From: Peter Maydell <peter.maydell@linaro.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: QEMU Developers <qemu-devel@nongnu.org>,
qemu-stable <qemu-stable@nongnu.org>,
Richard Henderson <rth@twiddle.net>,
Stuart Monteith <stuart.monteith@linaro.org>
Subject: Re: [Qemu-devel] [PATCH v2 for-2.11 0/2] Fix TCG atomic writes to nondirty pages
Date: Tue, 21 Nov 2017 12:47:52 +0000 [thread overview]
Message-ID: <CAFEAcA8u5J+bEjp+Rq+n9W4WoJOXzTtHxKhVvUHp92isquE99g@mail.gmail.com> (raw)
In-Reply-To: <f5cc649a-8b33-fc0c-4a9c-559a33cda86b@redhat.com>
On 20 November 2017 at 20:54, Paolo Bonzini <pbonzini@redhat.com> wrote:
> On 20/11/2017 19:08, Peter Maydell wrote:
>> To do a write to memory that is marked as notdirty, we need
>> to invalidate any TBs we have cached for that memory, and
>> update the cpu physical memory dirty flags for VGA and migration.
>> The slowpath code in notdirty_mem_write() does all this correctly,
>> but the new atomic handling code in atomic_mmu_lookup() doesn't
>> do anything at all, it just clears the dirty bit in the TLB.
>>
>> The effect of this bug is that if the first write to a notdirty
>> page for which we have cached TBs is by a guest atomic access,
>> we fail to invalidate the TBs and subsequently will execute
>> incorrect code. This can be seen by trying to run 'javac' on AArch64.
>>
>> The first patch here refactors notdirty_mem_write() to pull out
>> the "correctly handle dirty bit updates" parts of the code into
>> two new functions memory_notdirty_write_prepare() and
>> memory_notdirty_write_complete(). The second patch then uses
>> those functions to fix the atomic helpers.
>
> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Thanks; applied to master for rc2.
-- PMM
prev parent reply other threads:[~2017-11-21 12:48 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-20 18:08 [Qemu-devel] [PATCH v2 for-2.11 0/2] Fix TCG atomic writes to nondirty pages Peter Maydell
2017-11-20 18:08 ` [Qemu-devel] [PATCH v2 for-2.11 1/2] exec.c: Factor out before/after actions for notdirty memory writes Peter Maydell
2017-11-20 18:08 ` [Qemu-devel] [PATCH v2 for-2.11 2/2] accel/tcg: Handle atomic accesses to notdirty memory correctly Peter Maydell
2017-11-20 21:30 ` Richard Henderson
2017-11-20 20:54 ` [Qemu-devel] [PATCH v2 for-2.11 0/2] Fix TCG atomic writes to nondirty pages Paolo Bonzini
2017-11-21 12:47 ` Peter Maydell [this message]
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