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Date:   Tue, 31 May 2022 18:01:58 +0100
From:   Will Deacon <will@kernel.org>
To:     Qian Cai <quic_qiancai@quicinc.com>
Cc:     Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
        Alexandru Elisei <alexandru.elisei@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] KVM: arm64: Fix memory leaks from stage2 pagetable
Message-ID: <20220531170157.GC25631@willie-the-truck>
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 <20220531165710.GB25631@willie-the-truck>
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On Tue, May 31, 2022 at 05:57:11PM +0100, Will Deacon wrote:
> On Thu, May 26, 2022 at 04:39:56PM -0400, Qian Cai wrote:
> > Running some SR-IOV workloads could trigger some leak reports from
> > kmemleak.
> > 
> > unreferenced object 0xffff080243cef500 (size 128):
> >   comm "qemu-system-aar", pid 179935, jiffies 4298359506 (age 1629.732s)
> >   hex dump (first 32 bytes):
> >     28 00 00 00 01 00 00 00 00 e0 4c 52 03 08 ff ff  (.........LR....
> >     e0 af a4 7f 7c d1 ff ff a8 3c b3 08 00 80 ff ff  ....|....<......
> >   backtrace:
> >      kmem_cache_alloc_trace
> >      kvm_init_stage2_mmu
> 
> Hmm, I can't spot a 128-byte allocation in here so this is pretty cryptic.
> I don't really like the idea of papering over the report; we'd be better off
> trying to reproduce it.

... although the hexdump does look like {u32; u32; ptr; ptr; ptr}, which
would match 'struct kvm_pgtable'. I guess the allocation is aligned to
ARCH_DMA_MINALIGN, which could explain the size?

Have you spotted any pattern for when the leak occurs? How are you
terminating the guest?

Will