Re: [PATCH v2 09/19] PCI/TSM: Support creating encrypted MMIO descriptors via TDISP Report

[<dan.j.williams@intel.com>]

Dan Williams wrote:
> After pci_tsm_bind() and pci_tsm_lock() the low level TSM driver is
> expected to populate PCI_TSM_EVIDENCE_TYPE_REPORT in its evidence store.
> This report is defined by the TDISP GET_DEVICE_INTERFACE_REPORT response
> payload.
> 
> Add a helper to create encrypted MMIO descriptors from that report
> data. With those descriptors the TSM driver can use pci_tsm_mmio_setup() to
> inform ioremap() how to map the device per the device's expectations. The
> VM is expected to validate the interface with the relying party before
> accepting the device for operation.
> 
> The helper also provides the obfuscated starting address for each
> encrypted MMIO range as the VM is never disclosed on the hpa that
> correlates to the gpa of the device's mmio. The obfuscated address is BAR
> relative.
> 
> Based on an original patch by Aneesh [1]
> 
> Cc: Arnd Bergmann <arnd@arndb.de>
> Link: https://lore.kernel.org/linux-coco/20251117140007.122062-8-aneesh.kumar@kernel.org/
> Co-developed-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Xu Yilun <yilun.xu@linux.intel.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
[..]
> +/**
> + * pci_tsm_mmio_alloc() - allocate encrypted MMIO range descriptor
> + * @pdev: device owner of MMIO ranges
> + * @report_data: TDISP Device Interface (DevIf) Report blob
> + * @report_sz: DevIf Report size
> + *
> + * Return: the encrypted MMIO range descriptor on success, NULL on failure
> + *
> + * Assumes that this is called within the live lifetime of a PCI device's
> + * association with a low level TSM.
> + */
> +struct pci_tsm_mmio *pci_tsm_mmio_alloc(struct pci_dev *pdev)
> +{
> +	struct pci_tsm *tsm = pdev->tsm;
> +	struct pci_tsm_evidence *evidence = &tsm->evidence;
> +	struct pci_tsm_evidence_object *report_obj = &evidence->obj[PCI_TSM_EVIDENCE_TYPE_REPORT];
> +	struct tsm_dev *tsm_dev = tsm->tsm_dev;
> +	u64 reporting_bar_base, last_reporting_end;
> +	const struct pci_tsm_devif_report *report;
> +	u32 mmio_range_count;
> +	int last_bar = -1;
> +	int i;
> +
> +	guard(rwsem_read)(&evidence->lock);
> +	if (report_obj->len < sizeof(struct pci_tsm_devif_report))
> +		return NULL;
> +
> +	if (dev_WARN_ONCE(&tsm_dev->dev, !IS_ALIGNED((unsigned long) report_obj->data, 8),
> +			  "misaligned report data\n"))
> +		return NULL;

Is this going to cause any implementation to need to copy the buffer
received from the low-level TSM? If so I would just mark 'struct
pci_tsm_devif_report' and 'struct pci_tsm_mmio_entry' as __packed and
drop this check.

> +
> +	report = report_obj->data;
> +	mmio_range_count = __le32_to_cpu(report->mmio_range_count);
> +
> +	/* check that the report object is self-consistent on mmio entries */
> +	if (report_obj->len < struct_size(report, mmio, mmio_range_count))
> +		return NULL;
> +
> +	/* create pci_tsm_mmio descriptors from the report data */
> +	struct pci_tsm_mmio *mmio __free(kfree) =
> +		kzalloc(struct_size(mmio, mmio, mmio_range_count), GFP_KERNEL);
> +	if (!mmio)
> +		return NULL;
> +
> +	for (i = 0; i < mmio_range_count; i++) {
> +		u64 range_off;
> +		struct range range;
> +		const struct pci_tsm_devif_mmio *mmio_data = &report->mmio[i];
> +		struct pci_tsm_mmio_entry *entry =
> +			pci_tsm_mmio_entry(mmio, mmio->nr);
> +		/* report values in are in terms of 4K pages */
> +		u64 tsm_offset = __le64_to_cpu(mmio_data->pfn) * SZ_4K;
> +		u64 size = __le32_to_cpu(mmio_data->nr_pfns) * SZ_4K;
> +		u32 attr = __le32_to_cpu(mmio_data->attributes);
> +		int bar = FIELD_GET(PCI_TSM_DEVIF_REPORT_MMIO_ATTR_RANGE_ID,
> +				    attr);
> +
> +		tsm_offset *= SZ_4K;
> +		size *= SZ_4K;

Whoops, these pfn to absolute address conversions were already performed above, will fix.