[Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads

[Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads

[Kevin O'Connor]

Return a static signature ("QEMU CFG") if the guest does a read to the
DMA address io register.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---

Marc, if you decide to respin your fw_cfg series, I've updated the dma
signature patch.  This addresses the comments from Stefan, and I hope
it addresses the comments from Laszlo.

BTW, if you wanted to, it's possible to use deposit64 in
fw_cfg_dma_mem_write() to support all possible (validly aligned) write
sizes.  Then fw_cfg_dma_mem_valid() shouldn't be needed.  Something
like:

static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
                                 uint64_t value, unsigned size)
{
    FWCfgState *s = opaque;
    s->dma_addr = deposit64(s->dma_addr, (8 - addr - size)*8, size*8, value);
    if (addr + size >= 8) {
        fw_cfg_dma_transfer(s);
    }
}

---
 docs/specs/fw_cfg.txt |  3 +++
 hw/nvram/fw_cfg.c     | 14 ++++++++++++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
index 2d6b2da..cbdce7d 100644
--- a/docs/specs/fw_cfg.txt
+++ b/docs/specs/fw_cfg.txt
@@ -93,6 +93,9 @@ by selecting the "signature" item using key 0x0000 (FW_CFG_SIGNATURE),
 and reading four bytes from the data register. If the fw_cfg device is
 present, the four bytes read will contain the characters "QEMU".
 
+If the DMA interface is available, then reading the DMA Address
+Register returns 0x51454d5520434647 ("QEMU CFG" in big-endian format).
+
 === Revision / feature bitmap (Key 0x0001, FW_CFG_ID) ===
 
 A 32-bit little-endian unsigned int, this item is used to check for enabled
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 59933b3..cf5c5c4 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -53,6 +53,8 @@
 #define FW_CFG_DMA_CTL_SKIP    0x04
 #define FW_CFG_DMA_CTL_SELECT  0x08
 
+#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647 /* "QEMU CFG" */
+
 typedef struct FWCfgEntry {
     uint32_t len;
     uint8_t *data;
@@ -393,6 +395,13 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
     trace_fw_cfg_read(s, 0);
 }
 
+static uint64_t fw_cfg_dma_mem_read(void *opaque, hwaddr addr,
+                                    unsigned size)
+{
+    // Return a signature value (and handle various read sizes)
+    return extract64(FW_CFG_DMA_SIGNATURE, (8 - addr - size) * 8, size*8);
+}
+
 static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
                                  uint64_t value, unsigned size)
 {
@@ -416,8 +425,8 @@ static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
 static bool fw_cfg_dma_mem_valid(void *opaque, hwaddr addr,
                                   unsigned size, bool is_write)
 {
-    return is_write && ((size == 4 && (addr == 0 || addr == 4)) ||
-                        (size == 8 && addr == 0));
+    return !is_write || ((size == 4 && (addr == 0 || addr == 4)) ||
+                         (size == 8 && addr == 0));
 }
 
 static bool fw_cfg_data_mem_valid(void *opaque, hwaddr addr,
@@ -488,6 +497,7 @@ static const MemoryRegionOps fw_cfg_comb_mem_ops = {
 };
 
 static const MemoryRegionOps fw_cfg_dma_mem_ops = {
+    .read = fw_cfg_dma_mem_read,
     .write = fw_cfg_dma_mem_write,
     .endianness = DEVICE_BIG_ENDIAN,
     .valid.accepts = fw_cfg_dma_mem_valid,
-- 
2.4.3

Re: [Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads

[Laszlo Ersek]

On 10/06/15 01:51, Kevin O'Connor wrote:
> Return a static signature ("QEMU CFG") if the guest does a read to the
> DMA address io register.
> 
> Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
> ---
> 
> Marc, if you decide to respin your fw_cfg series, I've updated the dma
> signature patch.  This addresses the comments from Stefan, and I hope
> it addresses the comments from Laszlo.

Thank you -- I didn't know about extract64().

The patch looks good to me, but I think the QEMU coding style requries
/* ... */ comments, and forbids //.

... "scripts/checkpatch.pl" has the following snippet:

# no C99 // comments
                if ($line =~ m{//}) {
                        ERROR("do not use C99 // comments\n" . $herecurr);
                }
...

