With VHE enabled, it is possible to let the kernel handle an interrupt
without saving the full guest context, and without restoring the full
host context either. This reduces the latency of handling an interrupt.
When an interrupt fires we can:
- save the guest's general purpose registers, shared system registers
and timer state
- switch to a host context (setting vectors, deactivating traps and
stage-2 translation)
- restore the host's shared sysregs
At that stage, we're able to jump to the interrupt handler.
On return from the handler, we can finish the switch (save/restore
whatever is missing from the above).
Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
---
arch/arm/kvm/arm.c | 3 +++
arch/arm64/kvm/hyp.S | 56 ++++++++++++++++++++++++++++++++++++++---
arch/arm64/kvm/vgic-v2-switch.S | 19 +++++++++++---
arch/arm64/kvm/vgic-v3-switch.S | 33 +++++++++++++-----------
4 files changed, 90 insertions(+), 21 deletions(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index ca3c662..ab9333f 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -573,6 +573,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct
kvm_run *run)
* disabled. Enabling the interrupts now will have
* the effect of taking the interrupt again, in SVC
* mode this time.
+ *
+ * With VHE, the interrupt is likely to have been
+ * already taken already.
*/
local_irq_enable();
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index 3cbd2c4..ac95ba3 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -714,8 +714,10 @@ skip_el1_restore:
.endm
.macro skip_32bit_state tmp, target
- // Skip 32bit state if not needed
- mrs \tmp, hcr_el2
+ // Skip 32bit state if not needed.
+ // With VHE, we may have cleared the RW bit in HCR_EL2 early,
+ // and have to rely on the memory version instead.
+ifnvhe "mrs \tmp, hcr_el2", _S_(ldr \tmp, [x0,
#VCPU_HCR_EL2])
tbnz \tmp, #HCR_RW_SHIFT, \target
.endm
@@ -1053,11 +1055,18 @@ __kvm_vcpu_return:
save_guest_32bit_state
save_timer_state
+ifnvhe "b 1f", nop
+ alternative_insn "bl __vgic_v2_disable", \
+ "bl __vgic_v3_disable", \
+ ARM64_HAS_SYSREG_GIC_CPUIF
+1:
save_vgic_state
deactivate_traps
deactivate_vm
+__kvm_vcpu_return_irq:
+
// Host context
ldr x2, [x0, #VCPU_HOST_CONTEXT]
kern_hyp_va x2
@@ -1355,8 +1364,47 @@ el1_irq:
push x0, x1
push x2, x3
mrs x0, tpidr_el2
- mov x1, #ARM_EXCEPTION_IRQ
- b __kvm_vcpu_return
+ifnvhe _S_(mov x1, #ARM_EXCEPTION_IRQ), nop
+ifnvhe "b __kvm_vcpu_return", nop
+
+ // Fallthrough for VHE
+ add x2, x0, #VCPU_CONTEXT
+
+ save_guest_regs
+ bl __save_shared_sysregs
+ save_timer_state
+ alternative_insn "bl __vgic_v2_disable", \
+ "bl __vgic_v3_disable", \
+ ARM64_HAS_SYSREG_GIC_CPUIF
+ deactivate_traps
+ deactivate_vm
+
+ isb // Needed to ensure TGE is on and vectors have been switched
+
+ ldr x2, [x0, #VCPU_HOST_CONTEXT]
+ restore_shared_sysregs
+
+ mov x0, x2
+ adrp x1, handle_arch_irq
+ add x1, x1, #:lo12:handle_arch_irq
+ ldr x1, [x1]
+ blr x1
+
+ // Back from the interrupt handler, finalize the world switch
+ mrs x0, tpidr_el2
+ add x2, x0, #VCPU_CONTEXT
+
+ bl __save_fpsimd
+ bl __save_sysregs // We've already saved the shared regs
+ save_guest_32bit_state
+
+ skip_debug_state x3, 1f
+ bl __save_debug
+1:
+ save_vgic_state
+
+ mov x1, #ARM_EXCEPTION_IRQ
+ b __kvm_vcpu_return_irq
.ltorg
diff --git a/arch/arm64/kvm/vgic-v2-switch.S b/arch/arm64/kvm/vgic-v2-switch.S
index 3f00071..c8864b4 100644
--- a/arch/arm64/kvm/vgic-v2-switch.S
+++ b/arch/arm64/kvm/vgic-v2-switch.S
@@ -26,16 +26,30 @@
#include <asm/kvm_arm.h>
#include <asm/kvm_mmu.h>
+#include "vhe-macros.h"
+
.text
.pushsection .hyp.text, "ax"
+ENTRY(__vgic_v2_disable)
+ /* Get VGIC VCTRL base into x2 */
+ ldr x2, [x0, #VCPU_KVM]
+ kern_hyp_va x2
+ ldr x2, [x2, #KVM_VGIC_VCTRL]
+ kern_hyp_va x2
+ cbz x2, 1f // disabled
+
+ /* Clear GICH_HCR */
+ str wzr, [x2, #GICH_HCR]
+1: ret
+ENDPROC(__vgic_v2_disable)
+
/*
* Save the VGIC CPU state into memory
* x0: Register pointing to VCPU struct
* Do not corrupt x1!!!
