Re: [PATCH v6 17/43] hw/cxl/device: Add a memory device (8.2.8.5)

[Jonathan Cameron]

On Fri, 11 Feb 2022 12:07:21 +0000
Jonathan Cameron <Jonathan.Cameron@huawei.com> wrote:

> From: Ben Widawsky <ben.widawsky@intel.com>
> 
> A CXL memory device (AKA Type 3) is a CXL component that contains some
> combination of volatile and persistent memory. It also implements the
> previously defined mailbox interface as well as the memory device
> firmware interface.
> 
> Although the memory device is configured like a normal PCIe device, the
> memory traffic is on an entirely separate bus conceptually (using the
> same physical wires as PCIe, but different protocol).
> 
> Once the CXL topology is fully configure and address decoders committed,
> the guest physical address for the memory device is part of a larger
> window which is owned by the platform.  The creation of these windows
> is later in this series.
> 
> The following example will create a 256M device in a 512M window:
> -object "memory-backend-file,id=cxl-mem1,share,mem-path=cxl-type3,size=512M"
> -device "cxl-type3,bus=rp0,memdev=cxl-mem1,id=cxl-pmem0"
> 
> Note: Dropped PCDIMM info interfaces for now.  They can be added if
> appropriate at a later date.
> 
> Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

...

> +
> +static void cxl_setup_memory(CXLType3Dev *ct3d, Error **errp)
> +{
> +    MemoryRegion *mr;
> +
> +    if (!ct3d->hostmem) {
> +        error_setg(errp, "memdev property must be set");
> +        return;
> +    }
> +
> +    mr = host_memory_backend_get_memory(ct3d->hostmem);
> +    if (!mr) {
> +        error_setg(errp, "memdev property must be set");
> +        return;
> +    }
> +    memory_region_set_nonvolatile(mr, true);
> +    memory_region_set_enabled(mr, true);
> +    host_memory_backend_set_mapped(ct3d->hostmem, true);
> +    ct3d->cxl_dstate.pmem_size = ct3d->hostmem->size;
> +}
> +
> +
> +static void ct3_realize(PCIDevice *pci_dev, Error **errp)
> +{
> +    CXLType3Dev *ct3d = CT3(pci_dev);
> +    CXLComponentState *cxl_cstate = &ct3d->cxl_cstate;
> +    ComponentRegisters *regs = &cxl_cstate->crb;
> +    MemoryRegion *mr = &regs->component_registers;
> +    uint8_t *pci_conf = pci_dev->config;
> +
> +    if (!ct3d->hostmem) {

Ben pointed out in reply to v5 that this is backwards.
I'll fix in v7.  Clearly some of the cxl_setup_memory()
logic may also not be needed seeing as it wasn't running.


> +        cxl_setup_memory(ct3d, errp);
> +    }
> +
> +    pci_config_set_prog_interface(pci_conf, 0x10);
> +    pci_config_set_class(pci_conf, PCI_CLASS_MEMORY_CXL);
> +