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Re: [Qemu-devel] [PATCH] Align PCI capabilities in pci_find_space
From: |
Alex Williamson |
Subject: |
Re: [Qemu-devel] [PATCH] Align PCI capabilities in pci_find_space |
Date: |
Tue, 25 Sep 2012 15:37:40 -0600 |
On Tue, 2012-09-25 at 15:59 -0500, address@hidden wrote:
> From: Matt Renzelmann <address@hidden>
>
> The current implementation of pci_find_space does not properly align
> PCI capabilities in the PCI configuration space. This patch fixes
> this issue.
>
> Signed-off-by: Matt Renzelmann <address@hidden>
> ---
>
> This is my first patch to QEMU so I hope I'm not screwing up too much.
> The purpose of this patch is to mask off the low-order two bits--Linux
> masks these while scanning the PCI configuration space, for example,
> so we need to make sure QEMU's behavior matches the standard.
>
> No current QEMU hardware is likely using this but it may be important
> later.
>
> hw/pci.c | 14 ++++++++++----
> 1 files changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/hw/pci.c b/hw/pci.c
> index e149305..8771b7e 100644
> --- a/hw/pci.c
> +++ b/hw/pci.c
> @@ -1571,11 +1571,17 @@ static int pci_find_space(PCIDevice *pdev, uint8_t
> size)
> int config_size = pci_config_size(pdev);
> int offset = PCI_CONFIG_HEADER_SIZE;
> int i;
> - for (i = PCI_CONFIG_HEADER_SIZE; i < config_size; ++i)
> - if (pdev->used[i])
> - offset = i + 1;
> - else if (i - offset + 1 == size)
> + int masked;
> +
> + for (i = PCI_CONFIG_HEADER_SIZE; i < config_size; ++i) {
> + masked = i & (~3);
> + if (pdev->used[i]) {
> + offset = masked + 4;
> + } else if (i - offset + 1 == size) {
> return offset;
> + }
> + }
> +
> return 0;
> }
>
I think you could just search every 4th byte. In fact, this whole used
byte-map could be turned into a single uint64_t bitmap for standard
config space. Thanks,
Alex