From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4412C3D966A for ; Fri, 12 Jun 2026 06:59:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781247584; cv=none; b=Sh4tREdURepvYpNU0/Hi+DHZehG02vLbpB01S1X9YeovVg2j+tKVNQPgP6doLNbfZkyuyxIp1UEkA8HB72o21KhlfvSphhR9QIuBU3i1FcVUczjTSxMLsRVHPY1bgHzGvW3PXVnzIDOGmovE/3YoJSer+jRT98cOa4wAKLHnMO4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781247584; c=relaxed/simple; bh=bye8nd/QNV44tiU0PhzJB9r9DA6Q0Ug13E8Lsno86/8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=F2jYuybC1Cs099FJtRRJ+W1EERRa5i5GbLAsh3juMULAX4KuzfZp60dWOK1r2sItYtmBgCOx57ce5GEK9IaI7K9ksqXYqcHDxX7hI8RzzCGlH1y0/KXcQUhDJVxK+w89PXkDgZu6jN7zaLsPoSJl5koUjaZbc1GAckGYyrVosNY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--tabba.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=MaiQTIXy; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--tabba.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="MaiQTIXy" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-490ab3f6e55so3410595e9.0 for ; Thu, 11 Jun 2026 23:59:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1781247579; x=1781852379; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Q37dujmcv40LywWyg6EwCNTlgdLzHM44RSz9WVrB3kg=; b=MaiQTIXyte1E+kvJbGEbwATcYb3kQjjSPJ0DCqGrxQr/E5TLQ2ZF2CnWU9xqRwvGe7 2Vz1XuZ9B62BjjvkcYU4FiclLJ9QebqbWcRGPoZVsiBLh+Nsyo7rnnUoqiRccCk1gNZI giq7/IctQZAdKcUA8undmxwoaT4UK9x2g1d/0U2oMp6jMKsmPVUmgM/hS3/09xNWfsUX 5jbP6+qXnAL1Ly4Y/poX2b01G4ICjTfNZCoJ/0AidRkl5X9DgADHNc79pQnsO9eH3prc d0AJKQwaAR5LdzJbDEksQTzSQCQSFMklS6p3AlCkKd7SBVp0rKwJHSYK70L0MOLP28Kj Yoqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781247579; x=1781852379; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Q37dujmcv40LywWyg6EwCNTlgdLzHM44RSz9WVrB3kg=; b=j+6gqbPG3/Izs6I94q9hctVmMtvPElV0Waq6ZaxABQJLKrU6R9U5N5S+P5y3dYeNv6 ZEPvF4TT53cYZbZdgiZrSZ0vvMg9VLpi25zlRZbsGa/wt0Wy3+0cNmmOEkSfUVx3UfoS 9+VdNwtd/6peC8th5TmEz2m0t9inuzwlAIahqwgmccH+9tCr31SFiXhMQU+ws9jwRzJf +TIeWV13h+1LroWMTeUq2qBUgapIWitcH3QvmV32X/r3BzvFdZ+N1zMl0ySN5ieKiSrn ui1lJDRVKMHdzV/B17llUA7lGr9qEF8GW/1O+RKlK1Caz8OJZiSNT5Y3OyPazec36+JD F+Hg== X-Forwarded-Encrypted: i=1; AFNElJ+nztZAPSrncOzr01L8/82wHAvw30NCj5eq5cuOsKu561d03rb9FqZ5Rkx69cwbSP1lWcWrbbU=@lists.linux.dev X-Gm-Message-State: AOJu0Yy2um40AN2Lagmf6Vmk+UwZM1SNcRECoj3CIXQ/C26ZpAhJfRY4 9xCedBovOXGXutYT3sTUoFYXWR6Coh64p/CG/WkwuqbQyr8gLmFqMa4UmbqSEbmIrIzh3dY5slS Adg== X-Received: from wmom24.prod.google.com ([2002:a05:600c:4618:b0:490:addd:1d76]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:2d84:b0:490:c2a3:1781 with SMTP id 5b1f17b1804b1-490ec50a93dmr8358995e9.34.1781247578382; Thu, 11 Jun 2026 23:59:38 -0700 (PDT) Date: Fri, 12 Jun 2026 07:59:25 +0100 In-Reply-To: <20260612065925.755562-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260612065925.755562-1-tabba@google.com> X-Mailer: git-send-email 2.54.0.1136.gdb2ca164c4-goog Message-ID: <20260612065925.755562-12-tabba@google.com> Subject: [PATCH v1 11/11] KVM: arm64: Implement lazy vCPU state sync for non-protected guests From: tabba@google.com To: Marc Zyngier , Oliver Upton Cc: Fuad Tabba , Will Deacon , Catalin Marinas , Quentin Perret , Vincent Donnefort , Sebastian Ene , Per Larsen , Suzuki K Poulose , Zenghui Yu , Joey Gouly , Steffen Eiden , Mark Rutland , Jonathan Cameron , Hyunwoo Kim , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" pKVM copies a non-protected guest's register context between the host and the hypervisor on every world switch, even when the host never inspects it. Defer the copy: on entry, flush the host context into the hyp vCPU only when the host marked it dirty (PKVM_HOST_STATE_DIRTY); on exit, leave it in the hyp vCPU and copy it back only when the host needs it, via a __pkvm_vcpu_sync_state hypercall on trap handling or at vcpu put. A protected guest's context is copied as before, since lazy sync only helps where the host is trusted to see the guest's registers. The PC is the exception: it is copied back on every exit so the kvm_exit tracepoint reports the guest's real exit PC rather than the value left by the previous sync. Signed-off-by: Fuad Tabba --- arch/arm64/include/asm/kvm_asm.h | 1 + arch/arm64/include/asm/kvm_host.h | 2 + arch/arm64/kvm/arm.c | 7 +++ arch/arm64/kvm/handle_exit.c | 22 ++++++++ arch/arm64/kvm/hyp/nvhe/hyp-main.c | 88 ++++++++++++++++++++++++++++-- 5 files changed, 115 insertions(+), 5 deletions(-) diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h index 043495f7fc78..6e1135b3ded4 100644 --- a/arch/arm64/include/asm/kvm_asm.h +++ b/arch/arm64/include/asm/kvm_asm.h @@ -113,6 +113,7 @@ enum __kvm_host_smccc_func { __KVM_HOST_SMCCC_FUNC___pkvm_finalize_teardown_vm, __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_load, __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_put, + __KVM_HOST_SMCCC_FUNC___pkvm_vcpu_sync_state, __KVM_HOST_SMCCC_FUNC___pkvm_tlb_flush_vmid, MARKER(__KVM_HOST_SMCCC_FUNC_MAX) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index a49042bfa801..1ef660774adc 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1113,6 +1113,8 @@ struct kvm_vcpu_arch { /* SError pending for nested guest */ #define NESTED_SERROR_PENDING __vcpu_single_flag(sflags, BIT(8)) +/* pKVM host vcpu state is dirty, needs resync (nVHE-only) */ +#define PKVM_HOST_STATE_DIRTY __vcpu_single_flag(iflags, BIT(4)) /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */ #define vcpu_sve_pffr(vcpu) (kern_hyp_va((vcpu)->arch.sve_state) + \ diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index c9f36932c980..a5c54e37778b 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -734,6 +734,10 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) if (is_protected_kvm_enabled()) { kvm_call_hyp(__vgic_v3_save_aprs, &vcpu->arch.vgic_cpu.vgic_v3); kvm_call_hyp_nvhe(__pkvm_vcpu_put); + + /* __pkvm_vcpu_put