Re: [RFT][PATCH v2 5/9] vfio/ap: Remove redundant pfn

Jason Gunthorpe
2022-07-06T17:55:24Z

On Tue, Jul 05, 2022 at 11:27:55PM -0700, Nicolin Chen wrote:
> The vfio_ap_ops code maintains both nib address and its PFN, which
> is redundant, merely because vfio_pin/unpin_pages API wanted pfn.
> Since vfio_pin/unpin_pages() now accept "iova", remove duplicated
> pfn code in their callers too.

I would describe this as renaming saved_pfn to saved_iova

> *
> * @vcpu: the object representing the vcpu executing the PQAP(AQIC) instruction.
> * @nib: the location for storing the nib address.
> - * @g_pfn: the location for storing the page frame number of the page containing
> - * the nib.
> *
> * When the PQAP(AQIC) instruction is executed, general register 2 contains the
> * address of the notification indicator byte (nib) used for IRQ notification.
> - * This function parses the nib from gr2 and calculates the page frame
> - * number for the guest of the page containing the nib. The values are
> - * stored in @nib and @g_pfn respectively.
> - *
> - * The g_pfn of the nib is then validated to ensure the nib address is valid.
> + * This function parses and validate the nib from gr2.
> *
> * Return: returns zero if the nib address is a valid; otherwise, returns
> * -EINVAL.
> */
> -static int vfio_ap_validate_nib(struct kvm_vcpu *vcpu, unsigned long *nib,
> - unsigned long *g_pfn)
> +static int vfio_ap_validate_nib(struct kvm_vcpu *vcpu, dma_addr_t *nib)
> {
> *nib = vcpu->run->s.regs.gprs[2];
> - *g_pfn = *nib >> PAGE_SHIFT;
>
> - if (kvm_is_error_hva(gfn_to_hva(vcpu->kvm, *g_pfn)))
> + if (kvm_is_error_hva(gfn_to_hva(vcpu->kvm, *nib >> PAGE_SHIFT)))
> return -EINVAL;

This existing code is fishy. nib is either an IOVA passed to
vfio_pin_pages() or a GFN passed to gfn_to_hva(). These are not the
same thing and are not interchangable - writing code like this assumes
that the guest is running with iommu=pt or no iommu.

Someone should look at it..

Otherwise it looks OK

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

Jason