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From: Stefan Hajnoczi <stefanha@gmail.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	"Jason Wang" <jasowang@redhat.com>,
	"Mark Cave-Ayland" <mark.cave-ayland@ilande.co.uk>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"Peter Xu" <peterx@redhat.com>,
	"Gerd Hoffmann" <kraxel@redhat.com>,
	"Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Edgar E . Iglesias" <edgar.iglesias@xilinx.com>,
	Qemu-block <qemu-block@nongnu.org>, "Li Qiang" <liq3ea@163.com>,
	"Emilio G . Cota" <cota@braap.org>,
	"Joel Stanley" <joel@jms.id.au>,
	"David Gibson" <david@gibson.dropbear.id.au>,
	"Laszlo Ersek" <lersek@redhat.com>,
	"Robert Foley" <robert.foley@linaro.org>,
	"Alistair Francis" <alistair@alistair23.me>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	"Beniamino Galvani" <b.galvani@gmail.com>,
	"Eric Auger" <eric.auger@redhat.com>,
	qemu-arm <qemu-arm@nongnu.org>,
	"Peter Chubb" <peter.chubb@nicta.com.au>,
	"Cédric Le Goater" <clg@kaod.org>,
	"Stefan Hajnoczi" <stefanha@redhat.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Richard Henderson" <rth@twiddle.net>,
	"Tony Nguyen" <tony.nguyen@bt.com>,
	"Prasad J Pandit" <pjp@fedoraproject.org>,
	"Alexander Bulekov" <alxndr@bu.edu>,
	"Andrew Jeffery" <andrew@aj.id.au>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>,
	"Emanuele Giuseppe Esposito" <e.emanuelegiuseppe@gmail.com>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	"Andrew Baumann" <Andrew.Baumann@microsoft.com>,
	qemu-ppc <qemu-ppc@nongnu.org>,
	"Klaus Jensen" <k.jensen@samsung.com>,
	"Jan Kiszka" <jan.kiszka@web.de>
Subject: Re: [RFC PATCH 00/12] hw: Forbid DMA write accesses to MMIO regions
Date: Wed, 9 Sep 2020 14:41:39 +0100	[thread overview]
Message-ID: <CAJSP0QUBR+6=rnQz-MJ3mPJ4TSqEme5SHHUP3dhnW4_y1dEf_w@mail.gmail.com> (raw)
In-Reply-To: <CAFEAcA-Ptc6_jQCna8+BMM1DOY-A+-b4toJiAm8z-9nzwJiDcg@mail.gmail.com>

On Wed, Sep 9, 2020 at 2:23 PM Peter Maydell <peter.maydell@linaro.org> wrote:
> On Wed, 9 Sep 2020 at 10:12, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> > On Thu, Sep 03, 2020 at 01:08:19PM +0200, Philippe Mathieu-Daudé wrote:
> > > The main patch is:
> > > "exec/memattrs: Introduce MemTxAttrs::direct_access field".
> > > This way we can restrict accesses to ROM/RAM by setting the
> > > 'direct_access' field. Illegal accesses return MEMTX_BUS_ERROR.
> >
> > QEMU needs to simulate the behavior of real hardware. What is the
> > behavior of real hardware?
>
> It varies, depending on the hardware. The most common thing
> is probably "happens to work by luck", which is OK for hardware
> but doesn't help us much since our software implementation is
> naturally more serialized than hardware is and since we don't
> want to allow guests to make QEMU crash or misbehave.

The memory API bounce buffer mechanism is evidence that some board(s)
need or needed it. At a minimum we need to find out the reason for the
bounce buffer mechanism to avoid breaking guests.

Stefan


      reply	other threads:[~2020-09-09 13:42 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-03 11:08 [RFC PATCH 00/12] hw: Forbid DMA write accesses to MMIO regions Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 01/12] pci: pass along the return value of dma_memory_rw Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 02/12] dma: Let dma_memory_valid() take MemTxAttrs argument Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 03/12] dma: Let dma_memory_set() " Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 04/12] dma: Let dma_memory_rw_relaxed() " Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 05/12] dma: Let dma_memory_rw() " Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 06/12] dma: Let dma_memory_read/write() " Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 07/12] dma: Let dma_memory_map() " Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 08/12] docs/devel/loads-stores: Add regexp for DMA functions Philippe Mathieu-Daudé
2020-09-03 11:08 ` [PATCH 09/12] dma: Let load/store DMA functions take MemTxAttrs argument Philippe Mathieu-Daudé
2020-09-03 11:08 ` [RFC PATCH 10/12] exec/memattrs: Introduce MemTxAttrs::direct_access field Philippe Mathieu-Daudé
2020-09-03 11:08 ` [RFC PATCH 11/12] hw/pci: Only allow PCI slave devices to write to direct memory Philippe Mathieu-Daudé
2020-09-03 12:26   ` Paolo Bonzini
2020-09-03 13:18     ` Philippe Mathieu-Daudé
2020-09-03 21:43       ` Paolo Bonzini
2020-09-03 11:08 ` [RFC PATCH 12/12] dma: Assert when device writes to indirect memory (such MMIO regions) Philippe Mathieu-Daudé
2020-09-03 13:51   ` Edgar E. Iglesias
2020-09-03 13:37 ` [RFC PATCH 00/12] hw: Forbid DMA write accesses to MMIO regions Laszlo Ersek
2020-09-03 13:58   ` Peter Maydell
2020-09-03 14:24     ` Edgar E. Iglesias
2020-09-03 15:46       ` Paolo Bonzini
2020-09-03 15:50         ` Edgar E. Iglesias
2020-09-03 17:53           ` Paolo Bonzini
2020-09-03 19:46             ` Edgar E. Iglesias
2020-09-04  2:50               ` Jason Wang
2020-09-05  2:27 ` Li Qiang
2020-09-08 14:37 ` Stefan Hajnoczi
2020-09-09 13:23   ` Peter Maydell
2020-09-09 13:41     ` Stefan Hajnoczi [this message]

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