Re: [PATCH v9] vpci: Add resizable bar support

["Roger Pau Monné" <roger.pau@citrix.com>]

On Mon, Feb 24, 2025 at 11:24:33AM +0800, Jiqian Chen wrote:
> Some devices, like AMDGPU, support resizable bar capability,
> but vpci of Xen doesn't support this feature, so they fail
> to resize bars and then cause probing failure.
> 
> According to PCIe spec, each bar that supports resizing has
> two registers, PCI_REBAR_CAP and PCI_REBAR_CTRL. So, add
> handlers to support resizing the size of BARs.
> 
> Note that Xen will only trap PCI_REBAR_CTRL, as PCI_REBAR_CAP
> is read-only register and the hardware domain already gets
> access to it without needing any setup.
> 
> Signed-off-by: Jiqian Chen <Jiqian.Chen@amd.com>

Reviewed-by: Roger Pau Monné <roger.pau@cirtrix.com>

Just one question below about a cosmetic adjustment.

> diff --git a/xen/include/xen/pci_regs.h b/xen/include/xen/pci_regs.h
> index 250ba106dbd3..2f1d0d63e962 100644
> --- a/xen/include/xen/pci_regs.h
> +++ b/xen/include/xen/pci_regs.h
> @@ -459,6 +459,7 @@
>  #define PCI_EXT_CAP_ID_ARI	14
>  #define PCI_EXT_CAP_ID_ATS	15
>  #define PCI_EXT_CAP_ID_SRIOV	16
> +#define PCI_EXT_CAP_ID_REBAR	21	/* Resizable BAR */
>  
>  /* Advanced Error Reporting */
>  #define PCI_ERR_UNCOR_STATUS	4	/* Uncorrectable Error Status */
> @@ -541,6 +542,20 @@
>  #define  PCI_VNDR_HEADER_REV(x)	(((x) >> 16) & 0xf)
>  #define  PCI_VNDR_HEADER_LEN(x)	(((x) >> 20) & 0xfff)
>  
> +/* Resizable BARs */
> +#define PCI_REBAR_CAP(n)	(4 + 8 * (n))	/* capability register */
> +#define  PCI_REBAR_CAP_SIZES_MASK	0xFFFFFFF0U	/* supported BAR sizes in CAP */
> +#define PCI_REBAR_CTRL(n)	(8 + 8 * (n))	/* control register */
> +#define  PCI_REBAR_CTRL_BAR_IDX		0x00000007	/* BAR index */
> +#define  PCI_REBAR_CTRL_NBAR_MASK	0x000000E0	/* # of resizable BARs */
> +#define  PCI_REBAR_CTRL_BAR_SIZE	0x00003F00	/* BAR size */
> +#define  PCI_REBAR_CTRL_SIZES_MASK	0xFFFF0000U	/* supported BAR sizes in CTRL */
> +
> +#define PCI_REBAR_CTRL_SIZE_BIAS	20
> +#define PCI_REBAR_CTRL_SIZE(v) \
> +    (1ULL << (MASK_EXTR(v, PCI_REBAR_CTRL_BAR_SIZE) \
> +                      + PCI_REBAR_CTRL_SIZE_BIAS))

I think this could fit on a single line if the indent was just 4
spaces.  Would you mind me adjusting it at commit if it fits?

Thanks, Roger.