch to other guests
running in non-secure modes. Includes Hyp exception handlers that
capture necessary exception information and stores the information on
the VCPU and KVM structures.
The following Hyp-ABI is also documented in the code:
Hyp-ABI: Calling HYP-mode functions from host (in SVC mode):
Switching to Hyp mode is done through a simple HVC #0 instruction. The
exception vector code will check that the HVC comes from VMID==0 and if
so will push the necessary state (SPSR, lr_usr) on the Hyp stack.
- r0 contains a pointer to a HYP function
- r1, r2, and r3 contain arguments to the above function.
- The HYP function will be called with its arguments in r0, r1 and r2.
On HYP function return, we return directly to SVC.
A call to a function executing in Hyp mode is performed like the following:
<svc code>
ldr r0, =BSYM(my_hyp_fn)
ldr r1, =my_param
hvc #0 ; Call my_hyp_fn(my_param) from HYP mode
<svc code>
Otherwise, the world-switch is pretty straight-forward. All state that
can be modified by the guest is first backed up on the Hyp stack and the
VCPU values is loaded onto the hardware. State, which is not loaded, but
theoretically modifiable by the guest is protected through the
virtualiation features to generate a trap and cause software emulation.
Upon guest returns, all state is restored from hardware onto the VCPU
struct and the original state is restored from the Hyp-stack onto the
hardware.
SMP support using the VMPIDR calculated on the basis of the host MPIDR
and overriding the low bits with KVM vcpu_id contributed by Marc Zyngier.
Reuse of VMIDs has been implemented by Antonios Motakis and adapated from
a separate patch into the appropriate patches introducing the
functionality. Note that the VMIDs are stored per VM as required by the ARM
architecture reference manual.
To support VFP/NEON we trap those instructions using the HPCTR. When
we trap, we switch the FPU. After a guest exit, the VFP state is
returned to the host. When disabling access to floating point
instructions, we also mask FPEXC_EN in order to avoid the guest
receiving Undefined instruction exceptions before we have a chance to
switch back the floating point state. We are reusing vfp_hard_struct,
so we depend on VFPv3 being enabled in the host kernel, if not, we still
trap cp10 and cp11 in order to inject an undefined instruction exception
whenever the guest tries to use VFP/NEON. VFP/NEON developed by
Antionios Motakis and Rusty Russell.
Aborts that are permission faults, and not stage-1 page table walk, do
not report the faulting address in the HPFAR. We have to resolve the
IPA, and store it just like the HPFAR register on the VCPU struct. If
the IPA cannot be resolved, it means another CPU is playing with the
page tables, and we simply restart the guest. This quirk was fixed by
Marc Zyngier.
Reviewed-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
new file mode 100644
index 0000000..6a95d34
--- /dev/null
+++ b/arch/arm/kvm/interrupts_head.S
@@ -0,0 +1,441 @@
+#define VCPU_USR_REG(_reg_nr) (VCPU_USR_REGS + (_reg_nr * 4))
+#define VCPU_USR_SP (VCPU_USR_REG(13))
+#define VCPU_USR_LR (VCPU_USR_REG(14))
+#define CP15_OFFSET(_cp15_reg_idx) (VCPU_CP15 + (_cp15_reg_idx * 4))
+
+/*
+ * Many of these macros need to access the VCPU structure, which is always
+ * held in r0. These macros should never clobber r1, as it is used to hold the
+ * exception code on the return path (except of course the macro that switches
+ * all the registers before the final jump to the VM).
+ */
+vcpu .req r0 @ vcpu pointer always in r0
+
+/* Clobbers {r2-r6} */
+.macro store_vfp_state vfp_base
+ @ The VFPFMRX and VFPFMXR macros are the VMRS and VMSR instructions
+ VFPFMRX r2, FPEXC
+ @ Make sure VFP is enabled so we can touch the registers.
+ orr r6, r2, #FPEXC_EN
+ VFPFMXR FPEXC, r6
+
+ VFPFMRX r3, FPSCR
+ tst r2, #FPEXC_EX @ Check for VFP Subarchitecture
+ beq 1f
+ @ If FPEXC_EX is 0, then FPINST/FPINST2 reads are upredictable, so
+ @ we only need to save them if FPEXC_EX is set.
