Messages in this thread | | | Date | Tue, 15 Nov 2022 09:54:16 -0800 | From | Dan Williams <> | Subject | Re: [PATCH v3 2/9] cxl/acpi: Extract component registers of restricted hosts from RCRB |
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Robert Richter wrote: > On 14.11.22 13:30:01, Dan Williams wrote: > > Robert Richter wrote: > > > > diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c > > > index ec178e69b18f..7a5bde81e949 100644 > > > --- a/drivers/cxl/core/regs.c > > > +++ b/drivers/cxl/core/regs.c > > > @@ -307,3 +307,49 @@ int cxl_find_regblock(struct pci_dev *pdev, enum cxl_regloc_type type, > > > return -ENODEV; > > > } > > > EXPORT_SYMBOL_NS_GPL(cxl_find_regblock, CXL); > > > + > > > +resource_size_t cxl_rcrb_to_component(struct device *dev, > > > + resource_size_t rcrb, > > > + enum cxl_rcrb which) > > > +{ > > > + resource_size_t component_reg_phys; > > > + u32 bar0, bar1; > > > + void *addr; > > > + > > > + if (which == CXL_RCRB_UPSTREAM) > > > + rcrb += SZ_4K; > > > + > > > + /* > > > + * RCRB's BAR[0..1] point to component block containing CXL > > > + * subsystem component registers. MEMBAR extraction follows > > > + * the PCI Base spec here, esp. 64 bit extraction and memory > > > + * ranges alignment (6.0, 7.5.1.2.1). > > > + */ > > > > A request_mem_region() is needed here to ensure ownership and expected > > sequencing of accessing the RCRB to locate the component registers, and > > accessing the RCRB to manipulate the component registers. It also helps > > to sanity check that the BIOS mapped an exclusive range for the RCRB. > > Right, that is missing. > > > > > > + addr = ioremap(rcrb, PCI_BASE_ADDRESS_0 + SZ_8); > > > > That PCI_BASE_ADDRESS_0 does not belong there. It ends up being benign > > and forcing ioremap to map 12K instead of 8K, but it is a > > config-register offset, not part of the RCRB size. > > Note this is BAR0 + 8 bytes, not 8k, and it does not map the whole > RCRB region but instead the first part of the config space up to > including the 64 bit BAR.
Oh, sorry, yes, my mistake. However, there is not much value in mapping less than 4K since all ioremap requests are rounded up to PAGE_SIZE. Since an RCRB is only 4K per port lets just map the whole thing.
> > > + if (!addr) { > > > + dev_err(dev, "Failed to map region %pr\n", addr); > > > + return CXL_RESOURCE_NONE; > > > + } > > > + > > > + bar0 = readl(addr + PCI_BASE_ADDRESS_0); > > > + bar1 = readl(addr + PCI_BASE_ADDRESS_1); > > > + iounmap(addr); > > > > ...corresponding release_mem_region() would go here. > > > > > + > > > + /* sanity check */ > > > + if (bar0 & (PCI_BASE_ADDRESS_MEM_TYPE_1M | PCI_BASE_ADDRESS_SPACE_IO)) > > > + return CXL_RESOURCE_NONE; > > > > I would have also expected: > > > > - a sanity check for "Memory Space Enable" being set in the command > > register. > > Ok. > > > > > - an explicit check for 0xffffffff for the case when the upstream-port > > implements "no RCRB" mode. > > Yes, I left support for this to a later patch, but it's better to > check it here already and possibly fall back to reg loc DVSEC then.
Yeah, I think simply failing on 0xffffffff is sufficient for now.
> > > > - some check that BIOS initialized the BAR values post reset given these > > BARs are invisible to the PCI core resource assignment > > What check do you have in mind here? There is already the NULL check > which would be the out-of-reset value.
I was thinking more along the lines of sanity checking that the programmed RCRB range falls within the assigned MMIO space of the host-bridge, but perhaps that is overkill since it would just be validating self consistency between 2 BIOS provided values. Robustness principle would say try to continue if those disagree.
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