[PATCH v6 19/21] KVM: arm64: Emulate physical counter offsetting on non-ECV systems
From: Oliver Upton <hidden>
Date: 2021-08-04 09:14:37
Also in:
kvmarm, linux-arm-kernel
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
Unfortunately, ECV hasn't yet arrived in any tangible hardware. At the same time, controlling the guest view of the physical counter-timer is useful. Support guest counter-timer offsetting on non-ECV systems by trapping guest accesses to the physical counter-timer. Emulate reads of the physical counter in the fast exit path. Signed-off-by: Oliver Upton <redacted> --- arch/arm64/include/asm/sysreg.h | 1 + arch/arm64/kvm/arch_timer.c | 53 +++++++++++++++---------- arch/arm64/kvm/hyp/include/hyp/switch.h | 29 ++++++++++++++ arch/arm64/kvm/hyp/nvhe/timer-sr.c | 11 ++++- 4 files changed, 70 insertions(+), 24 deletions(-)
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index c34672aa65b9..e49790ae5da4 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h@@ -505,6 +505,7 @@ #define SYS_AMEVCNTR0_MEM_STALL SYS_AMEVCNTR0_EL0(3) #define SYS_CNTFRQ_EL0 sys_reg(3, 3, 14, 0, 0) +#define SYS_CNTPCT_EL0 sys_reg(3, 3, 14, 0, 1) #define SYS_CNTP_TVAL_EL0 sys_reg(3, 3, 14, 2, 0) #define SYS_CNTP_CTL_EL0 sys_reg(3, 3, 14, 2, 1)
diff --git a/arch/arm64/kvm/arch_timer.c b/arch/arm64/kvm/arch_timer.c
index 9ead94aa867d..b7cb63acf2a0 100644
--- a/arch/arm64/kvm/arch_timer.c
+++ b/arch/arm64/kvm/arch_timer.c@@ -51,7 +51,7 @@ static void kvm_arm_timer_write(struct kvm_vcpu *vcpu, static u64 kvm_arm_timer_read(struct kvm_vcpu *vcpu, struct arch_timer_context *timer, enum kvm_arch_timer_regs treg); -static void kvm_timer_enable_traps_vhe(void); +static void kvm_timer_enable_traps_vhe(struct kvm_vcpu *vcpu); u32 timer_get_ctl(struct arch_timer_context *ctxt) {
@@ -175,6 +175,12 @@ static void timer_set_guest_offset(struct arch_timer_context *ctxt, u64 offset) } } +static bool ptimer_emulation_required(struct kvm_vcpu *vcpu) +{ + return timer_get_offset(vcpu_ptimer(vcpu)) && + !cpus_have_const_cap(ARM64_ECV); +} + u64 kvm_phys_timer_read(void) { return timecounter->cc->read(timecounter->cc);
@@ -184,8 +190,13 @@ static void get_timer_map(struct kvm_vcpu *vcpu, struct timer_map *map) { if (has_vhe()) { map->direct_vtimer = vcpu_vtimer(vcpu); - map->direct_ptimer = vcpu_ptimer(vcpu); - map->emul_ptimer = NULL; + if (!ptimer_emulation_required(vcpu)) { + map->direct_ptimer = vcpu_ptimer(vcpu); + map->emul_ptimer = NULL; + } else { + map->direct_ptimer = NULL; + map->emul_ptimer = vcpu_ptimer(vcpu); + } } else { map->direct_vtimer = vcpu_vtimer(vcpu); map->direct_ptimer = NULL;
@@ -671,7 +682,7 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu) timer_emulate(map.emul_ptimer); if (has_vhe()) - kvm_timer_enable_traps_vhe(); + kvm_timer_enable_traps_vhe(vcpu); } bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu)
@@ -1392,22 +1403,29 @@ int kvm_timer_enable(struct kvm_vcpu *vcpu) * The host kernel runs at EL2 with HCR_EL2.TGE == 1, * and this makes those bits have no effect for the host kernel execution. */ -static void kvm_timer_enable_traps_vhe(void) +static void kvm_timer_enable_traps_vhe(struct kvm_vcpu *vcpu) { /* When HCR_EL2.E2H ==1, EL1PCEN and EL1PCTEN are shifted by 10 */ u32 cnthctl_shift = 10; - u64 val; + u64 val, mask; + + mask = CNTHCTL_EL1PCEN << cnthctl_shift; + mask |= CNTHCTL_EL1PCTEN << cnthctl_shift; - /* - * VHE systems allow the guest direct access to the EL1 physical - * timer/counter. - */ val = read_sysreg(cnthctl_el2); - val |= (CNTHCTL_EL1PCEN << cnthctl_shift); - val |= (CNTHCTL_EL1PCTEN << cnthctl_shift); if (cpus_have_const_cap(ARM64_ECV)) val |= CNTHCTL_ECV; + + /* + * VHE systems allow the guest direct access to the EL1 physical + * timer/counter if offsetting isn't requested on a non-ECV system. + */ + if (ptimer_emulation_required(vcpu)) + val &= ~mask; + else + val |= mask; + write_sysreg(val, cnthctl_el2); }