+ VFPFMRX r4, FPINST
+ tst r2, #FPEXC_FP2V
+ VFPFMRX r5, FPINST2, ne @ vmrsne
+ bic r6, r2, #FPEXC_EX @ FPEXC_EX disable
+ VFPFMXR FPEXC, r6
+1:
+ VFPFSTMIA \vfp_base, r6 @ Save VFP registers
+ stm \vfp_base, {r2-r5} @ Save FPEXC, FPSCR, FPINST, FPINST2
+.endm
+
+/* Assume FPEXC_EN is on and FPEXC_EX is off, clobbers {r2-r6} */
+.macro restore_vfp_state vfp_base
+ VFPFLDMIA \vfp_base, r6 @ Load VFP registers
+ ldm \vfp_base, {r2-r5} @ Load FPEXC, FPSCR, FPINST, FPINST2
+
+ VFPFMXR FPSCR, r3
+ tst r2, #FPEXC_EX @ Check for VFP Subarchitecture
+ beq 1f
+ VFPFMXR FPINST, r4
+ tst r2, #FPEXC_FP2V
+ VFPFMXR FPINST2, r5, ne
+1:
+ VFPFMXR FPEXC, r2 @ FPEXC (last, in case !EN)
+.endm
+
+/* These are simply for the macros to work - value don't have meaning */
+.equ usr, 0
+.equ svc, 1
+.equ abt, 2
+.equ und, 3
+.equ irq, 4
+.equ fiq, 5
+
+.macro push_host_regs_mode mode
+ mrs r2, SP_\mode
+ mrs r3, LR_\mode
+ mrs r4, SPSR_\mode
+ push {r2, r3, r4}
+.endm
+
+/*
+ * Store all host persistent registers on the stack.
+ * Clobbers all registers, in all modes, except r0 and r1.
+ */
+.macro save_host_regs
+ /* Hyp regs. Only ELR_hyp (SPSR_hyp already saved) */
+ mrs r2, ELR_hyp
+ push {r2}
+
+ /* usr regs */
+ push {r4-r12} @ r0-r3 are always clobbered
+ mrs r2, SP_usr
+ mov r3, lr
+ push {r2, r3}
+
+ push_host_regs_mode svc
+ push_host_regs_mode abt
+ push_host_regs_mode und
+ push_host_regs_mode irq
+
+ /* fiq regs */
+ mrs r2, r8_fiq
+ mrs r3, r9_fiq
+ mrs r4, r10_fiq
+ mrs r5, r11_fiq
+ mrs r6, r12_fiq
+ mrs r7, SP_fiq
+ mrs r8, LR_fiq
+ mrs r9, SPSR_fiq
+ push {r2-r9}
+.endm
+
+.macro pop_host_regs_mode mode
+ pop {r2, r3, r4}
+ msr SP_\mode, r2
+ msr LR_\mode, r3
+ msr SPSR_\mode, r4
+.endm
+
+/*
+ * Restore all host registers from the stack.
+ * Clobbers all registers, in all modes, except r0 and r1.
+ */
+.macro restore_host_regs
+ pop {r2-r9}
+ msr r8_fiq, r2
+ msr r9_fiq, r3
+ msr r10_fiq, r4
+ msr r11_fiq, r5
+ msr r12_fiq, r6
+ msr SP_fiq, r7
+ msr LR_fiq, r8
+ msr SPSR_fiq, r9
+
+ pop_host_regs_mode irq
+ pop_host_regs_mode und
+ pop_host_regs_mode abt
+ pop_host_regs_mode svc
+
+ pop {r2, r3}
+ msr SP_usr, r2
+ mov lr, r3
+ pop {r4-r12}
+
+ pop {r2}
+ msr ELR_hyp, r2
+.endm
+
+/*
+ * Restore SP, LR and SPSR for a given mode. offset is the offset of
+ * this mode's registers from the VCPU base.
+ *
+ * Assumes vcpu pointer in vcpu reg
+ *
+ * Clobbers r1, r2, r3, r4.
+ */
+.macro restore_guest_regs_mode mode, offset
+ add r1, vcpu, \offset
+ ldm r1, {r2, r3, r4}
+ msr SP_\mode, r2
+ msr LR_\mode, r3
+ msr SPSR_\mode, r4
+.endm
+
+/*
+ * Restore all guest registers from the vcpu struct.
+ *
+ * Assumes vcpu pointer in vcpu reg
+ *
+ * Clobbers *all* registers.
