From a1ac5f0943019bfd76345fe05a42cbc400da685c Mon Sep 17 00:00:00 2001
From: Weinan Li <weinan.z.li@intel.com>
Date: Mon, 17 Sep 2018 09:46:14 +0800
Subject: [PATCH] drm/i915/gvt: request srcu_read_lock before checking if one gfn is valid
Git-commit: a1ac5f0943019bfd76345fe05a42cbc400da685c
Patch-mainline: v4.19-rc5
References: bsc#1051510
Fix the suspicious RCU usage issue in intel_vgpu_emulate_mmio_write.
Here need to request the srcu read lock of kvm->srcu before doing
gfn_to_memslot(). The detailed log is as below:
[ 218.710688] =============================
[ 218.710690] WARNING: suspicious RCU usage
[ 218.710693] 4.14.15-dd+ #314 Tainted: G U
[ 218.710695] -----------------------------
[ 218.710697] ./include/linux/kvm_host.h:575 suspicious rcu_dereference_check() usage!
[ 218.710699]
other info that might help us debug this:
[ 218.710702]
rcu_scheduler_active = 2, debug_locks = 1
[ 218.710704] 1 lock held by qemu-system-x86/2144:
[ 218.710706] #0: (&gvt->lock){+.+.}, at: [<ffffffff816a1eea>] intel_vgpu_emulate_mmio_write+0x5a/0x2d0
[ 218.710721]
stack backtrace:
[ 218.710724] CPU: 0 PID: 2144 Comm: qemu-system-x86 Tainted: G U 4.14.15-dd+ #314
[ 218.710727] Hardware name: Dell Inc. OptiPlex 7040/0Y7WYT, BIOS 1.1.1 10/07/2015
[ 218.710729] Call Trace:
[ 218.710734] dump_stack+0x7c/0xb3
[ 218.710739] gfn_to_memslot+0x15f/0x170
[ 218.710743] kvm_is_visible_gfn+0xa/0x30
[ 218.710746] intel_vgpu_emulate_gtt_mmio_write+0x267/0x3c0
[ 218.710751] ? __mutex_unlock_slowpath+0x3b/0x260
[ 218.710754] intel_vgpu_emulate_mmio_write+0x182/0x2d0
[ 218.710759] intel_vgpu_rw+0xba/0x170 [kvmgt]
[ 218.710763] intel_vgpu_write+0x14d/0x1a0 [kvmgt]
[ 218.710767] __vfs_write+0x23/0x130
[ 218.710770] vfs_write+0xb0/0x1b0
[ 218.710774] SyS_pwrite64+0x73/0x90
[ 218.710777] entry_SYSCALL_64_fastpath+0x25/0x9c
[ 218.710780] RIP: 0033:0x7f33e8a91da3
[ 218.710783] RSP: 002b:00007f33dddc8700 EFLAGS: 00000293
V2: add 'Fixes' tag, refine log format.(Zhenyu)
Fixes: cc753fbe1ac4 ("drm/i915/gvt: validate gfn before set shadow page")
Reviewed-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Weinan Li <weinan.z.li@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/gvt/kvmgt.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/drivers/gpu/drm/i915/gvt/kvmgt.c
+++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
@@ -1833,6 +1833,8 @@ static bool kvmgt_is_valid_gfn(unsigned
{
struct kvmgt_guest_info *info;
struct kvm *kvm;
+ int idx;
+ bool ret;
if (!handle_valid(handle))
return false;
@@ -1840,8 +1842,11 @@ static bool kvmgt_is_valid_gfn(unsigned
info = (struct kvmgt_guest_info *)handle;
kvm = info->kvm;
- return kvm_is_visible_gfn(kvm, gfn);
+ idx = srcu_read_lock(&kvm->srcu);
+ ret = kvm_is_visible_gfn(kvm, gfn);
+ srcu_read_unlock(&kvm->srcu, idx);
+ return ret;
}
struct intel_gvt_mpt kvmgt_mpt = {