Thanks!
Laszlo

> 
> BTW, if you wanted to, it's possible to use deposit64 in
> fw_cfg_dma_mem_write() to support all possible (validly aligned) write
> sizes.  Then fw_cfg_dma_mem_valid() shouldn't be needed.  Something
> like:
> 
> static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
>                                  uint64_t value, unsigned size)
> {
>     FWCfgState *s = opaque;
>     s->dma_addr = deposit64(s->dma_addr, (8 - addr - size)*8, size*8, value);
>     if (addr + size >= 8) {
>         fw_cfg_dma_transfer(s);
>     }
> }
> 
> ---
>  docs/specs/fw_cfg.txt |  3 +++
>  hw/nvram/fw_cfg.c     | 14 ++++++++++++--
>  2 files changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
> index 2d6b2da..cbdce7d 100644
> --- a/docs/specs/fw_cfg.txt
> +++ b/docs/specs/fw_cfg.txt
> @@ -93,6 +93,9 @@ by selecting the "signature" item using key 0x0000 (FW_CFG_SIGNATURE),
>  and reading four bytes from the data register. If the fw_cfg device is
>  present, the four bytes read will contain the characters "QEMU".
>  
> +If the DMA interface is available, then reading the DMA Address
> +Register returns 0x51454d5520434647 ("QEMU CFG" in big-endian format).
> +
>  === Revision / feature bitmap (Key 0x0001, FW_CFG_ID) ===
>  
>  A 32-bit little-endian unsigned int, this item is used to check for enabled
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 59933b3..cf5c5c4 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -53,6 +53,8 @@
>  #define FW_CFG_DMA_CTL_SKIP    0x04
>  #define FW_CFG_DMA_CTL_SELECT  0x08
>  
> +#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647 /* "QEMU CFG" */
> +
>  typedef struct FWCfgEntry {
>      uint32_t len;
>      uint8_t *data;
> @@ -393,6 +395,13 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
>      trace_fw_cfg_read(s, 0);
>  }
>  
> +static uint64_t fw_cfg_dma_mem_read(void *opaque, hwaddr addr,
> +                                    unsigned size)
> +{
> +    // Return a signature value (and handle various read sizes)
> +    return extract64(FW_CFG_DMA_SIGNATURE, (8 - addr - size) * 8, size*8);
> +}
> +
>  static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
>                                   uint64_t value, unsigned size)
>  {
> @@ -416,8 +425,8 @@ static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
>  static bool fw_cfg_dma_mem_valid(void *opaque, hwaddr addr,
>                                    unsigned size, bool is_write)
>  {
> -    return is_write && ((size == 4 && (addr == 0 || addr == 4)) ||
> -                        (size == 8 && addr == 0));
> +    return !is_write || ((size == 4 && (addr == 0 || addr == 4)) ||
> +                         (size == 8 && addr == 0));
>  }
>  
>  static bool fw_cfg_data_mem_valid(void *opaque, hwaddr addr,
> @@ -488,6 +497,7 @@ static const MemoryRegionOps fw_cfg_comb_mem_ops = {
>  };
>  
>  static const MemoryRegionOps fw_cfg_dma_mem_ops = {
> +    .read = fw_cfg_dma_mem_read,
>      .write = fw_cfg_dma_mem_write,
>      .endianness = DEVICE_BIG_ENDIAN,
>      .valid.accepts = fw_cfg_dma_mem_valid,
> 

Re: [Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads

[Stefan Hajnoczi]

On Mon, Oct 05, 2015 at 07:51:55PM -0400, Kevin O'Connor wrote:
> +static uint64_t fw_cfg_dma_mem_read(void *opaque, hwaddr addr,
> +                                    unsigned size)
> +{
> +    // Return a signature value (and handle various read sizes)
> +    return extract64(FW_CFG_DMA_SIGNATURE, (8 - addr - size) * 8, size*8);

Perhaps the maintainer can s/size*8/size * 8/ when applying this patch.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

Re: [Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads

[Kevin O'Connor]

On Tue, Oct 06, 2015 at 09:30:18AM +0200, Laszlo Ersek wrote:
> On 10/06/15 01:51, Kevin O'Connor wrote:
> > Return a static signature ("QEMU CFG") if the guest does a read to the
> > DMA address io register.
> > 
> > Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
> > ---
> > 
> > Marc, if you decide to respin your fw_cfg series, I've updated the dma
> > signature patch.  This addresses the comments from Stefan, and I hope
> > it addresses the comments from Laszlo.
> 
> Thank you -- I didn't know about extract64().
> 
> The patch looks good to me, but I think the QEMU coding style requries
> /* ... */ comments, and forbids //.