+ */
+.macro restore_guest_regs
+ restore_guest_regs_mode svc, #VCPU_SVC_REGS
+ restore_guest_regs_mode abt, #VCPU_ABT_REGS
+ restore_guest_regs_mode und, #VCPU_UND_REGS
+ restore_guest_regs_mode irq, #VCPU_IRQ_REGS
+
+ add r1, vcpu, #VCPU_FIQ_REGS
+ ldm r1, {r2-r9}
+ msr r8_fiq, r2
+ msr r9_fiq, r3
+ msr r10_fiq, r4
+ msr r11_fiq, r5
+ msr r12_fiq, r6
+ msr SP_fiq, r7
+ msr LR_fiq, r8
+ msr SPSR_fiq, r9
+
+ @ Load return state
+ ldr r2, [vcpu, #VCPU_PC]
+ ldr r3, [vcpu, #VCPU_CPSR]
+ msr ELR_hyp, r2
+ msr SPSR_cxsf, r3
+
+ @ Load user registers
+ ldr r2, [vcpu, #VCPU_USR_SP]
+ ldr r3, [vcpu, #VCPU_USR_LR]
+ msr SP_usr, r2
+ mov lr, r3
+ add vcpu, vcpu, #(VCPU_USR_REGS)
+ ldm vcpu, {r0-r12}
+.endm
+
+/*
+ * Save SP, LR and SPSR for a given mode. offset is the offset of
+ * this mode's registers from the VCPU base.
+ *
+ * Assumes vcpu pointer in vcpu reg
+ *
+ * Clobbers r2, r3, r4, r5.
+ */
+.macro save_guest_regs_mode mode, offset
+ add r2, vcpu, \offset
+ mrs r3, SP_\mode
+ mrs r4, LR_\mode
+ mrs r5, SPSR_\mode
+ stm r2, {r3, r4, r5}
+.endm
+
+/*
+ * Save all guest registers to the vcpu struct
+ * Expects guest's r0, r1, r2 on the stack.
+ *
+ * Assumes vcpu pointer in vcpu reg
+ *
+ * Clobbers r2, r3, r4, r5.
+ */
+.macro save_guest_regs
+ @ Store usr registers
+ add r2, vcpu, #VCPU_USR_REG(3)
+ stm r2, {r3-r12}
+ add r2, vcpu, #VCPU_USR_REG(0)
+ pop {r3, r4, r5} @ r0, r1, r2
+ stm r2, {r3, r4, r5}
+ mrs r2, SP_usr
+ mov r3, lr
+ str r2, [vcpu, #VCPU_USR_SP]
+ str r3, [vcpu, #VCPU_USR_LR]
+
+ @ Store return state
+ mrs r2, ELR_hyp
+ mrs r3, spsr
+ str r2, [vcpu, #VCPU_PC]
+ str r3, [vcpu, #VCPU_CPSR]
+
+ @ Store other guest registers
+ save_guest_regs_mode svc, #VCPU_SVC_REGS
+ save_guest_regs_mode abt, #VCPU_ABT_REGS
+ save_guest_regs_mode und, #VCPU_UND_REGS
+ save_guest_regs_mode irq, #VCPU_IRQ_REGS
+.endm
+
+/* Reads cp15 registers from hardware and stores them in memory
+ * @store_to_vcpu: If 0, registers are written in-order to the stack,
+ * otherwise to the VCPU struct pointed to by vcpup
+ *
+ * Assumes vcpu pointer in vcpu reg
+ *
+ * Clobbers r2 - r12
+ */
+.macro read_cp15_state store_to_vcpu
+ mrc p15, 0, r2, c1, c0, 0 @ SCTLR
+ mrc p15, 0, r3, c1, c0, 2 @ CPACR
+ mrc p15, 0, r4, c2, c0, 2 @ TTBCR
+ mrc p15, 0, r5, c3, c0, 0 @ DACR
+ mrrc p15, 0, r6, r7, c2 @ TTBR 0
+ mrrc p15, 1, r8, r9, c2 @ TTBR 1
+ mrc p15, 0, r10, c10, c2, 0 @ PRRR
+ mrc p15, 0, r11, c10, c2, 1 @ NMRR
+ mrc p15, 2, r12, c0, c0, 0 @ CSSELR
+
+ .if \store_to_vcpu == 0
+ push {r2-r12} @ Push CP15 registers
+ .else
+ str r2, [vcpu, #CP15_OFFSET(c1_SCTLR)]
