From: "Michael S. Tsirkin" <mst@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Paul Burton" <pburton@wavecomp.com>,
"Alistair Francis" <alistair@alistair23.me>,
"Eduardo Habkost" <ehabkost@redhat.com>,
kvm-devel <kvm@vger.kernel.org>,
"Marcelo Tosatti" <mtosatti@redhat.com>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Andrew Baumann" <Andrew.Baumann@microsoft.com>,
"Alex Williamson" <alex.williamson@redhat.com>,
qemu-arm <qemu-arm@nongnu.org>, "Joel Stanley" <joel@jms.id.au>,
"Aleksandar Markovic" <amarkovic@wavecomp.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
"Aleksandar Rikalo" <aleksandar.rikalo@rt-rk.com>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Aurelien Jarno" <aurelien@aurel32.net>,
"Richard Henderson" <rth@twiddle.net>
Subject: Re: [PATCH 0/8] Simplify memory_region_add_subregion_overlap(..., priority=0)
Date: Sun, 15 Dec 2019 04:51:42 -0500 [thread overview]
Message-ID: <20191215044759-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAFEAcA_QZtU9X4fxZk2oWAkN-zxXdQZejrSKZbDxPKLMwdFWgw@mail.gmail.com>
On Sat, Dec 14, 2019 at 04:28:08PM +0000, Peter Maydell wrote:
> (It doesn't actually assert that it doesn't
> overlap because we have some legacy uses, notably
> in the x86 PC machines, which do overlap without using
> the right function, which we've never tried to tidy up.)
It's not exactly legacy uses.
To be more exact, the way the non overlap versions
are *used* is to mean "I don't care what happens when they overlap"
as opposed to "will never overlap".
There are lots of regions where guest can make things overlapping
but doesn't, e.g. PCI BARs can be programmed to overlap
almost anything.
What happens on real hardware if you then access one of
the BARs is undefined, but programming itself is harmless.
That's why we can't assert.
--
MST
next prev parent reply other threads:[~2019-12-15 9:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-14 15:56 [PATCH 0/8] Simplify memory_region_add_subregion_overlap(..., priority=0) Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 1/8] hw/arm/nrf51_soc: Use memory_region_add_subregion() when priority is 0 Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 2/8] hw/arm/raspi: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 3/8] hw/arm/xlnx-versal: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 4/8] hw/i386/intel_iommu: Use memory_region_add_subregion " Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 5/8] hw/mips/boston: Use memory_region_add_subregion() " Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 6/8] hw/vfio/pci: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 7/8] target/i386: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 8/8] target/i386/cpu: Use 'mr' for MemoryRegion variables Philippe Mathieu-Daudé
2019-12-14 16:28 ` [PATCH 0/8] Simplify memory_region_add_subregion_overlap(..., priority=0) Peter Maydell
2019-12-14 18:17 ` Philippe Mathieu-Daudé
2019-12-14 20:01 ` Peter Maydell
2019-12-15 9:54 ` Michael S. Tsirkin
2019-12-15 9:51 ` Michael S. Tsirkin [this message]
2019-12-15 15:27 ` Peter Maydell
2019-12-16 11:39 ` Michael S. Tsirkin
2019-12-16 11:46 ` Peter Maydell
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