From: "Michael S. Tsirkin" <mst@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Andrew Baumann" <Andrew.Baumann@microsoft.com>,
"Aurelien Jarno" <aurelien@aurel32.net>,
kvm-devel <kvm@vger.kernel.org>,
"Alex Williamson" <alex.williamson@redhat.com>,
"Aleksandar Markovic" <amarkovic@wavecomp.com>,
"Joel Stanley" <joel@jms.id.au>, qemu-arm <qemu-arm@nongnu.org>,
"Marcelo Tosatti" <mtosatti@redhat.com>,
"Alistair Francis" <alistair@alistair23.me>,
"Eduardo Habkost" <ehabkost@redhat.com>,
"Richard Henderson" <rth@twiddle.net>,
"Aleksandar Rikalo" <aleksandar.rikalo@rt-rk.com>,
"Paul Burton" <pburton@wavecomp.com>,
"Marcel Apfelbaum" <marcel.apfelbaum@gmail.com>,
"Edgar E. Iglesias" <edgar.iglesias@gmail.com>,
"Paolo Bonzini" <pbonzini@redhat.com>
Subject: Re: [PATCH 0/8] Simplify memory_region_add_subregion_overlap(..., priority=0)
Date: Sun, 15 Dec 2019 04:54:42 -0500 [thread overview]
Message-ID: <20191215045230-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAFEAcA-UdDF2pd24NoOqpXSTnHHFWdvcexi5bRzq6ewt5vrrWQ@mail.gmail.com>
On Sat, Dec 14, 2019 at 08:01:46PM +0000, Peter Maydell wrote:
> On Sat, 14 Dec 2019 at 18:17, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> > Maybe we can a warning if priority=0, to force board designers to use
> > explicit priority (explicit overlap).
>
> Priority 0 is fine, it's just one of the possible positive and
> negative values. I think what ideally we would complain about
> is where we see an overlap and both the regions involved
> have the same priority value, because in that case which
> one the guest sees is implicitly dependent on (I think) which
> order the subregions were added, which is fragile if we move
> code around. I'm not sure how easy that is to test for or how
> much of our existing code violates it, though.
>
> thanks
> -- PMM
Problem is it's not uncommon for guests to create such
configs, and then just never access them.
So the thing to do would be to complain *on access*.
--
MST
WARNING: multiple messages have this Message-ID (diff)
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 04:54:42 -0500 [thread overview]
Message-ID: <20191215045230-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAFEAcA-UdDF2pd24NoOqpXSTnHHFWdvcexi5bRzq6ewt5vrrWQ@mail.gmail.com>
On Sat, Dec 14, 2019 at 08:01:46PM +0000, Peter Maydell wrote:
> On Sat, 14 Dec 2019 at 18:17, Philippe Mathieu-Daudé <philmd@redhat.com> wrote:
> > Maybe we can a warning if priority=0, to force board designers to use
> > explicit priority (explicit overlap).
>
> Priority 0 is fine, it's just one of the possible positive and
> negative values. I think what ideally we would complain about
> is where we see an overlap and both the regions involved
> have the same priority value, because in that case which
> one the guest sees is implicitly dependent on (I think) which
> order the subregions were added, which is fragile if we move
> code around. I'm not sure how easy that is to test for or how
> much of our existing code violates it, though.
>
> thanks
> -- PMM
Problem is it's not uncommon for guests to create such
configs, and then just never access them.
So the thing to do would be to complain *on access*.
--
MST
next prev parent reply other threads:[~2019-12-15 9:54 UTC|newest]
Thread overview: 34+ 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 ` 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 ` Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 2/8] hw/arm/raspi: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 3/8] hw/arm/xlnx-versal: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` 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 ` 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 ` Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 6/8] hw/vfio/pci: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` Philippe Mathieu-Daudé
2019-12-14 15:56 ` [PATCH 7/8] target/i386: " Philippe Mathieu-Daudé
2019-12-14 15:56 ` 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 15:56 ` Philippe Mathieu-Daudé
2019-12-14 16:28 ` [PATCH 0/8] Simplify memory_region_add_subregion_overlap(..., priority=0) Peter Maydell
2019-12-14 16:28 ` Peter Maydell
2019-12-14 18:17 ` Philippe Mathieu-Daudé
2019-12-14 18:17 ` Philippe Mathieu-Daudé
2019-12-14 20:01 ` Peter Maydell
2019-12-14 20:01 ` Peter Maydell
2019-12-15 9:54 ` Michael S. Tsirkin [this message]
2019-12-15 9:54 ` Michael S. Tsirkin
2019-12-15 9:51 ` Michael S. Tsirkin
2019-12-15 9:51 ` Michael S. Tsirkin
2019-12-15 15:27 ` Peter Maydell
2019-12-15 15:27 ` Peter Maydell
2019-12-16 11:39 ` Michael S. Tsirkin
2019-12-16 11:39 ` Michael S. Tsirkin
2019-12-16 11:46 ` Peter Maydell
2019-12-16 11:46 ` Peter Maydell
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