+ str r3, [vcpu, #CP15_OFFSET(c1_CPACR)]
+ str r4, [vcpu, #CP15_OFFSET(c2_TTBCR)]
+ str r5, [vcpu, #CP15_OFFSET(c3_DACR)]
+ add r2, vcpu, #CP15_OFFSET(c2_TTBR0)
+ strd r6, r7, [r2]
+ add r2, vcpu, #CP15_OFFSET(c2_TTBR1)
+ strd r8, r9, [r2]
+ str r10, [vcpu, #CP15_OFFSET(c10_PRRR)]
+ str r11, [vcpu, #CP15_OFFSET(c10_NMRR)]
+ str r12, [vcpu, #CP15_OFFSET(c0_CSSELR)]
+ .endif
+
+ mrc p15, 0, r2, c13, c0, 1 @ CID
+ mrc p15, 0, r3, c13, c0, 2 @ TID_URW
+ mrc p15, 0, r4, c13, c0, 3 @ TID_URO
+ mrc p15, 0, r5, c13, c0, 4 @ TID_PRIV
+ mrc p15, 0, r6, c5, c0, 0 @ DFSR
+ mrc p15, 0, r7, c5, c0, 1 @ IFSR
+ mrc p15, 0, r8, c5, c1, 0 @ ADFSR
+ mrc p15, 0, r9, c5, c1, 1 @ AIFSR
+ mrc p15, 0, r10, c6, c0, 0 @ DFAR
+ mrc p15, 0, r11, c6, c0, 2 @ IFAR
+ mrc p15, 0, r12, c12, c0, 0 @ VBAR
+
+ .if \store_to_vcpu == 0
+ push {r2-r12} @ Push CP15 registers
+ .else
+ str r2, [vcpu, #CP15_OFFSET(c13_CID)]
+ str r3, [vcpu, #CP15_OFFSET(c13_TID_URW)]
+ str r4, [vcpu, #CP15_OFFSET(c13_TID_URO)]
+ str r5, [vcpu, #CP15_OFFSET(c13_TID_PRIV)]
+ str r6, [vcpu, #CP15_OFFSET(c5_DFSR)]
+ str r7, [vcpu, #CP15_OFFSET(c5_IFSR)]
+ str r8, [vcpu, #CP15_OFFSET(c5_ADFSR)]
+ str r9, [vcpu, #CP15_OFFSET(c5_AIFSR)]
+ str r10, [vcpu, #CP15_OFFSET(c6_DFAR)]
+ str r11, [vcpu, #CP15_OFFSET(c6_IFAR)]
+ str r12, [vcpu, #CP15_OFFSET(c12_VBAR)]
+ .endif
+.endm
+
+/*
+ * Reads cp15 registers from memory and writes them to hardware
+ * @read_from_vcpu: If 0, registers are read in-order from the stack,
+ * otherwise from the VCPU struct pointed to by vcpup
+ *
+ * Assumes vcpu pointer in vcpu reg
+ */
+.macro write_cp15_state read_from_vcpu
+ .if \read_from_vcpu == 0
+ pop {r2-r12}
+ .else
+ ldr r2, [vcpu, #CP15_OFFSET(c13_CID)]
+ ldr r3, [vcpu, #CP15_OFFSET(c13_TID_URW)]
+ ldr r4, [vcpu, #CP15_OFFSET(c13_TID_URO)]
+ ldr r5, [vcpu, #CP15_OFFSET(c13_TID_PRIV)]
+ ldr r6, [vcpu, #CP15_OFFSET(c5_DFSR)]
+ ldr r7, [vcpu, #CP15_OFFSET(c5_IFSR)]
+ ldr r8, [vcpu, #CP15_OFFSET(c5_ADFSR)]
+ ldr r9, [vcpu, #CP15_OFFSET(c5_AIFSR)]
+ ldr r10, [vcpu, #CP15_OFFSET(c6_DFAR)]
+ ldr r11, [vcpu, #CP15_OFFSET(c6_IFAR)]
+ ldr r12, [vcpu, #CP15_OFFSET(c12_VBAR)]
+ .endif
+
+ mcr p15, 0, r2, c13, c0, 1 @ CID
+ mcr p15, 0, r3, c13, c0, 2 @ TID_URW
+ mcr p15, 0, r4, c13, c0, 3 @ TID_URO
+ mcr p15, 0, r5, c13, c0, 4 @ TID_PRIV
+ mcr p15, 0, r6, c5, c0, 0 @ DFSR
+ mcr p15, 0, r7, c5, c0, 1 @ IFSR
+ mcr p15, 0, r8, c5, c1, 0 @ ADFSR
+ mcr p15, 0, r9, c5, c1, 1 @ AIFSR
+ mcr p15, 0, r10, c6, c0, 0 @ DFAR
+ mcr p15, 0, r11, c6, c0, 2 @ IFAR
+ mcr p15, 0, r12, c12, c0, 0 @ VBAR
+
+ .if \read_from_vcpu == 0
+ pop {r2-r12}
+ .else
