linux-kernel - Re: [PATCH v2] PCI: endpoint: Skip odd BAR when skipping 64bit BAR

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Date:   Fri, 31 May 2019 10:05:45 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Alan Mikhak <alan.mikhak@...ive.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <lorenzo.pieralisi@....com>, <linux-riscv@...ts.infradead.org>,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        <gustavo.pimentel@...opsys.com>, <wen.yang99@....com.cn>,
        <kjlu@....edu>
Subject: Re: [PATCH v2] PCI: endpoint: Skip odd BAR when skipping 64bit BAR

Hi Alan,

On 25/05/19 12:20 AM, Alan Mikhak wrote:
> Hi Kishon,
> 
> Yes. This change is still applicable even when the platform specifies
> that it only supports 64-bit BARs by setting the bar_fixed_64bit
> member of epc_features.
> 
> The issue being fixed is this: If the 'continue' statement is executed
> within the loop, the loop index 'bar' needs to advanced by two, not
> one, when the BAR is 64-bit. Otherwise the next loop iteration will be
> on an odd BAR which doesn't exist.

IIUC you are fixing the case where the BAR is "reserved" (specified in
epc_features) and is also a 64-bit BAR?

If 2 consecutive BARs are marked as reserved in reserved_bar of epc_features,
the result should be the same right?

Thanks
Kishon

> 
> The PCI_BASE_ADDRESS_MEM_TYPE_64 flag in epf_bar->flag reflects the
> value set by the platform in the bar_fixed_64bit member of
> epc_features.
> 
> This patch moves the checking of  PCI_BASE_ADDRESS_MEM_TYPE_64 in
> epf_bar->flags to before the 'continue' statement to advance the 'bar'
> loop index accordingly. The comment you see about 'pci_epc_set_bar()'
> preceding the moved code is the original comment and was also moved
> along with the code.
> 
> Regards,
> Alan Mikhak
> 
> On Fri, May 24, 2019 at 1:51 AM Kishon Vijay Abraham I <kishon@...com> wrote:
>>
>> Hi,
>>
>> On 24/05/19 5:25 AM, Alan Mikhak wrote:
>>> +Bjorn Helgaas, +Gustavo Pimentel, +Wen Yang, +Kangjie Lu
>>>
>>> On Thu, May 23, 2019 at 2:55 PM Alan Mikhak <alan.mikhak@...ive.com> wrote:
>>>>
>>>> Always skip odd bar when skipping 64bit BARs in pci_epf_test_set_bar()
>>>> and pci_epf_test_alloc_space().
>>>>
>>>> Otherwise, pci_epf_test_set_bar() will call pci_epc_set_bar() on odd loop
>>>> index when skipping reserved 64bit BAR. Moreover, pci_epf_test_alloc_space()
>>>> will call pci_epf_alloc_space() on bind for odd loop index when BAR is 64bit
>>>> but leaks on subsequent unbind by not calling pci_epf_free_space().
>>>>
>>>> Signed-off-by: Alan Mikhak <alan.mikhak@...ive.com>
>>>> Reviewed-by: Paul Walmsley <paul.walmsley@...ive.com>
>>>> ---
>>>>  drivers/pci/endpoint/functions/pci-epf-test.c | 25 ++++++++++++-------------
>>>>  1 file changed, 12 insertions(+), 13 deletions(-)
>>>>
>>>> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
>>>> index 27806987e93b..96156a537922 100644
>>>> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
>>>> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
>>>> @@ -389,7 +389,7 @@ static void pci_epf_test_unbind(struct pci_epf *epf)
>>>>
>>>>  static int pci_epf_test_set_bar(struct pci_epf *epf)
>>>>  {
>>>> -       int bar;
>>>> +       int bar, add;
>>>>         int ret;
>>>>         struct pci_epf_bar *epf_bar;
>>>>         struct pci_epc *epc = epf->epc;
>>>> @@ -400,8 +400,14 @@ static int pci_epf_test_set_bar(struct pci_epf *epf)
>>>>
>>>>         epc_features = epf_test->epc_features;
>>>>
>>>> -       for (bar = BAR_0; bar <= BAR_5; bar++) {
>>>> +       for (bar = BAR_0; bar <= BAR_5; bar += add) {
>>>>                 epf_bar = &epf->bar[bar];
>>>> +               /*
>>>> +                * pci_epc_set_bar() sets PCI_BASE_ADDRESS_MEM_TYPE_64
>>>> +                * if the specific implementation required a 64-bit BAR,
>>>> +                * even if we only requested a 32-bit BAR.
>>>> +                */
>>
>> set_bar shouldn't set PCI_BASE_ADDRESS_MEM_TYPE_64. If a platform supports only
>> 64-bit BAR, that should be specified in epc_features bar_fixed_64bit member.
>>
>> Thanks
>> Kishon