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Violators will be prosecuted for from ; Fri, 1 Jul 2016 16:53:19 +1000 Subject: Re: [PATCH v3 4/7] PCI: Add a new option for resource_alignment to reassign alignment To: Gavin Shan References: <1467283993-3185-1-git-send-email-xyjxie@linux.vnet.ibm.com> <1467283993-3185-5-git-send-email-xyjxie@linux.vnet.ibm.com> <20160701022503.GA6739@gwshan> Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org, bhelgaas@google.com, alex.williamson@redhat.com, aik@ozlabs.ru, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, corbet@lwn.net, warrier@linux.vnet.ibm.com, zhong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com From: Yongji Xie Date: Fri, 1 Jul 2016 14:53:16 +0800 MIME-Version: 1.0 In-Reply-To: <20160701022503.GA6739@gwshan> Content-Type: text/plain; charset=utf-8; format=flowed Message-Id: <83859fc2-1c49-0f13-e91d-f0f5e3da7c5e@linux.vnet.ibm.com> Sender: linux-pci-owner@vger.kernel.org List-ID: Hi Gavin, On 2016/7/1 10:25, Gavin Shan wrote: > On Thu, Jun 30, 2016 at 06:53:10PM +0800, Yongji Xie wrote: >> When using resource_alignment kernel parameter, the current >> implement reassigns the alignment by changing resources' size >> which can potentially break some drivers. For example, the driver >> uses the size to locate some register whose length is related >> to the size. >> >> This patch adds a new option "noresize" for the parameter to >> solve this problem. >> >> Signed-off-by: Yongji Xie > Reviewed-by: Gavin Shan > >> --- >> Documentation/kernel-parameters.txt | 5 ++++- >> drivers/pci/pci.c | 35 +++++++++++++++++++++++++---------- >> 2 files changed, 29 insertions(+), 11 deletions(-) >> >> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt >> index 82b42c9..c4802f5 100644 >> --- a/Documentation/kernel-parameters.txt >> +++ b/Documentation/kernel-parameters.txt >> @@ -2997,13 +2997,16 @@ bytes respectively. Such letter suffixes can also be entirely omitted. >> window. The default value is 64 megabytes. >> resource_alignment= >> Format: >> - [@][:]:.[; ...] >> + [@][:]:. >> + [:noresize][; ...] >> Specifies alignment and device to reassign >> aligned memory resources. >> If is not specified, >> PAGE_SIZE is used as alignment. >> PCI-PCI bridge can be specified, if resource >> windows need to be expanded. >> + noresize: Don't change the resources' sizes when >> + reassigning alignment. >> ecrc= Enable/disable PCIe ECRC (transaction layer >> end-to-end CRC checking). >> bios: Use BIOS/firmware settings. This is the >> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >> index 6241cfc..1d80a94 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -4748,11 +4748,13 @@ static DEFINE_SPINLOCK(resource_alignment_lock); >> /** >> * pci_specified_resource_alignment - get resource alignment specified by user. >> * @dev: the PCI device to get >> + * @resize: whether or not to change resources' size when reassigning alignment >> * >> * RETURNS: Resource alignment if it is specified. >> * Zero if it is not specified. >> */ >> -static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev) >> +static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev, >> + bool *resize) >> { >> int seg, bus, slot, func, align_order, count; >> resource_size_t align = 0; >> @@ -4787,6 +4789,11 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev) >> } >> } >> p += count; >> + if (!strncmp(p, ":noresize", 9)) { >> + *resize = false; >> + p += 9; >> + } else >> + *resize = true; >> if (seg == pci_domain_nr(dev->bus) && >> bus == dev->bus->number && >> slot == PCI_SLOT(dev->devfn) && >> @@ -4819,6 +4826,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) >> { >> int i; >> struct resource *r; >> + bool resize = true; >> resource_size_t align, size; >> >> /* We should never try to reassign VF's alignment */ >> @@ -4826,7 +4834,7 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) >> return; >> >> /* check if specified PCI is target device to reassign */ >> - align = pci_specified_resource_alignment(dev); >> + align = pci_specified_resource_alignment(dev, &resize); >> if (!align) >> return; >> >> @@ -4848,15 +4856,22 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev) >> continue; >> } >> size = resource_size(r); >> - if (size < align) { >> - size = align; >> - dev_info(&dev->dev, >> - "Rounding up size of resource #%d to %#llx.\n", >> - i, (unsigned long long)size); >> + if (resize) { >> + if (size < align) { >> + size = align; >> + dev_info(&dev->dev, >> + "Rounding up size of resource #%d to %#llx.\n", >> + i, (unsigned long long)size); >> + } >> + r->flags |= IORESOURCE_UNSET; >> + r->end = size - 1; >> + r->start = 0; >> + } else { >> + r->flags &= ~IORESOURCE_SIZEALIGN; >> + r->flags |= IORESOURCE_STARTALIGN | IORESOURCE_UNSET; > f->flags |= (IORESOURCE_STARTALIGN | IORESOURCE_UNSET); > > Yongji, one quick question - when IORESOURCE_UNSET is cleared? If it's not > cleared, is there any unexpected side effects? Thanks. PCI core will clear this flag in pci_assign_resource() when the BAR has been assigned properly. If it's not cleared, the driver will fail in binding the device because pci_enable_resources() will check this flag. Thanks, Yongji