KVM: arm/arm64: Move timer save/restore out of the hyp code

As we are about to be lazy with saving and restoring the timer
registers, we prepare by moving all possible timer configuration logic
out of the hyp code.  All virtual timer registers can be programmed from
EL1 and since the arch timer is always a level triggered interrupt we
can safely do this with interrupts disabled in the host kernel on the
way to the guest without taking vtimer interrupts in the host kernel
(yet).

The downside is that the cntvoff register can only be programmed from
hyp mode, so we jump into hyp mode and back to program it.  This is also
safe, because the host kernel doesn't use the virtual timer in the KVM
code.  It may add a little performance performance penalty, but only
until following commits where we move this operation to vcpu load/put.

Signed-off-by: Christoffer Dall <cdall@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/arch/arm/include/asm/kvm_asm.h b/arch/arm/include/asm/kvm_asm.h
index 14d68a4d826f6388af790b91bc3c2ae7fa80de13..36dd2962a42db2868badb568e38118884321eddb 100644 (file)
--- a/arch/arm/include/asm/kvm_asm.h
+++ b/arch/arm/include/asm/kvm_asm.h
@@ -68,6 +68,8 @@ extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
 extern void __kvm_tlb_flush_vmid(struct kvm *kvm);
 extern void __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu);
 
+extern void __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high);
+
 extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
 
 extern void __init_stage2_translation(void);

diff --git a/arch/arm/include/asm/kvm_hyp.h b/arch/arm/include/asm/kvm_hyp.h
index 14b5903f022461a2f090ad16ff7880e13cea04d3..ab20ffa8b9e7658bc73779b7b6ae711f140d2105 100644 (file)
--- a/arch/arm/include/asm/kvm_hyp.h
+++ b/arch/arm/include/asm/kvm_hyp.h
@@ -98,8 +98,8 @@
 #define cntvoff_el2                    CNTVOFF
 #define cnthctl_el2                    CNTHCTL
 
-void __timer_save_state(struct kvm_vcpu *vcpu);
-void __timer_restore_state(struct kvm_vcpu *vcpu);
+void __timer_enable_traps(struct kvm_vcpu *vcpu);
+void __timer_disable_traps(struct kvm_vcpu *vcpu);
 
 void __vgic_v2_save_state(struct kvm_vcpu *vcpu);
 void __vgic_v2_restore_state(struct kvm_vcpu *vcpu);

diff --git a/arch/arm/kvm/hyp/switch.c b/arch/arm/kvm/hyp/switch.c
index ebd2dd46adf7f991d7131eb55873a5e916010a8d..330c9ce34ba5f68ceb7907d9a41415d598fd0b0a 100644 (file)
--- a/arch/arm/kvm/hyp/switch.c
+++ b/arch/arm/kvm/hyp/switch.c
@@ -174,7 +174,7 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
        __activate_vm(vcpu);
 
        __vgic_restore_state(vcpu);
-       __timer_restore_state(vcpu);
+       __timer_enable_traps(vcpu);
 
        __sysreg_restore_state(guest_ctxt);
        __banked_restore_state(guest_ctxt);
@@ -191,7 +191,8 @@ again:
 
        __banked_save_state(guest_ctxt);
        __sysreg_save_state(guest_ctxt);
-       __timer_save_state(vcpu);
+       __timer_disable_traps(vcpu);
+
        __vgic_save_state(vcpu);
 
        __deactivate_traps(vcpu);
@@ -237,7 +238,7 @@ void __hyp_text __noreturn __hyp_panic(int cause)
 
                vcpu = (struct kvm_vcpu *)read_sysreg(HTPIDR);
                host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
-               __timer_save_state(vcpu);
+               __timer_disable_traps(vcpu);
                __deactivate_traps(vcpu);
                __deactivate_vm(vcpu);
                __banked_restore_state(host_ctxt);

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 26a64d0f9ab919445de352588bf9a6df4f273e5c..ab4d0a926043a51b2eae6354a8cc12c5a8b3b303 100644 (file)
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -55,6 +55,8 @@ extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
 extern void __kvm_tlb_flush_vmid(struct kvm *kvm);
 extern void __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu);
 