implies a sync of the state */ + if (!kvm_vm_is_protected(vcpu->kvm)) + vcpu_set_flag(vcpu, PKVM_HOST_STATE_DIRTY); } kvm_vcpu_put_debug(vcpu); @@ -961,6 +965,9 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu) return ret; if (is_protected_kvm_enabled()) { + /* Start with the vcpu in a dirty state */ + if (!kvm_vm_is_protected(vcpu->kvm)) + vcpu_set_flag(vcpu, PKVM_HOST_STATE_DIRTY); ret = pkvm_create_hyp_vm(kvm); if (ret) return ret; diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c index 54aedf93c78b..dccc3786548b 100644 --- a/arch/arm64/kvm/handle_exit.c +++ b/arch/arm64/kvm/handle_exit.c @@ -422,6 +422,21 @@ static int handle_trap_exceptions(struct kvm_vcpu *vcpu) { int handled; + /* + * If we run a non-protected VM when protection is enabled + * system-wide, resync the state from the hypervisor and mark + * it as dirty on the host side if it wasn't dirty already + * (which could happen if preemption has taken place). + */ + if (is_protected_kvm_enabled() && !kvm_vm_is_protected(vcpu->kvm)) { + preempt_disable(); + if (!(vcpu_get_flag(vcpu, PKVM_HOST_STATE_DIRTY))) { + kvm_call_hyp_nvhe(__pkvm_vcpu_sync_state); + vcpu_set_flag(vcpu, PKVM_HOST_STATE_DIRTY); + } + preempt_enable(); + } + /* * See ARM ARM B1.14.1: "Hyp traps on instructions * that fail their condition code check" @@ -489,6 +504,13 @@ int handle_exit(struct kvm_vcpu *vcpu, int exception_index) /* For exit types that need handling before we can be preempted */ void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index) { + /* + * We just exited, so the state is clean from a hypervisor + * perspective. + */ + if (is_protected_kvm_enabled()) + vcpu_clear_flag(vcpu, PKVM_HOST_STATE_DIRTY); + if (ARM_SERROR_PENDING(exception_index)) { if (this_cpu_has_cap(ARM64_HAS_RAS_EXTN)) { u64 disr = kvm_vcpu_get_disr(vcpu); diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c index 23e644c24a03..02383b372258 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c @@ -139,6 +139,49 @@ 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 __copy_vcpu_state(const struct kvm_vcpu *from_vcpu, + struct kvm_vcpu *to_vcpu) +{ + int i; + + to_vcpu->arch.ctxt.regs = from_vcpu->arch.ctxt.regs; + to_vcpu->arch.ctxt.spsr_abt = from_vcpu->arch.ctxt.spsr_abt; + to_vcpu->arch.ctxt.spsr_und = from_vcpu->arch.ctxt.spsr_und; + to_vcpu->arch.ctxt.spsr_irq = from_vcpu->arch.ctxt.spsr_irq; + to_vcpu->arch.ctxt.spsr_fiq = from_vcpu->arch.ctxt.spsr_fiq; + to_vcpu->arch.ctxt.fp_regs = from_vcpu->arch.ctxt.fp_regs; + + /* + * Copy the sysregs, but don't mess with the timer state which + * is directly handled by EL1 and is expected to be preserved. + * enum vcpu_sysreg is sparse: VNCR-mapped registers take values + * derived from their VNCR page offset, so the timer registers do + * not form a contiguous numeric range and must be skipped by name. + */ + for (i = 1; i < NR_SYS_REGS; i++) { + switch (i) { + case CNTVOFF_EL2: + case CNTV_CVAL_EL0: + case CNTV_CTL_EL0: + case CNTP_CVAL_EL0: + case CNTP_CTL_EL0: + continue; + } + to_vcpu->arch.ctxt.sys_regs[i] = from_vcpu->arch.ctxt.sys_regs[i]; + } +} + +static void __sync_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) +{ + __copy_vcpu_state(&hyp_vcpu->vcpu, hyp_vcpu->host_vcpu); +} + +static void __flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) +{ + __copy_vcpu_state(hyp_vcpu->host_vcpu, &hyp_vcpu->vcpu); +} + static void flush_debug_state(struct pkvm_hyp_vcpu *hyp_vcpu) { struct kvm_vcpu *host_vcpu = hyp_vcpu->host_vcpu; @@ -168,7 +211,17 @@ static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) fpsimd_sve_flush(); flush_debug_state(hyp_vcpu); - hyp_vcpu->vcpu.arch.ctxt = host_vcpu->arch.ctxt; + /* + * If we deal with a non-protected guest and the state is potentially + * dirty (from a host perspective), copy the state back into the hyp + * vcpu. + */ + if (!pkvm_hyp_vcpu_is_protected(hyp_vcpu)) { + if (vcpu_get_flag(host_vcpu, PKVM_HOST_STATE_DIRTY)) + __flush_hyp_vcpu(hyp_vcpu); + } else { + hyp_vcpu->vcpu.arch.ctxt = host_vcpu->arch.ctxt; + } hyp_vcpu->vcpu.arch.mdcr_el2 = host_vcpu->arch.mdcr_el2; hyp_vcpu->vcpu.arch.hcr_el2 &= ~(HCR_TWI | HCR_TWE); @@ -191,9 +244,11 @@ static void sync_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu) fpsimd_sve_sync(&hyp_vcpu->vcpu); sync_debug_state(hyp_vcpu); - host_vcpu->arch.ctxt = hyp_vcpu->vcpu.arch.ctxt; - - host_vcpu->arch.hcr_el2 = hyp_vcpu->vcpu.arch.hcr_el2; + if (pkvm_hyp_vcpu_is_protected(hyp_vcpu)) + host_vcpu->arch.ctxt = hyp_vcpu->vcpu.arch.ctxt; + else + /* Keep the PC current for the kvm_exit tracepoint (lazy ctxt sync). */ + host_vcpu->arch.ctxt.regs.pc = hyp_vcpu->vcpu.arch.ctxt.regs.pc; host_vcpu->arch.fault = hyp_vcpu->vcpu.arch.fault; @@ -227,8 +282,30 @@ static void handle___pkvm_vcpu_put(struct kvm_cpu_context *host_ctxt) { struct pkvm_hyp_vcpu *hyp_vcpu = pkvm_get_loaded_hyp_vcpu(); - if (hyp_vcpu) + if (hyp_vcpu) { + struct kvm_vcpu *host_vcpu = hyp_vcpu->host_vcpu; + + if (!pkvm_hyp_vcpu_is_protected(hyp_vcpu) && + !vcpu_get_flag(host_vcpu, PKVM_HOST_STATE_DIRTY)) { + __sync_hyp_vcpu(hyp_vcpu); + } + pkvm_put_hyp_vcpu(hyp_vcpu); + } +} + +static void handle___pkvm_vcpu_sync_state(struct kvm_cpu_context *host_ctxt) +{ + struct pkvm_hyp_vcpu *hyp_vcpu; + + if (!is_protected_kvm_enabled()) + return; + + hyp_vcpu = pkvm_get_loaded_hyp_vcpu(); + if (!hyp_vcpu || pkvm_hyp_vcpu_is_protected(hyp_vcpu)) + return; + + __sync_hyp_vcpu(hyp_vcpu); } static struct kvm_vcpu *__get_host_hyp_vcpus(struct kvm_vcpu *arg, @@ -859,6 +936,7 @@ static const hcall_t host_hcall[] = { HANDLE_FUNC(__pkvm_finalize_teardown_vm), HANDLE_FUNC(__pkvm_vcpu_load), HANDLE_FUNC(__pkvm_vcpu_put), + HANDLE_FUNC(__pkvm_vcpu_sync_state), HANDLE_FUNC(__pkvm_tlb_flush_vmid), }; -- 2.54.0.1136.gdb2ca164c4-goog