*/
ENTRY(__save_vgic_v2_state)
-__save_vgic_v2_state:
/* Get VGIC VCTRL base into x2 */
ldr x2, [x0, #VCPU_KVM]
kern_hyp_va x2
@@ -75,7 +89,7 @@ CPU_BE( str w10, [x3, #VGIC_V2_CPU_ELRSR] )
str w11, [x3, #VGIC_V2_CPU_APR]
/* Clear GICH_HCR */
- str wzr, [x2, #GICH_HCR]
+ifnvhe _S_(str wzr, [x2, #GICH_HCR]), nop
/* Save list registers */
add x2, x2, #GICH_LR0
@@ -95,7 +109,6 @@ ENDPROC(__save_vgic_v2_state)
* x0: Register pointing to VCPU struct
*/
ENTRY(__restore_vgic_v2_state)
-__restore_vgic_v2_state:
/* Get VGIC VCTRL base into x2 */
ldr x2, [x0, #VCPU_KVM]
kern_hyp_va x2
diff --git a/arch/arm64/kvm/vgic-v3-switch.S b/arch/arm64/kvm/vgic-v3-switch.S
index 3c20730..b9b45e3 100644
--- a/arch/arm64/kvm/vgic-v3-switch.S
+++ b/arch/arm64/kvm/vgic-v3-switch.S
@@ -25,6 +25,8 @@
#include <asm/kvm_asm.h>
#include <asm/kvm_arm.h>
+#include "vhe-macros.h"
+
.text
.pushsection .hyp.text, "ax"
@@ -35,11 +37,21 @@
#define LR_OFFSET(n) (VGIC_V3_CPU_LR + (15 - n) * 8)
/*
+ * Disable the vcpu interface, preventing interrupts from
+ * being delivered.
+ */
+ENTRY(__vgic_v3_disable)
+ // Nuke the HCR register.
+ msr_s ICH_HCR_EL2, xzr
+ ret
+ENDPROC(__vgic_v3_disable)
+
+/*
* Save the VGIC CPU state into memory
* x0: Register pointing to VCPU struct
* Do not corrupt x1!!!
*/
-.macro save_vgic_v3_state
+ENTRY(__save_vgic_v3_state)
// Compute the address of struct vgic_cpu
add x3, x0, #VCPU_VGIC_CPU
@@ -58,7 +70,7 @@
str w7, [x3, #VGIC_V3_CPU_EISR]
str w8, [x3, #VGIC_V3_CPU_ELRSR]
- msr_s ICH_HCR_EL2, xzr
+ifnvhe _S_(msr_s ICH_HCR_EL2, xzr), nop
mrs_s x21, ICH_VTR_EL2
mvn w22, w21
@@ -137,15 +149,17 @@
orr x5, x5, #ICC_SRE_EL2_ENABLE
msr_s ICC_SRE_EL2, x5
isb
- mov x5, #1
+ // If using VHE, we don't care about EL1 and can early out.
+ifnvhe "mov x5, #1", ret
msr_s ICC_SRE_EL1, x5
-.endm
+ ret
+ENDPROC(__save_vgic_v3_state)
/*
* Restore the VGIC CPU state from memory
* x0: Register pointing to VCPU struct
*/
-.macro restore_vgic_v3_state
+ENTRY(__restore_vgic_v3_state)
// Compute the address of struct vgic_cpu
add x3, x0, #VCPU_VGIC_CPU
@@ -249,15 +263,6 @@
and x5, x5, #~ICC_SRE_EL2_ENABLE
msr_s ICC_SRE_EL2, x5
1:
-.endm
-
-ENTRY(__save_vgic_v3_state)
- save_vgic_v3_state
- ret
-ENDPROC(__save_vgic_v3_state)
-
-ENTRY(__restore_vgic_v3_state)
- restore_vgic_v3_state
ret
ENDPROC(__restore_vgic_v3_state)
--
2.1.4
--
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