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Re: [PATCH v3 2/2] hw/arm/virt: Support for virtio-mem-pci
From: |
Peter Maydell |
Subject: |
Re: [PATCH v3 2/2] hw/arm/virt: Support for virtio-mem-pci |
Date: |
Fri, 7 Jan 2022 16:40:23 +0000 |
On Fri, 3 Dec 2021 at 23:34, Gavin Shan <gshan@redhat.com> wrote:
>
> This supports virtio-mem-pci device on "virt" platform, by simply
> following the implementation on x86.
>
> * This implements the hotplug handlers to support virtio-mem-pci
> device hot-add, while the hot-remove isn't supported as we have
> on x86.
>
> * The block size is 512MB on ARM64 instead of 128MB on x86.
>
> * It has been passing the tests with various combinations like 64KB
> and 4KB page sizes on host and guest, different memory device
> backends like normal, transparent huge page and HugeTLB, plus
> migration.
>
> Co-developed-by: David Hildenbrand <david@redhat.com>
> Co-developed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> +static void virt_virtio_md_pci_pre_plug(HotplugHandler *hotplug_dev,
> + DeviceState *dev, Error **errp)
> +{
> + HotplugHandler *hotplug_dev2 = qdev_get_bus_hotplug_handler(dev);
> + Error *local_err = NULL;
> +
> + if (!hotplug_dev2 && dev->hotplugged) {
> + /*
> + * Without a bus hotplug handler, we cannot control the plug/unplug
> + * order. We should never reach this point when hotplugging on x86,
> + * however, better add a safety net.
> + */
This comment looks like it was cut-n-pasted from x86 -- is whatever
it is that prevents us from reaching this point also true for arm ?
(What is the thing that prevents us reaching this point?)
> + error_setg(errp, "hotplug of virtio based memory devices not
> supported"
> + " on this bus.");
> + return;
> + }
> + /*
> + * First, see if we can plug this memory device at all. If that
> + * succeeds, branch of to the actual hotplug handler.
> + */
> + memory_device_pre_plug(MEMORY_DEVICE(dev), MACHINE(hotplug_dev), NULL,
> + &local_err);
> + if (!local_err && hotplug_dev2) {
> + hotplug_handler_pre_plug(hotplug_dev2, dev, &local_err);
> + }
> + error_propagate(errp, local_err);
> +}
> diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
> index b20595a496..21e4d572ab 100644
> --- a/hw/virtio/virtio-mem.c
> +++ b/hw/virtio/virtio-mem.c
> @@ -125,7 +125,7 @@ static uint64_t virtio_mem_default_block_size(RAMBlock
> *rb)
> * The memory block size corresponds mostly to the section size.
> *
> * This allows e.g., to add 20MB with a section size of 128MB on x86_64, and
> - * a section size of 1GB on arm64 (as long as the start address is properly
> + * a section size of 512MB on arm64 (as long as the start address is properly
> * aligned, similar to ordinary DIMMs).
> *
> * We can change this at any time and maybe even make it configurable if
> @@ -134,6 +134,8 @@ static uint64_t virtio_mem_default_block_size(RAMBlock
> *rb)
> */
> #if defined(TARGET_X86_64) || defined(TARGET_I386)
> #define VIRTIO_MEM_USABLE_EXTENT (2 * (128 * MiB))
> +#elif defined(TARGET_ARM)
> +#define VIRTIO_MEM_USABLE_EXTENT (2 * (512 * MiB))
> #else
> #error VIRTIO_MEM_USABLE_EXTENT not defined
> #endif
Could this comment explain where the 128MB and 512MB come from
and why the value is different for different architectures ?
thanks
-- PMM
- Re: [PATCH v3 2/2] hw/arm/virt: Support for virtio-mem-pci,
Peter Maydell <=