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From:   Sudeep Holla <sudeep.holla@arm.com>
To:     kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
Cc:     Sudeep Holla <sudeep.holla@arm.com>, Will Deacon <will@kernel.org>,
        Marc Zyngier <maz@kernel.org>,
        Oliver Upton <oliver.upton@linux.dev>,
        James Morse <james.morse@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Zenghui Yu <yuzenghui@huawei.com>
Subject: [PATCH] KVM: arm64: Handle kvm_arm_init failure correctly in finalize_pkvm
Date:   Tue,  4 Jul 2023 20:32:43 +0100
Message-ID: <20230704193243.3300506-1-sudeep.holla@arm.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Currently there is no synchronisation between finalize_pkvm() and
kvm_arm_init() initcalls. The finalize_pkvm() proceeds happily even if
kvm_arm_init() fails resulting in the following warning on all the CPUs
and eventually a HYP panic:

  | kvm [1]: IPA Size Limit: 48 bits
  | kvm [1]: Failed to init hyp memory protection
  | kvm [1]: error initializing Hyp mode: -22
  |
  | <snip>
  |
  | WARNING: CPU: 0 PID: 0 at arch/arm64/kvm/pkvm.c:226 _kvm_host_prot_finalize+0x30/0x50
  | Modules linked in:
  | CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.0 #237
  | Hardware name: FVP Base RevC (DT)
  | pstate: 634020c5 (nZCv daIF +PAN -UAO +TCO +DIT -SSBS BTYPE=--)
  | pc : _kvm_host_prot_finalize+0x30/0x50
  | lr : __flush_smp_call_function_queue+0xd8/0x230
  |
  | Call trace:
  |  _kvm_host_prot_finalize+0x3c/0x50
  |  on_each_cpu_cond_mask+0x3c/0x6c
  |  pkvm_drop_host_privileges+0x4c/0x78
  |  finalize_pkvm+0x3c/0x5c
  |  do_one_initcall+0xcc/0x240
  |  do_initcall_level+0x8c/0xac
  |  do_initcalls+0x54/0x94
  |  do_basic_setup+0x1c/0x28
  |  kernel_init_freeable+0x100/0x16c
  |  kernel_init+0x20/0x1a0
  |  ret_from_fork+0x10/0x20
  | Failed to finalize Hyp protection: -22
  |     dtb=fvp-base-revc.dtb
  | kvm [95]: nVHE hyp BUG at: arch/arm64/kvm/hyp/nvhe/mem_protect.c:540!
  | kvm [95]: nVHE call trace:
  | kvm [95]:  [<ffff800081052984>] __kvm_nvhe_hyp_panic+0xac/0xf8
  | kvm [95]:  [<ffff800081059644>] __kvm_nvhe_handle_host_mem_abort+0x1a0/0x2ac
  | kvm [95]:  [<ffff80008105511c>] __kvm_nvhe_handle_trap+0x4c/0x160
  | kvm [95]:  [<ffff8000810540fc>] __kvm_nvhe___skip_pauth_save+0x4/0x4
  | kvm [95]: ---[ end nVHE call trace ]---
  | kvm [95]: Hyp Offset: 0xfffe8db00ffa0000
  | Kernel panic - not syncing: HYP panic:
  | PS:a34023c9 PC:0000f250710b973c ESR:00000000f2000800
  | FAR:ffff000800cb00d0 HPFAR:000000000880cb00 PAR:0000000000000000
  | VCPU:0000000000000000
  | CPU: 3 PID: 95 Comm: kworker/u16:2 Tainted: G        W          6.4.0 #237
  | Hardware name: FVP Base RevC (DT)
  | Workqueue: rpciod rpc_async_schedule
  | Call trace:
  |  dump_backtrace+0xec/0x108
  |  show_stack+0x18/0x2c
  |  dump_stack_lvl+0x50/0x68
  |  dump_stack+0x18/0x24
  |  panic+0x138/0x33c
  |  nvhe_hyp_panic_handler+0x100/0x184
  |  new_slab+0x23c/0x54c
  |  ___slab_alloc+0x3e4/0x770
  |  kmem_cache_alloc_node+0x1f0/0x278
  |  __alloc_skb+0xdc/0x294
  |  tcp_stream_alloc_skb+0x2c/0xf0
  |  tcp_sendmsg_locked+0x3d0/0xda4
  |  tcp_sendmsg+0x38/0x5c
  |  inet_sendmsg+0x44/0x60
  |  sock_sendmsg+0x1c/0x34
  |  xprt_sock_sendmsg+0xdc/0x274
  |  xs_tcp_send_request+0x1ac/0x28c
  |  xprt_transmit+0xcc/0x300
  |  call_transmit+0x78/0x90
  |  __rpc_execute+0x114/0x3d8
  |  rpc_async_schedule+0x28/0x48
  |  process_one_work+0x1d8/0x314
  |  worker_thread+0x248/0x474
  |  kthread+0xfc/0x184
  |  ret_from_fork+0x10/0x20
  | SMP: stopping secondary CPUs
  | Kernel Offset: 0x57c5cb460000 from 0xffff800080000000
  | PHYS_OFFSET: 0x80000000
  | CPU features: 0x00000000,1035b7a3,ccfe773f
  | Memory Limit: none
  | ---[ end Kernel panic - not syncing: HYP panic:
  | PS:a34023c9 PC:0000f250710b973c ESR:00000000f2000800
  | FAR:ffff000800cb00d0 HPFAR:000000000880cb00 PAR:0000000000000000
  | VCPU:0000000000000000 ]---

