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Re: [PATCH v6 10/13] vpci/header: reset the command register when adding devices
- To: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 4 Feb 2022 15:30:22 +0100
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- Cc: julien@xxxxxxx, sstabellini@xxxxxxxxxx, oleksandr_tyshchenko@xxxxxxxx, volodymyr_babchuk@xxxxxxxx, artem_mygaiev@xxxxxxxx, roger.pau@xxxxxxxxxx, andrew.cooper3@xxxxxxxxxx, george.dunlap@xxxxxxxxxx, paul@xxxxxxx, bertrand.marquis@xxxxxxx, rahul.singh@xxxxxxx, Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Fri, 04 Feb 2022 14:30:34 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 04.02.2022 07:34, Oleksandr Andrushchenko wrote:
> Reset the command register when assigning a PCI device to a guest:
> according to the PCI spec the PCI_COMMAND register is typically all 0's
> after reset.
It's not entirely clear to me whether setting the hardware register to
zero is okay. What wants to be zero is the value the guest observes
initially.
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -454,8 +454,7 @@ static void cmd_write(const struct pci_dev *pdev,
> unsigned int reg,
> pci_conf_write16(pdev->sbdf, reg, cmd);
> }
>
> -static void guest_cmd_write(const struct pci_dev *pdev, unsigned int reg,
> - uint32_t cmd, void *data)
> +static uint32_t emulate_cmd_reg(const struct pci_dev *pdev, uint32_t cmd)
The command register is a 16-bit one, so parameter and return type should
either be plain unsigned int (preferred, see ./CODING_STYLE) or uint16_t
imo.
Jan
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