[Qemu-devel] [PATCH v2] bugfix: passing reference instead of value

[Qemu-devel] [PATCH v2] bugfix: passing reference instead of value

[Cao jin]

Fix the bug introduced by 595a4f07: Function host_pci_config_read() should be
passed by a reference, not a value, for the later pci_default_write_config().
And because value in PCI config space are little-endian, use cpu_to_le32() to
ensure it when write config.

Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
---
Separated from previous "igd-passthru convert to realize" patch. Since these
two don`t have dependency, can send it solely.

Not test since it is easy to find out if reading carefully, just compiled.

 hw/pci-host/piix.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index 715208b..a9cb983 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
     {0xa8, 4},  /* SNB: base of GTT stolen memory */
 };
 
-static int host_pci_config_read(int pos, int len, uint32_t val)
+static int host_pci_config_read(int pos, int len, uint32_t *val)
 {
     char path[PATH_MAX];
     int config_fd;
@@ -784,12 +784,14 @@ static int host_pci_config_read(int pos, int len, uint32_t val)
         ret = -errno;
         goto out;
     }
+
     do {
-        rc = read(config_fd, (uint8_t *)&val, len);
+        rc = read(config_fd, (uint8_t *)val, len);
     } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
     if (rc != len) {
         ret = -errno;
     }
+
 out:
     close(config_fd);
     return ret;
@@ -805,11 +807,11 @@ static int igd_pt_i440fx_initfn(struct PCIDevice *pci_dev)
     for (i = 0; i < num; i++) {
         pos = igd_host_bridge_infos[i].offset;
         len = igd_host_bridge_infos[i].len;
-        rc = host_pci_config_read(pos, len, val);
+        rc = host_pci_config_read(pos, len, &val);
         if (rc) {
             return -ENODEV;
         }
-        pci_default_write_config(pci_dev, pos, val, len);
+        pci_default_write_config(pci_dev, pos, cpu_to_le32(val), len);
     }
 
     return 0;
-- 
2.1.0

Re: [Qemu-devel] [PATCH v2] bugfix: passing reference instead of value

[Cao jin]

CC the code author: Tiejun Chen <tiejun.chen@intel.com>

On 12/28/2015 12:42 PM, Cao jin wrote:
> Fix the bug introduced by 595a4f07: Function host_pci_config_read() should be
> passed by a reference, not a value, for the later pci_default_write_config().
> And because value in PCI config space are little-endian, use cpu_to_le32() to
> ensure it when write config.
>
> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
> ---
> Separated from previous "igd-passthru convert to realize" patch. Since these
> two don`t have dependency, can send it solely.
>
> Not test since it is easy to find out if reading carefully, just compiled.
>
>   hw/pci-host/piix.c | 10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
> index 715208b..a9cb983 100644
> --- a/hw/pci-host/piix.c
> +++ b/hw/pci-host/piix.c
> @@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
>       {0xa8, 4},  /* SNB: base of GTT stolen memory */
>   };
>
> -static int host_pci_config_read(int pos, int len, uint32_t val)
> +static int host_pci_config_read(int pos, int len, uint32_t *val)
>   {
>       char path[PATH_MAX];
>       int config_fd;
> @@ -784,12 +784,14 @@ static int host_pci_config_read(int pos, int len, uint32_t val)
>           ret = -errno;
>           goto out;
>       }
> +
>       do {
> -        rc = read(config_fd, (uint8_t *)&val, len);
> +        rc = read(config_fd, (uint8_t *)val, len);
>       } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
>       if (rc != len) {
>           ret = -errno;
>       }
> +
>   out:
>       close(config_fd);
>       return ret;
> @@ -805,11 +807,11 @@ static int igd_pt_i440fx_initfn(struct PCIDevice *pci_dev)
>       for (i = 0; i < num; i++) {
>           pos = igd_host_bridge_infos[i].offset;
>           len = igd_host_bridge_infos[i].len;
> -        rc = host_pci_config_read(pos, len, val);
> +        rc = host_pci_config_read(pos, len, &val);
>           if (rc) {
>               return -ENODEV;
>           }
> -        pci_default_write_config(pci_dev, pos, val, len);
> +        pci_default_write_config(pci_dev, pos, cpu_to_le32(val), len);
>       }
>
>       return 0;
>

-- 
Yours Sincerely,

Cao Jin

Re: [Qemu-devel] [PATCH v2] bugfix: passing reference instead of value

[Cao jin]

Oops, got following feedback 2nd time:

The following message to <tiejun.chen@intel.com> was undeliverable.
The reason for the problem:
5.1.0 - Unknown address error 550-'#5.1.0 Address rejected.'

