[PATCH] wrong pa calculation fix (extboot)

[PATCH] wrong pa calculation fix (extboot)

[Nguyen Anh Quynh]

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This patch fixes a wrong calculation in the physical address of
extboot (qemu/hw/extboot.c). Looks like a typo.

Signed-off-by: Nguyen Anh Quynh <aquynh@gmail.com>

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diff --git a/qemu/hw/extboot.c b/qemu/hw/extboot.c
index 056fb59..0dac34c 100644
--- a/qemu/hw/extboot.c
+++ b/qemu/hw/extboot.c
@@ -81,7 +81,7 @@ static void extboot_write_cmd(void *opaque, uint32_t addr, uint32_t value)
     get_translated_chs(bs, &cylinders, &heads, &sectors);
 
     if (cmd->type == 0x01 || cmd->type == 0x02) {
-	target_ulong pa = cmd->xfer.segment * 16 + cmd->xfer.segment;
+	target_ulong pa = cmd->xfer.segment * 16 + cmd->xfer.offset;
 
 	/* possible buffer overflow */
 	if ((pa + cmd->xfer.nb_sectors * 512) > phys_ram_size)

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Re: [PATCH] wrong pa calculation fix (extboot)

[Anthony Liguori]

Nguyen Anh Quynh wrote:
> This patch fixes a wrong calculation in the physical address of
> extboot (qemu/hw/extboot.c). Looks like a typo.
>
> Signed-off-by: Nguyen Anh Quynh <aquynh@gmail.com>
>   
> diff --git a/qemu/hw/extboot.c b/qemu/hw/extboot.c
> index 056fb59..0dac34c 100644
> --- a/qemu/hw/extboot.c
> +++ b/qemu/hw/extboot.c
> @@ -81,7 +81,7 @@ static void extboot_write_cmd(void *opaque, uint32_t addr, uint32_t value)
>      get_translated_chs(bs, &cylinders, &heads, &sectors);
>  
>      if (cmd->type == 0x01 || cmd->type == 0x02) {
> -	target_ulong pa = cmd->xfer.segment * 16 + cmd->xfer.segment;
> +	target_ulong pa = cmd->xfer.segment * 16 + cmd->xfer.offset;
>  
>  	/* possible buffer overflow */
>  	if ((pa + cmd->xfer.nb_sectors * 512) > phys_ram_size)
>   

In practice, this check isn't actually necessary since a guest always 
has at least 1MB of memory.

Regards,

Anthony Liguori

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Re: [PATCH] wrong pa calculation fix (extboot)

[Nguyen Anh Quynh]

On 4/14/08, Anthony Liguori <aliguori@us.ibm.com> wrote:
> Nguyen Anh Quynh wrote:
>
> >
> > This patch fixes a wrong calculation in the physical address of
> > extboot (qemu/hw/extboot.c). Looks like a typo.
> >
> > Signed-off-by: Nguyen Anh Quynh <aquynh@gmail.com>
> >  diff --git a/qemu/hw/extboot.c b/qemu/hw/extboot.c
> > index 056fb59..0dac34c 100644
> > --- a/qemu/hw/extboot.c
> > +++ b/qemu/hw/extboot.c
> > @@ -81,7 +81,7 @@ static void extboot_write_cmd(void *opaque, uint32_t
> addr, uint32_t value)
> >     get_translated_chs(bs, &cylinders, &heads, &sectors);
> >       if (cmd->type == 0x01 || cmd->type == 0x02) {
> > -       target_ulong pa = cmd->xfer.segment * 16 + cmd->xfer.segment;
> > +       target_ulong pa = cmd->xfer.segment * 16 + cmd->xfer.offset;
> >          /* possible buffer overflow */
> >        if ((pa + cmd->xfer.nb_sectors * 512) > phys_ram_size)
> >
> >
>
>  In practice, this check isn't actually necessary since a guest always has
> at least 1MB of memory.

Agreed. But it needs to be fixed, anyway. Or we can remove it.

Thanks,
Q

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Re: [PATCH] wrong pa calculation fix (extboot)

[Anthony Liguori]

Nguyen Anh Quynh wrote:
> On 4/14/08, Anthony Liguori <aliguori@us.ibm.com> wrote:
>   
>> Nguyen Anh Quynh wrote:
>>     
>>
>>  In practice, this check isn't actually necessary since a guest always has
>> at least 1MB of memory.
>>     
>
> Agreed. But it needs to be fixed, anyway. Or we can remove it.
>   

Please just remove the whole check.

Regards,

Anthony Liguori

> Thanks,
> Q
>   


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Re: [PATCH] wrong pa calculation fix (extboot)

[Anthony Liguori]

Nguyen Anh Quynh wrote:
> On 4/14/08, Anthony Liguori <aliguori@us.ibm.com> wrote:
>   
>>  In practice, this check isn't actually necessary since a guest always has
>> at least 1MB of memory.
>>     
>
> Agreed. But it needs to be fixed, anyway. Or we can remove it.
>   

I should mention, the reason for removing the check, is that what we 
really want to do is remove all references to phys_ram_base() and 
replace them with cpu_physical_memory_{read,write}().  That will enforce 
memory checking.

Regards,

Anthony Liguori

> Thanks,
> Q
>   


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