@@ -1462,9 +1480,6 @@ static int kvm_arm_timer_set_attr_offset(struct kvm_vcpu *vcpu, u64 __user *uaddr = (u64 __user *)(long)attr->addr; u64 offset; - if (!cpus_have_const_cap(ARM64_ECV)) - return -ENXIO; - if (get_user(offset, uaddr)) return -EFAULT;
@@ -1513,9 +1528,6 @@ static int kvm_arm_timer_get_attr_offset(struct kvm_vcpu *vcpu, u64 __user *uaddr = (u64 __user *)(long)attr->addr; u64 offset; - if (!cpus_have_const_cap(ARM64_ECV)) - return -ENXIO; - offset = timer_get_offset(vcpu_ptimer(vcpu)); return put_user(offset, uaddr); }
@@ -1539,11 +1551,8 @@ int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) switch (attr->attr) { case KVM_ARM_VCPU_TIMER_IRQ_VTIMER: case KVM_ARM_VCPU_TIMER_IRQ_PTIMER: - return 0; case KVM_ARM_VCPU_TIMER_OFFSET: - if (cpus_have_const_cap(ARM64_ECV)) - return 0; - break; + return 0; } return -ENXIO;
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index e4a2f295a394..abd3813a709e 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h@@ -15,6 +15,7 @@ #include <linux/jump_label.h> #include <uapi/linux/psci.h> +#include <kvm/arm_arch_timer.h> #include <kvm/arm_psci.h> #include <asm/barrier.h>
@@ -405,6 +406,31 @@ static inline bool __hyp_handle_ptrauth(struct kvm_vcpu *vcpu) return true; } +static inline u64 __timer_read_cntpct(struct kvm_vcpu *vcpu) +{ + return __arch_counter_get_cntpct() - vcpu_ptimer(vcpu)->host_offset; +} + +static inline bool __hyp_handle_counter(struct kvm_vcpu *vcpu) +{ + u32 sysreg; + int rt; + u64 rv; + + if (kvm_vcpu_trap_get_class(vcpu) != ESR_ELx_EC_SYS64) + return false; + + sysreg = esr_sys64_to_sysreg(kvm_vcpu_get_esr(vcpu)); + if (sysreg != SYS_CNTPCT_EL0) + return false; + + rt = kvm_vcpu_sys_get_rt(vcpu); + rv = __timer_read_cntpct(vcpu); + vcpu_set_reg(vcpu, rt, rv); + __kvm_skip_instr(vcpu); + return true; +} + /* * Return true when we were able to fixup the guest exit and should return to * the guest, false when we should restore the host state and return to the
@@ -439,6 +465,9 @@ static inline bool fixup_guest_exit(struct kvm_vcpu *vcpu, u64 *exit_code) if (*exit_code != ARM_EXCEPTION_TRAP) goto exit; + if (__hyp_handle_counter(vcpu)) + goto guest; + if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM) && kvm_vcpu_trap_get_class(vcpu) == ESR_ELx_EC_SYS64 && handle_tx2_tvm(vcpu))
diff --git a/arch/arm64/kvm/hyp/nvhe/timer-sr.c b/arch/arm64/kvm/hyp/nvhe/timer-sr.c
index 5b8b4cd02506..67236c2e0ba7 100644
--- a/arch/arm64/kvm/hyp/nvhe/timer-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/timer-sr.c@@ -44,10 +44,17 @@ void __timer_enable_traps(struct kvm_vcpu *vcpu) /* * Disallow physical timer access for the guest - * Physical counter access is allowed */ val = read_sysreg(cnthctl_el2); val &= ~CNTHCTL_EL1PCEN; - val |= CNTHCTL_EL1PCTEN; + + /* + * Disallow physical counter access for the guest if offsetting is + * requested on a non-ECV system. + */ + if (vcpu_ptimer(vcpu)->host_offset && !cpus_have_const_cap(ARM64_ECV)) + val &= ~CNTHCTL_EL1PCTEN; + else + val |= CNTHCTL_EL1PCTEN; write_sysreg(val, cnthctl_el2); }
--
2.32.0.605.g8dce9f2422-goog