From: Hans Zhang <18255117159@163•com>
To: Keith Busch <kbusch@kernel•org>
Cc: "Gerd Bayer" <gbayer@linux•ibm.com>,
"Manivannan Sadhasivam" <mani@kernel•org>,
"Hans Zhang" <hans.zhang@cixtech•com>,
"Arnd Bergmann" <arnd@kernel•org>,
"Bjorn Helgaas" <helgaas@kernel•org>,
bhelgaas@google•com, "Alexander Gordeev" <agordeev@linux•ibm.com>,
"Christian Borntraeger" <borntraeger@linux•ibm.com>,
"Ilpo Järvinen" <ilpo.jarvinen@linux•intel.com>,
jingoohan1@gmail•com,
"Krzysztof Wilczy´nski" <kwilczynski@kernel•org>,
linux-kernel@vger•kernel.org, linux-s390@vger•kernel.org,
linux-next <linux-next@vger•kernel.org>,
linux-pci@vger•kernel.org,
"Lorenzo Pieralisi" <lpieralisi@kernel•org>,
"Rob Herring" <robh@kernel•org>,
"Niklas Schnelle" <schnelle@linux•ibm.com>,
geert@linux-m68k•org
Subject: Re: [PATCH] PCI: Fix endianness issues in pci_bus_read_config()
Date: Sat, 2 Aug 2025 23:23:34 +0800 [thread overview]
Message-ID: <d2240ab0-5d91-4b41-945f-e29b40f7b7f4@163.com> (raw)
In-Reply-To: <aI0CupiFvyOvgNQY@kbusch-mbp>
On 2025/8/2 02:08, Keith Busch wrote:
> On Sat, Aug 02, 2025 at 12:54:27AM +0800, Hans Zhang wrote:
>> As I mentioned in my reply to Mani's email, the data ultimately read here is
>> also a forced type conversion.
>>
>> #define PCI_OP_READ(size, type, len) \
>> int noinline pci_bus_read_config_##size \
>> (struct pci_bus *bus, unsigned int devfn, int pos, type *value) \
>> { \
>> unsigned long flags; \
>> u32 data = 0; \
>> int res; \
>> \
>> if (PCI_##size##_BAD) \
>> return PCIBIOS_BAD_REGISTER_NUMBER; \
>> \
>> pci_lock_config(flags); \
>> res = bus->ops->read(bus, devfn, pos, len, &data); \
>> if (res) \
>> PCI_SET_ERROR_RESPONSE(value); \
>> else \
>> *value = (type)data; \
>> pci_unlock_config(flags); \
>> \
>> return res; \
>> }
>>
>> And this function. Could it be that I misunderstood something?
>
> The above macro retains the caller's type for "value". If the caller
> passes a "u8 *", the value is deferenced as a u8.
Dear Keith,
In this macro definition, bus->ops->read needs to ensure the byte order
of the read, as Lukas mentioned; otherwise, there is also a big-endian
issue at this location.
>
> The function below promotes everything to a u32 pointer and deferences
> it as such regardless of what type the user passed in.
I searched and learned that readb/readw/readl automatically handle byte
order, so there is no big-endian order issue.
>
>> int pci_generic_config_read(struct pci_bus *bus, unsigned int devfn,
>> int where, int size, u32 *val)
>> {
>> void __iomem *addr;
>>
>> addr = bus->ops->map_bus(bus, devfn, where);
>> if (!addr)
>> return PCIBIOS_DEVICE_NOT_FOUND;
>>
>> if (size == 1)
>> *val = readb(addr);
>> else if (size == 2)
>> *val = readw(addr);
>> else
>> *val = readl(addr);
>>
>> return PCIBIOS_SUCCESSFUL;
>> }
Best regards,
Hans
next prev parent reply other threads:[~2025-08-02 15:24 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20250716231121.GA2564572@bhelgaas>
2025-07-31 7:32 ` [REGRESSION] next/master: suspect endianness issue in common PCI capability search macro Gerd Bayer
2025-07-31 17:38 ` [PATCH] PCI: Fix endianness issues in pci_bus_read_config() Gerd Bayer
2025-07-31 18:39 ` Bjorn Helgaas
2025-07-31 19:01 ` Arnd Bergmann
2025-08-01 8:18 ` Manivannan Sadhasivam
2025-08-01 9:25 ` Hans Zhang
2025-08-01 9:47 ` Manivannan Sadhasivam
2025-08-01 10:06 ` Hans Zhang
2025-08-01 10:54 ` Manivannan Sadhasivam
2025-08-01 11:30 ` Gerd Bayer
2025-08-01 16:54 ` Hans Zhang
2025-08-01 18:08 ` Keith Busch
2025-08-02 15:23 ` Hans Zhang [this message]
2025-08-02 15:40 ` Arnd Bergmann
2025-08-04 3:06 ` Hans Zhang
2025-08-04 8:03 ` Arnd Bergmann
2025-08-04 8:25 ` Hans Zhang
2025-08-04 10:09 ` Gerd Bayer
2025-08-12 14:44 ` Hans Zhang
2025-08-13 7:47 ` Niklas Schnelle
2025-08-13 7:50 ` Hans Zhang
2025-08-04 14:33 ` Bjorn Helgaas
2025-08-04 15:04 ` Hans Zhang
2025-08-01 16:47 ` Hans Zhang
2025-07-31 18:53 ` Lukas Wunner
2025-08-01 7:52 ` Geert Uytterhoeven
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