On 2014/10/31 12:33, Wanpeng Li wrote:
The srcu read lock must be held while accessing memslots (e.g.
when using gfn_to_* functions), however, commit c24ae0dcd3e8
("kvm: x86: Unpin and remove kvm_arch->apic_access_page") call
gfn_to_page() in kvm_vcpu_reload_apic_access_page() w/o hold it
which leads to suspicious rcu_dereference_check() usage warning.
This patch fix it by holding srcu read lock when call gfn_to_page()
in kvm_vcpu_reload_apic_access_page() function.
[ INFO: suspicious RCU usage. ]
3.18.0-rc2-test2+ #70 Not tainted
-------------------------------
include/linux/kvm_host.h:474 suspicious rcu_dereference_check() usage!
other info that might help us debug this:
rcu_scheduler_active = 1, debug_locks = 0
1 lock held by qemu-system-x86/2371:
#0: (&vcpu->mutex){+.+...}, at: [<ffffffffa037d800>] vcpu_load+0x20/0xd0 [kvm]
stack backtrace:
CPU: 4 PID: 2371 Comm: qemu-system-x86 Not tainted 3.18.0-rc2-test2+ #70
Hardware name: Dell Inc. OptiPlex 9010/0M9KCM, BIOS A12 01/10/2013
0000000000000001 ffff880209983ca8 ffffffff816f514f 0000000000000000
ffff8802099b8990 ffff880209983cd8 ffffffff810bd687 00000000000fee00
ffff880208a2c000 ffff880208a10000 ffff88020ef50040 ffff880209983d08
Call Trace:
[<ffffffff816f514f>] dump_stack+0x4e/0x71
[<ffffffff810bd687>] lockdep_rcu_suspicious+0xe7/0x120
[<ffffffffa037d055>] gfn_to_memslot+0xd5/0xe0 [kvm]
[<ffffffffa03807d3>] __gfn_to_pfn+0x33/0x60 [kvm]
[<ffffffffa0380885>] gfn_to_page+0x25/0x90 [kvm]
[<ffffffffa038aeec>] kvm_vcpu_reload_apic_access_page+0x3c/0x80 [kvm]
[<ffffffffa08f0a9c>] vmx_vcpu_reset+0x20c/0x460 [kvm_intel]
[<ffffffffa039ab8e>] kvm_vcpu_reset+0x15e/0x1b0 [kvm]
[<ffffffffa039ac0c>] kvm_arch_vcpu_setup+0x2c/0x50 [kvm]
[<ffffffffa037f7e0>] kvm_vm_ioctl+0x1d0/0x780 [kvm]
[<ffffffff810bc664>] ? __lock_is_held+0x54/0x80
[<ffffffff812231f0>] do_vfs_ioctl+0x300/0x520
[<ffffffff8122ee45>] ? __fget+0x5/0x250
[<ffffffff8122f0fa>] ? __fget_light+0x2a/0xe0
[<ffffffff81223491>] SyS_ioctl+0x81/0xa0
[<ffffffff816fed6d>] system_call_fastpath+0x16/0x1b
Reported-by: Takashi Iwai <tiwai@xxxxxxx>
Reported-by: Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0033df3..2d97329 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6059,6 +6059,7 @@ static void kvm_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
{
struct page *page = NULL;
+ int idx;
if (!irqchip_in_kernel(vcpu->kvm))
return;
@@ -6066,7 +6067,9 @@ void kvm_vcpu_reload_apic_access_page(struct kvm_vcpu *vcpu)
if (!kvm_x86_ops->set_apic_access_page_addr)
return;
+ idx = srcu_read_lock(&vcpu->kvm->srcu);
There's another scenario that we already hold srcu before call
kvm_vcpu_reload_apic_access_page(),
__vcpu_run()
|
+ vcpu->srcu_idx = srcu_read_lock(&kvm->srcu);
+ r = vcpu_enter_guest(vcpu);
|
+ kvm_vcpu_reload_apic_access_page(vcpu);
So according to backtrace I think we should fix as follows:
kvm: x86: vmx: hold kvm->srcu while reload apic access page
kvm_vcpu_reload_apic_access_page() needs to access memslots via
gfn_to_page(), so its necessary to hold kvm->srcu.
Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
---
arch/x86/kvm/vmx.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index b25a588..9fa1f46 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4442,6 +4442,7 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
struct msr_data apic_base_msr;
+ int idx;
vmx->rmode.vm86_active = 0;
@@ -4509,7 +4510,9 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu)
vmcs_write32(TPR_THRESHOLD, 0);
}
+ idx = srcu_read_lock(&vcpu->kvm->srcu);
kvm_vcpu_reload_apic_access_page(vcpu);
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
if (vmx_vm_has_apicv(vcpu->kvm))
memset(&vmx->pi_desc, 0, sizeof(struct pi_desc));
--
1.9.1
Thanks
Tiejun
page = gfn_to_page(vcpu->kvm, APIC_DEFAULT_PHYS_BASE >> PAGE_SHIFT);
+ srcu_read_unlock(&vcpu->kvm->srcu, idx);
kvm_x86_ops->set_apic_access_page_addr(vcpu, page_to_phys(page));
/*
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
