From: David Edmondson <dme@dme.org>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
qemu-devel@nongnu.org, "Haibin Zhang" <haibinzhang@tencent.com>
Cc: Markus Armbruster <armbru@redhat.com>,
Laszlo Ersek <lersek@redhat.com>,
dgilbert@redhat.com, mst@redhat.com
Subject: Re: [PATCH] pci: add romsize property
Date: Wed, 20 Jan 2021 10:14:18 +0000 [thread overview]
Message-ID: <cun1ref9apx.fsf@dme.org> (raw)
In-Reply-To: <b9b7e55a-0f90-6680-8e15-992997afdd38@redhat.com>
On Tuesday, 2021-01-19 at 17:51:32 +01, Philippe Mathieu-Daudé wrote:
> +pflash
>
> On 12/18/20 7:27 PM, Paolo Bonzini wrote:
>> This property can be useful for distros to set up known-good ROM sizes for
>> migration purposes. The VM will fail to start if the ROM is too large,
>> and migration compatibility will not be broken if the ROM is too small.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>> hw/pci/pci.c | 19 +++++++++++++++++--
>> hw/xen/xen_pt_load_rom.c | 14 ++++++++++++--
>> include/hw/pci/pci.h | 1 +
>> 3 files changed, 30 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/pci/pci.c b/hw/pci/pci.c
>> index d4349ea577..fd25253c2a 100644
>> --- a/hw/pci/pci.c
>> +++ b/hw/pci/pci.c
>> @@ -67,6 +67,7 @@ static void pcibus_reset(BusState *qbus);
>> static Property pci_props[] = {
>> DEFINE_PROP_PCI_DEVFN("addr", PCIDevice, devfn, -1),
>> DEFINE_PROP_STRING("romfile", PCIDevice, romfile),
>> + DEFINE_PROP_UINT32("romsize", PCIDevice, romsize, -1),
>> DEFINE_PROP_UINT32("rombar", PCIDevice, rom_bar, 1),
>> DEFINE_PROP_BIT("multifunction", PCIDevice, cap_present,
>> QEMU_PCI_CAP_MULTIFUNCTION_BITNR, false),
>> @@ -2106,6 +2107,11 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
>> bool is_default_rom;
>> uint16_t class_id;
>>
>> + if (pci_dev->romsize != -1 && !is_power_of_2(pci_dev->romsize)) {
>> + error_setg(errp, "ROM size %d is not a power of two", pci_dev->romsize);
>> + return;
>> + }
>
> Some cloud providers already complained the pow2 check in the pflash
> device (wasting host storage). Personally I find using pow2 easier
> and safer.
>
> The pow2 check looks like a separate change however, maybe add in a
> separate patch? Or maybe not :)
Even for flash, padding a read-only device seems straightforward.
For a writable device, is it assumed that a write into the padding
should extend the file?
(I realise that this patch is just for the ROM.)
dme.
--
You bring light in.
next prev parent reply other threads:[~2021-01-20 10:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 18:27 [PATCH] pci: add romsize property Paolo Bonzini
2020-12-18 18:54 ` Dr. David Alan Gilbert
2021-01-19 16:31 ` Peter Xu
2021-01-19 16:51 ` Philippe Mathieu-Daudé
2021-01-19 17:10 ` Paolo Bonzini
2021-01-19 17:19 ` Philippe Mathieu-Daudé
2021-01-19 17:20 ` Laszlo Ersek
2021-01-22 14:54 ` Paolo Bonzini
2021-01-20 10:14 ` David Edmondson [this message]
2021-01-22 14:30 ` Michael S. Tsirkin
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