From patchwork Tue Jun 9 02:12:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Kardashevskiy X-Patchwork-Id: 1305538 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 49gtwm5lJqz9sRW for ; Tue, 9 Jun 2020 12:14:32 +1000 (AEST) Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.ru Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 49gtwm3SGrzDqSt for ; Tue, 9 Jun 2020 12:14:32 +1000 (AEST) X-Original-To: linuxppc-dev@lists.ozlabs.org Delivered-To: linuxppc-dev@lists.ozlabs.org Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.ru (client-ip=107.174.27.60; helo=ozlabs.ru; envelope-from=aik@ozlabs.ru; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ozlabs.ru Received: from ozlabs.ru (unknown [107.174.27.60]) by lists.ozlabs.org (Postfix) with ESMTP id 49gtvF6ZYbzDqD2 for ; Tue, 9 Jun 2020 12:13:11 +1000 (AEST) Received: from fstn1-p1.ozlabs.ibm.com (localhost [IPv6:::1]) by ozlabs.ru (Postfix) with ESMTP id 35E39AE8000F; Mon, 8 Jun 2020 22:10:16 -0400 (EDT) From: Alexey Kardashevskiy To: linuxppc-dev@lists.ozlabs.org Subject: [PATCH kernel] KVM: PPC: Protect kvm_vcpu_read_guest with srcu locks Date: Tue, 9 Jun 2020 12:12:29 +1000 Message-Id: <20200609021230.103494-1-aik@ozlabs.ru> X-Mailer: git-send-email 2.17.1 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexey Kardashevskiy , kvm-ppc@vger.kernel.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" The kvm_vcpu_read_guest/kvm_vcpu_write_guest used for nested guests eventually call srcu_dereference_check to dereference a memslot and lockdep produces a warning as neither kvm->slots_lock nor kvm->srcu lock is held and kvm->users_count is above zero (>100 in fact). This wraps mentioned VCPU read/write helpers in srcu read lock/unlock as it is done in other places. This uses vcpu->srcu_idx when possible. These helpers are only used for nested KVM so this may explain why we did not see these before. Here is an example of a warning: ============================= WARNING: suspicious RCU usage 5.7.0-rc3-le_dma-bypass.3.2_a+fstn1 #897 Not tainted ----------------------------- include/linux/kvm_host.h:633 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by qemu-system-ppc/2752: #0: c000200359016be0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x144/0xd80 [kvm] stack backtrace: CPU: 80 PID: 2752 Comm: qemu-system-ppc Not tainted 5.7.0-rc3-le_dma-bypass.3.2_a+fstn1 #897 Call Trace: [c0002003591ab240] [c000000000b23ab4] dump_stack+0x190/0x25c (unreliable) [c0002003591ab2b0] [c00000000023f954] lockdep_rcu_suspicious+0x140/0x164 [c0002003591ab330] [c008000004a445f8] kvm_vcpu_gfn_to_memslot+0x4c0/0x510 [kvm] [c0002003591ab3a0] [c008000004a44c18] kvm_vcpu_read_guest+0xa0/0x180 [kvm] [c0002003591ab410] [c008000004ff9bd8] kvmhv_enter_nested_guest+0x90/0xb80 [kvm_hv] [c0002003591ab980] [c008000004fe07bc] kvmppc_pseries_do_hcall+0x7b4/0x1c30 [kvm_hv] [c0002003591aba10] [c008000004fe5d30] kvmppc_vcpu_run_hv+0x10a8/0x1a30 [kvm_hv] [c0002003591abae0] [c008000004a5d954] kvmppc_vcpu_run+0x4c/0x70 [kvm] [c0002003591abb10] [c008000004a56e54] kvm_arch_vcpu_ioctl_run+0x56c/0x7c0 [kvm] [c0002003591abba0] [c008000004a3ddc4] kvm_vcpu_ioctl+0x4ac/0xd80 [kvm] [c0002003591abd20] [c0000000006ebb58] ksys_ioctl+0x188/0x210 [c0002003591abd70] [c0000000006ebc28] sys_ioctl+0x48/0xb0 [c0002003591abdb0] [c000000000042764] system_call_exception+0x1d4/0x2e0 [c0002003591abe20] [c00000000000cce8] system_call_common+0xe8/0x214 Signed-off-by: Alexey Kardashevskiy --- arch/powerpc/kvm/book3s_64_mmu_radix.c | 4 ++++ arch/powerpc/kvm/book3s_hv_nested.c | 30 ++++++++++++++++---------- arch/powerpc/kvm/book3s_rtas.c | 2 ++ arch/powerpc/kvm/powerpc.c | 5 ++++- 4 files changed, 29 insertions(+), 12 deletions(-) diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c index aa12cd4078b3..ef7fcc2e7c96 100644 --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c @@ -160,7 +160,9 @@ int kvmppc_mmu_walk_radix_tree(struct kvm_vcpu *vcpu, gva_t eaddr, return -EINVAL; /* Read the entry from guest memory */ addr = base + (index * sizeof(rpte)); + vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); ret = kvm_read_guest(kvm, addr, &rpte, sizeof(rpte)); + srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx); if (ret) { if (pte_ret_p) *pte_ret_p = addr; @@ -236,7 +238,9 @@ int kvmppc_mmu_radix_translate_table(struct kvm_vcpu *vcpu, gva_t eaddr, /* Read the table to find the root of the radix tree */ ptbl = (table & PRTB_MASK) + (table_index * sizeof(entry)); + vcpu->srcu_idx = srcu_read_lock(&kvm->srcu); ret = kvm_read_guest(kvm, ptbl, &entry, sizeof(entry)); + srcu_read_unlock(&kvm->srcu, vcpu->srcu_idx); if (ret) return ret; diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c index dc97e5be76f6..1d3ab6fb00a7 100644 --- a/arch/powerpc/kvm/book3s_hv_nested.c +++ b/arch/powerpc/kvm/book3s_hv_nested.c @@ -233,20 +233,21 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu) /* copy parameters in */ hv_ptr = kvmppc_get_gpr(vcpu, 4); + regs_ptr = kvmppc_get_gpr(vcpu, 5); + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); err = kvm_vcpu_read_guest(vcpu, hv_ptr, &l2_hv, - sizeof(struct hv_guest_state)); + sizeof(struct hv_guest_state)) || + kvm_vcpu_read_guest(vcpu, regs_ptr, &l2_regs, + sizeof(struct pt_regs)); + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); if (err) return H_PARAMETER; + if (kvmppc_need_byteswap(vcpu)) byteswap_hv_regs(&l2_hv); if (l2_hv.version != HV_GUEST_STATE_VERSION) return H_P2; - regs_ptr = kvmppc_get_gpr(vcpu, 5); - err = kvm_vcpu_read_guest(vcpu, regs_ptr, &l2_regs, - sizeof(struct pt_regs)); - if (err) - return H_PARAMETER; if (kvmppc_need_byteswap(vcpu)) byteswap_pt_regs(&l2_regs); if (l2_hv.vcpu_token >= NR_CPUS) @@ -324,12 +325,12 @@ long kvmhv_enter_nested_guest(struct kvm_vcpu *vcpu) byteswap_hv_regs(&l2_hv); byteswap_pt_regs(&l2_regs); } + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); err = kvm_vcpu_write_guest(vcpu, hv_ptr, &l2_hv, - sizeof(struct hv_guest_state)); - if (err) - return H_AUTHORITY; - err = kvm_vcpu_write_guest(vcpu, regs_ptr, &l2_regs, + sizeof(struct hv_guest_state)) || + kvm_vcpu_write_guest(vcpu, regs_ptr, &l2_regs, sizeof(struct pt_regs)); + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); if (err) return H_AUTHORITY; @@ -509,12 +510,16 @@ long kvmhv_copy_tofrom_guest_nested(struct kvm_vcpu *vcpu) goto not_found; /* Write what was loaded into our buffer back to the L1 guest */ + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); rc = kvm_vcpu_write_guest(vcpu, gp_to, buf, n); + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); if (rc) goto not_found; } else { /* Load the data to be stored from the L1 guest into our buf */ + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); rc = kvm_vcpu_read_guest(vcpu, gp_from, buf, n); + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); if (rc) goto not_found; @@ -549,9 +554,12 @@ static void kvmhv_update_ptbl_cache(struct kvm_nested_guest *gp) ret = -EFAULT; ptbl_addr = (kvm->arch.l1_ptcr & PRTB_MASK) + (gp->l1_lpid << 4); - if (gp->l1_lpid < (1ul << ((kvm->arch.l1_ptcr & PRTS_MASK) + 8))) + if (gp->l1_lpid < (1ul << ((kvm->arch.l1_ptcr & PRTS_MASK) + 8))) { + int srcu_idx = srcu_read_lock(&kvm->srcu); ret = kvm_read_guest(kvm, ptbl_addr, &ptbl_entry, sizeof(ptbl_entry)); + srcu_read_unlock(&kvm->srcu, srcu_idx); + } if (ret) { gp->l1_gr_to_hr = 0; gp->process_table = 0; diff --git a/arch/powerpc/kvm/book3s_rtas.c b/arch/powerpc/kvm/book3s_rtas.c index 26b25994c969..c5e677508d3b 100644 --- a/arch/powerpc/kvm/book3s_rtas.c +++ b/arch/powerpc/kvm/book3s_rtas.c @@ -229,7 +229,9 @@ int kvmppc_rtas_hcall(struct kvm_vcpu *vcpu) */ args_phys = kvmppc_get_gpr(vcpu, 4) & KVM_PAM; + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); rc = kvm_read_guest(vcpu->kvm, args_phys, &args, sizeof(args)); + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); if (rc) goto fail; diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c index e15166b0a16d..2c3a1c799e14 100644 --- a/arch/powerpc/kvm/powerpc.c +++ b/arch/powerpc/kvm/powerpc.c @@ -403,7 +403,10 @@ int kvmppc_ld(struct kvm_vcpu *vcpu, ulong *eaddr, int size, void *ptr, return EMULATE_DONE; } - if (kvm_read_guest(vcpu->kvm, pte.raddr, ptr, size)) + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); + rc = kvm_read_guest(vcpu->kvm, pte.raddr, ptr, size); + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); + if (rc) return EMULATE_DO_MMIO; return EMULATE_DONE;