+extern void __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high);
+
 extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
 
 extern u64 __vgic_v3_get_ich_vtr_el2(void);

diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 4572a9b560fa3d73a7db4a850215bcbc9049c8f1..08d3bb66c8b75be2a39a1fa35946126db07cf479 100644 (file)
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -129,8 +129,8 @@ void __vgic_v3_save_state(struct kvm_vcpu *vcpu);
 void __vgic_v3_restore_state(struct kvm_vcpu *vcpu);
 int __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu);
 
-void __timer_save_state(struct kvm_vcpu *vcpu);
-void __timer_restore_state(struct kvm_vcpu *vcpu);
+void __timer_enable_traps(struct kvm_vcpu *vcpu);
+void __timer_disable_traps(struct kvm_vcpu *vcpu);
 
 void __sysreg_save_host_state(struct kvm_cpu_context *ctxt);
 void __sysreg_restore_host_state(struct kvm_cpu_context *ctxt);

diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 945e79c641c4a2b69dc0a1b97c5b68c5f99d6bc0..4994f4bdaca5d49f7bc31f6a229b46ce7f0257d6 100644 (file)
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -298,7 +298,7 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
        __activate_vm(vcpu);
 
        __vgic_restore_state(vcpu);
-       __timer_restore_state(vcpu);
+       __timer_enable_traps(vcpu);
 
        /*
         * We must restore the 32-bit state before the sysregs, thanks
@@ -368,7 +368,7 @@ again:
 
        __sysreg_save_guest_state(guest_ctxt);
        __sysreg32_save_state(vcpu);
-       __timer_save_state(vcpu);
+       __timer_disable_traps(vcpu);
        __vgic_save_state(vcpu);
 
        __deactivate_traps(vcpu);
@@ -436,7 +436,7 @@ void __hyp_text __noreturn __hyp_panic(void)
 
                vcpu = (struct kvm_vcpu *)read_sysreg(tpidr_el2);
                host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
-               __timer_save_state(vcpu);
+               __timer_disable_traps(vcpu);
                __deactivate_traps(vcpu);
                __deactivate_vm(vcpu);
                __sysreg_restore_host_state(host_ctxt);

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 4ad853737c3434e06e16616509c2c97e6bae4935..93c8973a71f47f28b9252bc633b8f79eb5151a54 100644 (file)
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -271,6 +271,20 @@ static void phys_timer_emulate(struct kvm_vcpu *vcpu,
        soft_timer_start(&timer->phys_timer, kvm_timer_compute_delta(timer_ctx));
 }
 
+static void timer_save_state(struct kvm_vcpu *vcpu)
+{
+       struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+       struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
+
+       if (timer->enabled) {
+               vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
+               vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
+       }
+
+       /* Disable the virtual timer */
+       write_sysreg_el0(0, cntv_ctl);
+}
+
 /*
  * Schedule the background timer before calling kvm_vcpu_block, so that this
  * thread is removed from its waitqueue and made runnable when there's a timer
@@ -304,6 +318,18 @@ void kvm_timer_schedule(struct kvm_vcpu *vcpu)
        soft_timer_start(&timer->bg_timer, kvm_timer_earliest_exp(vcpu));
 }
 
+static void timer_restore_state(struct kvm_vcpu *vcpu)
+{
+       struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+       struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
+
+       if (timer->enabled) {
+               write_sysreg_el0(vtimer->cnt_cval, cntv_cval);
+               isb();
+               write_sysreg_el0(vtimer->cnt_ctl, cntv_ctl);
+       }
+}
+
 void kvm_timer_unschedule(struct kvm_vcpu *vcpu)
 {
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
@@ -311,6 +337,21 @@ void kvm_timer_unschedule(struct kvm_vcpu *vcpu)
        soft_timer_cancel(&timer->bg_timer, &timer->expired);
 }
 
+static void set_cntvoff(u64 cntvoff)
+{
+       u32 low = lower_32_bits(cntvoff);
+       u32 high = upper_32_bits(cntvoff);
+
+       /*
+        * Since kvm_call_hyp doesn't fully support the ARM PCS especially on
+        * 32-bit systems, but rather passes register by register shifted one
+        * place (we put the function address in r0/x0), we cannot simply pass
+        * a 64-bit value as an argument, but have to split the value in two
+        * 32-bit halves.
+        */
+       kvm_call_hyp(__kvm_timer_set_cntvoff, low, high);
+}
+
 static void kvm_timer_flush_hwstate_vgic(struct kvm_vcpu *vcpu)
 {
        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
@@ -414,6 +455,7 @@ static void kvm_timer_flush_hwstate_user(struct kvm_vcpu *vcpu)
 void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
 {
        struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+       struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
 
        if (unlikely(!timer->enabled))
                return;
@@ -427,6 +469,9 @@ void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
                kvm_timer_flush_hwstate_user(vcpu);
        else
                kvm_timer_flush_hwstate_vgic(vcpu);
+
+       set_cntvoff(vtimer->cntvoff);
+       timer_restore_state(vcpu);
 }
 