I guess the author address is not available anymore

On 12/29/2015 07:54 PM, Cao jin wrote:
> CC the code author: Tiejun Chen <tiejun.chen@intel.com>
>
> On 12/28/2015 12:42 PM, Cao jin wrote:
>> Fix the bug introduced by 595a4f07: Function host_pci_config_read()
>> should be
>> passed by a reference, not a value, for the later
>> pci_default_write_config().
>> And because value in PCI config space are little-endian, use
>> cpu_to_le32() to
>> ensure it when write config.
>>
>> Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
>> ---
>> Separated from previous "igd-passthru convert to realize" patch. Since
>> these
>> two don`t have dependency, can send it solely.
>>
>> Not test since it is easy to find out if reading carefully, just
>> compiled.
>>
>>   hw/pci-host/piix.c | 10 ++++++----
>>   1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
>> index 715208b..a9cb983 100644
>> --- a/hw/pci-host/piix.c
>> +++ b/hw/pci-host/piix.c
>> @@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
>>       {0xa8, 4},  /* SNB: base of GTT stolen memory */
>>   };
>>
>> -static int host_pci_config_read(int pos, int len, uint32_t val)
>> +static int host_pci_config_read(int pos, int len, uint32_t *val)
>>   {
>>       char path[PATH_MAX];
>>       int config_fd;
>> @@ -784,12 +784,14 @@ static int host_pci_config_read(int pos, int
>> len, uint32_t val)
>>           ret = -errno;
>>           goto out;
>>       }
>> +
>>       do {
>> -        rc = read(config_fd, (uint8_t *)&val, len);
>> +        rc = read(config_fd, (uint8_t *)val, len);
>>       } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
>>       if (rc != len) {
>>           ret = -errno;
>>       }
>> +
>>   out:
>>       close(config_fd);
>>       return ret;
>> @@ -805,11 +807,11 @@ static int igd_pt_i440fx_initfn(struct PCIDevice
>> *pci_dev)
>>       for (i = 0; i < num; i++) {
>>           pos = igd_host_bridge_infos[i].offset;
>>           len = igd_host_bridge_infos[i].len;
>> -        rc = host_pci_config_read(pos, len, val);
>> +        rc = host_pci_config_read(pos, len, &val);
>>           if (rc) {
>>               return -ENODEV;
>>           }
>> -        pci_default_write_config(pci_dev, pos, val, len);
>> +        pci_default_write_config(pci_dev, pos, cpu_to_le32(val), len);
>>       }
>>
>>       return 0;
>>
>

-- 
Yours Sincerely,

Cao Jin

Re: [Qemu-devel] [PATCH v2] bugfix: passing reference instead of value

[Paolo Bonzini]

>>> Separated from previous "igd-passthru convert to realize" patch. Since
>>> these two don`t have dependency, can send it solely.
>>>
>>> Not test since it is easy to find out if reading carefully, just
>>> compiled.

This patch works but the added conversion to LE is conceptually wrong.
The conversion from LE to CPU and vice versa is already done by
host_pci_config_read and pci_default_write_config.  You don't have it in
host_pci_config_read because the code is not portable and x86 is
little-endian.

Generally, functions that accept/return integers take care themselves of
endianness conversions.

