From: Peter Xu <peterx@redhat.com>
To: Nikunj A Dadhania <nikunj@amd.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
vasant.hegde@amd.com, brijesh.singh@amd.com
Subject: Re: [PATCH] KVM: x86: Do not create mmu_rmaps_stat for TDP MMU
Date: Tue, 4 Jan 2022 17:49:31 +0800 [thread overview]
Message-ID: <YdQYK4oRDU2Dmfwe@xz-m1.local> (raw)
In-Reply-To: <20220104092814.11553-1-nikunj@amd.com>
Hi, Nikunj,
On Tue, Jan 04, 2022 at 02:58:14PM +0530, Nikunj A Dadhania wrote:
> With TDP MMU being the default now, access to mmu_rmaps_stat debugfs
> file causes following oops:
>
> BUG: kernel NULL pointer dereference, address: 0000000000000000
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP NOPTI
> CPU: 7 PID: 3185 Comm: cat Not tainted 5.16.0-rc4+ #204
> RIP: 0010:pte_list_count+0x6/0x40
> Call Trace:
> <TASK>
> ? kvm_mmu_rmaps_stat_show+0x15e/0x320
> seq_read_iter+0x126/0x4b0
> ? aa_file_perm+0x124/0x490
> seq_read+0xf5/0x140
> full_proxy_read+0x5c/0x80
> vfs_read+0x9f/0x1a0
> ksys_read+0x67/0xe0
> __x64_sys_read+0x19/0x20
> do_syscall_64+0x3b/0xc0
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7fca6fc13912
>
> Create mmu_rmaps_stat debugfs file only when rmaps are created.
>
> Reported-by: Vasant Hegde <vasant.hegde@amd.com>
> Tested-by: Vasant Hegde <vasant.hegde@amd.com>
> Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Shall we put the check into kvm_mmu_rmaps_stat_show()? As iiuc the rmap can be
allocated dynamically (shadow_root_allocated changing from 0->1).
Thanks,
--
Peter Xu
next prev parent reply other threads:[~2022-01-04 9:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-04 9:28 Nikunj A Dadhania
2022-01-04 9:49 ` Peter Xu [this message]
2022-01-04 10:38 ` Nikunj A. Dadhania
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