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Re: [PATCH 5/6] block/nvme: Align block pages queue to host page size
From: |
Laurent Vivier |
Subject: |
Re: [PATCH 5/6] block/nvme: Align block pages queue to host page size |
Date: |
Tue, 5 May 2020 10:23:25 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 |
On 05/05/2020 10:00, Laurent Vivier wrote:
> On 04/05/2020 11:46, Philippe Mathieu-Daudé wrote:
>> In nvme_create_queue_pair() we create a page list using
>> qemu_blockalign(), then map it with qemu_vfio_dma_map():
>>
>> q->prp_list_pages = qemu_blockalign0(bs, s->page_size * NVME_QUEUE_SIZE);
>> r = qemu_vfio_dma_map(s->vfio, q->prp_list_pages,
>> s->page_size * NVME_QUEUE_SIZE, ...);
>>
>> With:
>>
>> s->page_size = MAX(4096, 1 << (12 + ((cap >> 48) & 0xF)));
>>
>> The qemu_vfio_dma_map() documentation says "The caller need
>> to make sure the area is aligned to page size". While we use
>> multiple s->page_size as alignment, it might be not sufficient
>> on some hosts. Use the qemu_real_host_page_size value to be
>> sure the host alignment is respected.
>>
>> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
>> ---
>> Cc: Cédric Le Goater <address@hidden>
>> Cc: David Gibson <address@hidden>
>> Cc: Laurent Vivier <address@hidden>
>> ---
>> block/nvme.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/block/nvme.c b/block/nvme.c
>> index 7b7c0cc5d6..bde0d28b39 100644
>> --- a/block/nvme.c
>> +++ b/block/nvme.c
>> @@ -627,7 +627,7 @@ static int nvme_init(BlockDriverState *bs, const char
>> *device, int namespace,
>>
>> s->page_size = MAX(4096, 1 << (12 + ((cap >> 48) & 0xF)));
>> s->doorbell_scale = (4 << (((cap >> 32) & 0xF))) / sizeof(uint32_t);
>> - bs->bl.opt_mem_alignment = s->page_size;
>> + bs->bl.opt_mem_alignment = MAX(qemu_real_host_page_size, s->page_size);
>
> Why don't you replace directly the "4096" in s->page_size by
> qemu_real_host_page_size?
>
> I think this was the purpose of MAX(4096, ...) to align to the host page
> size.
oh, I see, page_size is used for a lot of things than can be broken, and
this is what is done in bdrv_opt_mem_align() for instance, 4096 is the
sector size not the host page size.
BTW, you need the same change as in nvme_init() in
nvme_refresh_limits(), I think.
Thanks,
Laurent
- Re: [PATCH 1/6] qemu/osdep: Document qemu_memalign() and friends, (continued)
- [PATCH 2/6] qemu/bitmap: Document bitmap_new() returned pointer, Philippe Mathieu-Daudé, 2020/05/04
- [PATCH 3/6] sysemu/block-backend: Document blk_read()/blk_pwrite(), Philippe Mathieu-Daudé, 2020/05/04
- [PATCH 4/6] block/block: Document BlockSizes fields, Philippe Mathieu-Daudé, 2020/05/04
- [PATCH 5/6] block/nvme: Align block pages queue to host page size, Philippe Mathieu-Daudé, 2020/05/04
- Re: [PATCH 5/6] block/nvme: Align block pages queue to host page size, Philippe Mathieu-Daudé, 2020/05/05
- [RFC PATCH 6/6] hw/block/nvme: Make device target agnostic, Philippe Mathieu-Daudé, 2020/05/04