Paolo


>>>   hw/pci-host/piix.c | 10 ++++++----
>>>   1 file changed, 6 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
>>> index 715208b..a9cb983 100644
>>> --- a/hw/pci-host/piix.c
>>> +++ b/hw/pci-host/piix.c
>>> @@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
>>>       {0xa8, 4},  /* SNB: base of GTT stolen memory */
>>>   };
>>>
>>> -static int host_pci_config_read(int pos, int len, uint32_t val)
>>> +static int host_pci_config_read(int pos, int len, uint32_t *val)
>>>   {
>>>       char path[PATH_MAX];
>>>       int config_fd;
>>> @@ -784,12 +784,14 @@ static int host_pci_config_read(int pos, int
>>> len, uint32_t val)
>>>           ret = -errno;
>>>           goto out;
>>>       }
>>> +
>>>       do {
>>> -        rc = read(config_fd, (uint8_t *)&val, len);
>>> +        rc = read(config_fd, (uint8_t *)val, len);
>>>       } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
>>>       if (rc != len) {
>>>           ret = -errno;
>>>       }
>>> +
>>>   out:
>>>       close(config_fd);
>>>       return ret;
>>> @@ -805,11 +807,11 @@ static int igd_pt_i440fx_initfn(struct PCIDevice
>>> *pci_dev)
>>>       for (i = 0; i < num; i++) {
>>>           pos = igd_host_bridge_infos[i].offset;
>>>           len = igd_host_bridge_infos[i].len;
>>> -        rc = host_pci_config_read(pos, len, val);
>>> +        rc = host_pci_config_read(pos, len, &val);
>>>           if (rc) {
>>>               return -ENODEV;
>>>           }
>>> -        pci_default_write_config(pci_dev, pos, val, len);
>>> +        pci_default_write_config(pci_dev, pos, cpu_to_le32(val), len);
>>>       }
>>>
>>>       return 0;
>>>
>>
> 

Re: [Qemu-devel] [PATCH v2] bugfix: passing reference instead of value

[Cao jin]

Hi Paolo

On 12/30/2015 12:25 AM, Paolo Bonzini wrote:
>>>> Separated from previous "igd-passthru convert to realize" patch. Since
>>>> these two don`t have dependency, can send it solely.
>>>>
>>>> Not test since it is easy to find out if reading carefully, just
>>>> compiled.
>
> This patch works but the added conversion to LE is conceptually wrong.
> The conversion from LE to CPU and vice versa is already done by
> host_pci_config_read and pci_default_write_config.  You don't have it in
> host_pci_config_read because the code is not portable and x86 is
> little-endian.
>

Do you mean, this code section(or this igd passthru device)will only run 
on x86? If it is, yes, the cpu_to_le32() is not necessary. If it has 
opportunity to run on BE, I think it is necessary, right?

The reason I add the conversion is that I am not sure whether it will 
run on a BE machine or not, and it will no bad to LE machine like x86.

> Generally, functions that accept/return integers take care themselves of
> endianness conversions.
>
> Paolo
>
>
>>>>    hw/pci-host/piix.c | 10 ++++++----
>>>>    1 file changed, 6 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
>>>> index 715208b..a9cb983 100644
>>>> --- a/hw/pci-host/piix.c
>>>> +++ b/hw/pci-host/piix.c
>>>> @@ -761,7 +761,7 @@ static const IGDHostInfo igd_host_bridge_infos[] = {
>>>>        {0xa8, 4},  /* SNB: base of GTT stolen memory */
>>>>    };
>>>>
>>>> -static int host_pci_config_read(int pos, int len, uint32_t val)
>>>> +static int host_pci_config_read(int pos, int len, uint32_t *val)
>>>>    {
>>>>        char path[PATH_MAX];
>>>>        int config_fd;
>>>> @@ -784,12 +784,14 @@ static int host_pci_config_read(int pos, int
>>>> len, uint32_t val)
>>>>            ret = -errno;
>>>>            goto out;
>>>>        }
>>>> +
>>>>        do {
>>>> -        rc = read(config_fd, (uint8_t *)&val, len);
>>>> +        rc = read(config_fd, (uint8_t *)val, len);
>>>>        } while (rc < 0 && (errno == EINTR || errno == EAGAIN));
>>>>        if (rc != len) {
>>>>            ret = -errno;
>>>>        }
>>>> +
>>>>    out:
>>>>        close(config_fd);
>>>>        return ret;
>>>> @@ -805,11 +807,11 @@ static int igd_pt_i440fx_initfn(struct PCIDevice
>>>> *pci_dev)
>>>>        for (i = 0; i < num; i++) {
>>>>            pos = igd_host_bridge_infos[i].offset;
>>>>            len = igd_host_bridge_infos[i].len;
>>>> -        rc = host_pci_config_read(pos, len, val);
>>>> +        rc = host_pci_config_read(pos, len, &val);
>>>>            if (rc) {
>>>>                return -ENODEV;
>>>>            }
>>>> -        pci_default_write_config(pci_dev, pos, val, len);
>>>> +        pci_default_write_config(pci_dev, pos, cpu_to_le32(val), len);
>>>>        }
>>>>
>>>>        return 0;
>>>>
>>>
>>
>
>
> .
>

-- 
Yours Sincerely,

Cao Jin