+ ldr r2, [vcpu, #CP15_OFFSET(c1_SCTLR)]
+ ldr r3, [vcpu, #CP15_OFFSET(c1_CPACR)]
+ ldr r4, [vcpu, #CP15_OFFSET(c2_TTBCR)]
+ ldr r5, [vcpu, #CP15_OFFSET(c3_DACR)]
+ add r12, vcpu, #CP15_OFFSET(c2_TTBR0)
+ ldrd r6, r7, [r12]
+ add r12, vcpu, #CP15_OFFSET(c2_TTBR1)
+ ldrd r8, r9, [r12]
+ ldr r10, [vcpu, #CP15_OFFSET(c10_PRRR)]
+ ldr r11, [vcpu, #CP15_OFFSET(c10_NMRR)]
+ ldr r12, [vcpu, #CP15_OFFSET(c0_CSSELR)]
+ .endif
+
+ mcr p15, 0, r2, c1, c0, 0 @ SCTLR
+ mcr p15, 0, r3, c1, c0, 2 @ CPACR
+ mcr p15, 0, r4, c2, c0, 2 @ TTBCR
+ mcr p15, 0, r5, c3, c0, 0 @ DACR
+ mcrr p15, 0, r6, r7, c2 @ TTBR 0
+ mcrr p15, 1, r8, r9, c2 @ TTBR 1
+ mcr p15, 0, r10, c10, c2, 0 @ PRRR
+ mcr p15, 0, r11, c10, c2, 1 @ NMRR
+ mcr p15, 2, r12, c0, c0, 0 @ CSSELR
+.endm
+
+/*
+ * Save the VGIC CPU state into memory
+ *
+ * Assumes vcpu pointer in vcpu reg
+ */
+.macro save_vgic_state
+.endm
+
+/*
+ * Restore the VGIC CPU state from memory
+ *
+ * Assumes vcpu pointer in vcpu reg
+ */
+.macro restore_vgic_state
+.endm
+
+.equ vmentry, 0
+.equ vmexit, 1
+
+/* Configures the HSTR (Hyp System Trap Register) on entry/return
+ * (hardware reset value is 0) */
+.macro set_hstr operation
+ mrc p15, 4, r2, c1, c1, 3
+ ldr r3, =HSTR_T(15)
+ .if \operation == vmentry
+ orr r2, r2, r3 @ Trap CR{15}
+ .else
+ bic r2, r2, r3 @ Don't trap any CRx accesses
+ .endif
+ mcr p15, 4, r2, c1, c1, 3
+.endm
+
+/* Configures the HCPTR (Hyp Coprocessor Trap Register) on entry/return
+ * (hardware reset value is 0). Keep previous value in r2. */
+.macro set_hcptr operation, mask
+ mrc p15, 4, r2, c1, c1, 2
+ ldr r3, =\mask
+ .if \operation == vmentry
+ orr r3, r2, r3 @ Trap coproc-accesses defined in mask
+ .else
+ bic r3, r2, r3 @ Don't trap defined coproc-accesses
+ .endif
+ mcr p15, 4, r3, c1, c1, 2
+.endm
+
+/* Configures the HDCR (Hyp Debug Configuration Register) on entry/return
+ * (hardware reset value is 0) */
+.macro set_hdcr operation
+ mrc p15, 4, r2, c1, c1, 1
+ ldr r3, =(HDCR_TPM|HDCR_TPMCR)
+ .if \operation == vmentry
+ orr r2, r2, r3 @ Trap some perfmon accesses
+ .else
+ bic r2, r2, r3 @ Don't trap any perfmon accesses
+ .endif
+ mcr p15, 4, r2, c1, c1, 1
+.endm
+
+/* Enable/Disable: stage-2 trans., trap interrupts, trap wfi, trap smc */
+.macro configure_hyp_role operation
+ mrc p15, 4, r2, c1, c1, 0 @ HCR
+ bic r2, r2, #HCR_VIRT_EXCP_MASK
+ ldr r3, =HCR_GUEST_MASK
+ .if \operation == vmentry
+ orr r2, r2, r3
+ ldr r3, [vcpu, #VCPU_IRQ_LINES]
+ orr r2, r2, r3
+ .else
+ bic r2, r2, r3
+ .endif
+ mcr p15, 4, r2, c1, c1, 0
+.endm
+
+.macro load_vcpu
+ mrc p15, 4, vcpu, c13, c0, 2 @ HTPIDR
+.endm