Fix it by checking for the successfull initialisation of kvm_arm_init()
in finalize_pkvm() before proceeding any futher.

Fixes: 87727ba2bb05 ("KVM: arm64: Ensure CPU PMU probes before pKVM host de-privilege")
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
---
 arch/arm64/include/asm/virt.h | 1 +
 arch/arm64/kvm/arm.c          | 9 ++++++++-
 arch/arm64/kvm/pkvm.c         | 2 +-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 5227db7640c8..261d6e9df2e1 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -78,6 +78,7 @@ extern u32 __boot_cpu_mode[2];
 
 void __hyp_set_vectors(phys_addr_t phys_vector_base);
 void __hyp_reset_vectors(void);
+bool is_kvm_arm_initialised(void);
 
 DECLARE_STATIC_KEY_FALSE(kvm_protected_mode_initialized);
 
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 173abca08b53..4e0176b44af3 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -53,11 +53,16 @@ DECLARE_KVM_NVHE_PER_CPU(struct kvm_nvhe_init_params, kvm_init_params);
 
 DECLARE_KVM_NVHE_PER_CPU(struct kvm_cpu_context, kvm_hyp_ctxt);
 
-static bool vgic_present;
+static bool vgic_present, kvm_arm_initialised;
 
 static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
 DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
 
+bool is_kvm_arm_initialised(void)
+{
+	return kvm_arm_initialised;
+}
+
 int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
 {
 	return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
@@ -2484,6 +2489,8 @@ static __init int kvm_arm_init(void)
 	if (err)
 		goto out_subs;
 
+	kvm_arm_initialised = true;
+
 	return 0;
 
 out_subs:
diff --git a/arch/arm64/kvm/pkvm.c b/arch/arm64/kvm/pkvm.c
index 994a494703c3..6ff3ec18c925 100644
--- a/arch/arm64/kvm/pkvm.c
+++ b/arch/arm64/kvm/pkvm.c
@@ -244,7 +244,7 @@ static int __init finalize_pkvm(void)
 {
 	int ret;
 
-	if (!is_protected_kvm_enabled())
+	if (!is_protected_kvm_enabled() || !is_kvm_arm_initialised())
 		return 0;
 
 	/*
-- 
2.41.0