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Date: Fri, 9 Sep 2022 14:19:11 +0200 From: Robert Richter <rrichter@....com> To: Dan Williams <dan.j.williams@...el.com> CC: Alison Schofield <alison.schofield@...el.com>, Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Ben Widawsky <bwidawsk@...nel.org>, <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, "Rafael J. Wysocki" <rafael@...nel.org>, Len Brown <lenb@...nel.org> Subject: Re: [PATCH 02/15] cxl/core: Check physical address before mapping it in devm_cxl_iomap_block() On 07.09.22 22:48:57, Dan Williams wrote: > Robert Richter wrote: > > The physical base address of a CXL range can be invalid and is then > > set to CXL_RESOURCE_NONE. Early check this case before mapping a > > memory block in devm_cxl_iomap_block(). > > > > Signed-off-by: Robert Richter <rrichter@....com> > > --- > > drivers/cxl/core/regs.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/cxl/core/regs.c b/drivers/cxl/core/regs.c > > index 39a129c57d40..f216c017a474 100644 > > --- a/drivers/cxl/core/regs.c > > +++ b/drivers/cxl/core/regs.c > > @@ -165,6 +165,9 @@ void __iomem *devm_cxl_iomap_block(struct device *dev, resource_size_t addr, > > void __iomem *ret_val; > > struct resource *res; > > > > + if (addr == CXL_RESOURCE_NONE) > > + return NULL; > > + > > res = devm_request_mem_region(dev, addr, length, dev_name(dev)); > > if (!res) { > > resource_size_t end = addr + length - 1; > > -- > > 2.30.2 > > > > devm_request_mem_region() succeeds for you when this happens? More > details about the failure scenario please. No, CXL_RESOURCE_NONE (all FFs) is used as address. A broken range is calculated that even overflows. I only vaguely remember the exact error message. This may happen e.g. if the Component Register Block is missing in the DVSEC. cxl_find_regblock() may fail then and returns CXL_RESOURCE_NONE. There are a couple of code paths there component_reg_phys is set to CXL_RESOURCE_NONE without exiting immediately. I saw it during code development, when I pre-inititalized a port with component_reg_phys set to CXL_RESOURCE_NONE. Since that case can generally happen, I think it must be checked. -Robert
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