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Re: [Qemu-devel] [PATCH 1/4] hw/pcie: fix Extended Configuration Space f
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 1/4] hw/pcie: fix Extended Configuration Space for devices with no Extended Capabilities |
Date: |
Tue, 10 Jan 2017 05:13:07 +0200 |
On Wed, Jan 04, 2017 at 09:57:15PM +0200, Marcel Apfelbaum wrote:
> Absence of any Extended Capabilities is required to be
> indicated by an Extended Capability header with a Capability ID of
> 0000h, a Capability Version of 0h, and a Next Capability Offset of 000h.
>
> Instead of inserting a 'NULL' capability is simpler to mark the start
> of the Extended Configuration Space as read-only to achieve the same
> behaviour.
>
> Signed-off-by: Marcel Apfelbaum <address@hidden>
Kind of hacky and only theoretical - I don't think any guest writes
there - but ok. However I think
1. we should init config to 0 too
2. this needs a compat flag
> ---
> hw/pci/pcie.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/hw/pci/pcie.c b/hw/pci/pcie.c
> index 99cfb45..62c1def 100644
> --- a/hw/pci/pcie.c
> +++ b/hw/pci/pcie.c
> @@ -109,6 +109,9 @@ int pcie_cap_init(PCIDevice *dev, uint8_t offset, uint8_t
> type, uint8_t port)
> PCI_EXP_DEVCAP2_EFF | PCI_EXP_DEVCAP2_EETLPP);
>
> pci_set_word(dev->wmask + pos + PCI_EXP_DEVCTL2,
> PCI_EXP_DEVCTL2_EETLPPB);
> +
> + /* read-only to behave like a 'NULL' Extended Capability Header */
> + pci_set_long(dev->wmask + PCI_CONFIG_SPACE_SIZE, 0);
> return pos;
> }
>
> --
> 2.5.5