[PATCH 06/17] KVM: arm64: Add {flush,sync}_hyp_timer_state() primitives
From: Fuad Tabba <fuad.tabba@linux.dev>
Date: 2026-08-31 16:34:42
Also in:
kvmarm, lkml
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
From: Marc Zyngier <maz@kernel.org> A protected guest's virtual timer is programmed from EL2's own copy of the state and read back there, so the host cannot change the guest's deadline. cntvoff_el2 is zeroed, so the guest's virtual time is the physical time. The flush also preserves the guest's CNTV and CNTP CVAL/CTL across the host's full-context copy into the hyp vCPU. Signed-off-by: Marc Zyngier <maz@kernel.org> Co-developed-by: Fuad Tabba <fuad.tabba@linux.dev> Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev> --- arch/arm64/kvm/hyp/nvhe/hyp-main.c | 39 ++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+)
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 14e847b122abf..d4b0f69ff130c 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c@@ -154,6 +154,33 @@ static void sync_hyp_vgic_state(struct pkvm_hyp_vcpu *hyp_vcpu) host_cpu_if->vgic_lr[i] = hyp_cpu_if->vgic_lr[i]; } +static void flush_hyp_timer_state(struct pkvm_hyp_vcpu *hyp_vcpu) +{ + if (!pkvm_hyp_vcpu_is_protected(hyp_vcpu)) + return; + + /* A hyp vcpu has no offset, and sees vtime == ptime. */ + write_sysreg(0, cntvoff_el2); + write_sysreg_el0(__vcpu_sys_reg(&hyp_vcpu->vcpu, CNTV_CVAL_EL0), + SYS_CNTV_CVAL); + isb(); + write_sysreg_el0(__vcpu_sys_reg(&hyp_vcpu->vcpu, CNTV_CTL_EL0), + SYS_CNTV_CTL); +} + +static void sync_hyp_timer_state(struct pkvm_hyp_vcpu *hyp_vcpu) +{ + if (!pkvm_hyp_vcpu_is_protected(hyp_vcpu)) + return; + + /* + * Preserve the vtimer state so that it is always correct, + * even if the host tries to make a mess. + */ + __vcpu_assign_sys_reg(&hyp_vcpu->vcpu, CNTV_CVAL_EL0, read_sysreg_el0(SYS_CNTV_CVAL)); + __vcpu_assign_sys_reg(&hyp_vcpu->vcpu, CNTV_CTL_EL0, read_sysreg_el0(SYS_CNTV_CTL)); +} + static void __copy_vcpu_state(const struct kvm_vcpu *from_vcpu, struct kvm_vcpu *to_vcpu) {
@@ -249,7 +276,17 @@ static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) hyp_vcpu->vcpu.arch.iflags = host_vcpu->arch.iflags; flush_debug_state(hyp_vcpu); } else { + u64 v_cval = hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTV_CVAL_EL0]; + u64 v_ctl = hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTV_CTL_EL0]; + u64 p_cval = hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTP_CVAL_EL0]; + u64 p_ctl = hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTP_CTL_EL0]; + hyp_vcpu->vcpu.arch.ctxt = host_vcpu->arch.ctxt; + + hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTV_CVAL_EL0] = v_cval; + hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTV_CTL_EL0] = v_ctl; + hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTP_CVAL_EL0] = p_cval; + hyp_vcpu->vcpu.arch.ctxt.sys_regs[CNTP_CTL_EL0] = p_ctl; } /* __hyp_running_vcpu must be NULL in a guest context. */
@@ -264,6 +301,7 @@ static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) hyp_vcpu->vcpu.arch.vsesr_el2 = host_vcpu->arch.vsesr_el2; flush_hyp_vgic_state(hyp_vcpu); + flush_hyp_timer_state(hyp_vcpu); hyp_vcpu->vcpu.arch.pid = host_vcpu->arch.pid;
@@ -313,6 +351,7 @@ static void sync_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu, u32 exit_reason) host_vcpu->arch.hcr_el2 |= hyp_vcpu->vcpu.arch.hcr_el2 & HCR_VSE; sync_hyp_vgic_state(hyp_vcpu); + sync_hyp_timer_state(hyp_vcpu); hyp_vcpu->exit_code = exit_reason; }
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2.39.5