 /**
@@ -446,6 +491,9 @@ void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
         */
        soft_timer_cancel(&timer->phys_timer, NULL);
 
+       timer_save_state(vcpu);
+       set_cntvoff(0);
+
        /*
         * The guest could have modified the timer registers or the timer
         * could have expired, update the timer state.

diff --git a/virt/kvm/arm/hyp/timer-sr.c b/virt/kvm/arm/hyp/timer-sr.c
index 4734915ab71f78e71c598ec5bbb7b7b2eb73a084..f39861639f08f81a305fff841f0f08dcf0878686 100644 (file)
--- a/virt/kvm/arm/hyp/timer-sr.c
+++ b/virt/kvm/arm/hyp/timer-sr.c
@@ -21,58 +21,48 @@
 
 #include <asm/kvm_hyp.h>
 
-/* vcpu is already in the HYP VA space */
-void __hyp_text __timer_save_state(struct kvm_vcpu *vcpu)
+void __hyp_text __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high)
+{
+       u64 cntvoff = (u64)cntvoff_high << 32 | cntvoff_low;
+       write_sysreg(cntvoff, cntvoff_el2);
+}
+
+void __hyp_text enable_el1_phys_timer_access(void)
 {
-       struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
-       struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
        u64 val;
 
-       if (timer->enabled) {
-               vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
-               vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
-       }
+       /* Allow physical timer/counter access for the host */
+       val = read_sysreg(cnthctl_el2);
+       val |= CNTHCTL_EL1PCTEN | CNTHCTL_EL1PCEN;
+       write_sysreg(val, cnthctl_el2);
+}
 
-       /* Disable the virtual timer */
-       write_sysreg_el0(0, cntv_ctl);
+void __hyp_text disable_el1_phys_timer_access(void)
+{
+       u64 val;
 
+       /*
+        * Disallow physical timer access for the guest
+        * Physical counter access is allowed
+        */
+       val = read_sysreg(cnthctl_el2);
+       val &= ~CNTHCTL_EL1PCEN;
+       val |= CNTHCTL_EL1PCTEN;
+       write_sysreg(val, cnthctl_el2);
+}
+
+void __hyp_text __timer_disable_traps(struct kvm_vcpu *vcpu)
+{
        /*
         * We don't need to do this for VHE since the host kernel runs in EL2
         * with HCR_EL2.TGE ==1, which makes those bits have no impact.
         */
-       if (!has_vhe()) {
-               /* Allow physical timer/counter access for the host */
-               val = read_sysreg(cnthctl_el2);
-               val |= CNTHCTL_EL1PCTEN | CNTHCTL_EL1PCEN;
-               write_sysreg(val, cnthctl_el2);
-       }
-
-       /* Clear cntvoff for the host */
-       write_sysreg(0, cntvoff_el2);
+       if (!has_vhe())
+               enable_el1_phys_timer_access();
 }
 
-void __hyp_text __timer_restore_state(struct kvm_vcpu *vcpu)
+void __hyp_text __timer_enable_traps(struct kvm_vcpu *vcpu)
 {
-       struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
-       struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
-       u64 val;
-
-       /* Those bits are already configured at boot on VHE-system */
-       if (!has_vhe()) {
-               /*
-                * Disallow physical timer access for the guest
-                * Physical counter access is allowed
-                */
-               val = read_sysreg(cnthctl_el2);
-               val &= ~CNTHCTL_EL1PCEN;
-               val |= CNTHCTL_EL1PCTEN;
-               write_sysreg(val, cnthctl_el2);
-       }
-
-       if (timer->enabled) {
-               write_sysreg(vtimer->cntvoff, cntvoff_el2);
-               write_sysreg_el0(vtimer->cnt_cval, cntv_cval);
-               isb();
-               write_sysreg_el0(vtimer->cnt_ctl, cntv_ctl);
-       }
+       if (!has_vhe())
+               disable_el1_phys_timer_access();
 }