On Sun, Mar 12, 2023 at 08:01:53PM +0800, Huang Rui wrote:
> Xen PVH is the paravirtualized mode and takes advantage of hardware
> virtualization support when possible. It will using the hardware IOMMU
> support instead of xen-swiotlb, so disable swiotlb if current domain is
> Xen PVH.
>
> Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> ---
> arch/x86/kernel/pci-dma.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
> index 30bbe4abb5d6..f5c73dd18f2a 100644
> --- a/arch/x86/kernel/pci-dma.c
> +++ b/arch/x86/kernel/pci-dma.c
> @@ -74,6 +74,12 @@ static inline void __init pci_swiotlb_detect(void)
> #ifdef CONFIG_SWIOTLB_XEN
> static void __init pci_xen_swiotlb_init(void)
> {
> + /* Xen PVH domain won't use swiotlb */
> + if (xen_pvh_domain()) {
> + x86_swiotlb_enable = false;
> + return;
> + }
I'm very confused by this: pci_xen_swiotlb_init() is only called for
PV domains, see the only caller in pci_iommu_alloc(). So this is just
dead code.
> +
> if (!xen_initial_domain() && !x86_swiotlb_enable)
> return;
> x86_swiotlb_enable = true;
> @@ -86,7 +92,7 @@ static void __init pci_xen_swiotlb_init(void)
>
> int pci_xen_swiotlb_init_late(void)
> {
> - if (dma_ops == &xen_swiotlb_dma_ops)
> + if (xen_pvh_domain() || dma_ops == &xen_swiotlb_dma_ops)
Same here, this function is only called by
pcifront_connect_and_init_dma() and pcifront should never attach on a
PVH domain, hence it's also dead code.
Thanks, Roger.