I always forget about that one.  Marc, if you do respin the series I
updated the patch below.

-Kevin


commit 02a449ece95da00fa64a9c704555c6afa8e03579
Author: Kevin O'Connor <kevin@koconnor.net>
Date:   Thu Oct 1 14:16:59 2015 +0200

    fw_cfg: Define a static signature to be returned on DMA port reads
    
    Return a static signature ("QEMU CFG") if the guest does a read to the
    DMA address io register.
    
    Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
    Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
index 2d6b2da..cbdce7d 100644
--- a/docs/specs/fw_cfg.txt
+++ b/docs/specs/fw_cfg.txt
@@ -93,6 +93,9 @@ by selecting the "signature" item using key 0x0000 (FW_CFG_SIGNATURE),
 and reading four bytes from the data register. If the fw_cfg device is
 present, the four bytes read will contain the characters "QEMU".
 
+If the DMA interface is available, then reading the DMA Address
+Register returns 0x51454d5520434647 ("QEMU CFG" in big-endian format).
+
 === Revision / feature bitmap (Key 0x0001, FW_CFG_ID) ===
 
 A 32-bit little-endian unsigned int, this item is used to check for enabled
diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
index 59933b3..5098bfc 100644
--- a/hw/nvram/fw_cfg.c
+++ b/hw/nvram/fw_cfg.c
@@ -53,6 +53,8 @@
 #define FW_CFG_DMA_CTL_SKIP    0x04
 #define FW_CFG_DMA_CTL_SELECT  0x08
 
+#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647 /* "QEMU CFG" */
+
 typedef struct FWCfgEntry {
     uint32_t len;
     uint8_t *data;
@@ -393,6 +395,13 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
     trace_fw_cfg_read(s, 0);
 }
 
+static uint64_t fw_cfg_dma_mem_read(void *opaque, hwaddr addr,
+                                    unsigned size)
+{
+    /* Return a signature value (and handle various read sizes) */
+    return extract64(FW_CFG_DMA_SIGNATURE, (8 - addr - size) * 8, size * 8);
+}
+
 static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
                                  uint64_t value, unsigned size)
 {
@@ -416,8 +425,8 @@ static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
 static bool fw_cfg_dma_mem_valid(void *opaque, hwaddr addr,
                                   unsigned size, bool is_write)
 {
-    return is_write && ((size == 4 && (addr == 0 || addr == 4)) ||
-                        (size == 8 && addr == 0));
+    return !is_write || ((size == 4 && (addr == 0 || addr == 4)) ||
+                         (size == 8 && addr == 0));
 }
 
 static bool fw_cfg_data_mem_valid(void *opaque, hwaddr addr,
@@ -488,6 +497,7 @@ static const MemoryRegionOps fw_cfg_comb_mem_ops = {
 };
 
 static const MemoryRegionOps fw_cfg_dma_mem_ops = {
+    .read = fw_cfg_dma_mem_read,
     .write = fw_cfg_dma_mem_write,
     .endianness = DEVICE_BIG_ENDIAN,
     .valid.accepts = fw_cfg_dma_mem_valid,

Re: [Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads

[Laszlo Ersek]

On 10/06/15 16:29, Kevin O'Connor wrote:
> On Tue, Oct 06, 2015 at 09:30:18AM +0200, Laszlo Ersek wrote:
>> On 10/06/15 01:51, Kevin O'Connor wrote:
>>> Return a static signature ("QEMU CFG") if the guest does a read to the
>>> DMA address io register.
>>>
>>> Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
>>> ---
>>>
>>> Marc, if you decide to respin your fw_cfg series, I've updated the dma
>>> signature patch.  This addresses the comments from Stefan, and I hope
>>> it addresses the comments from Laszlo.
>>
>> Thank you -- I didn't know about extract64().
>>
>> The patch looks good to me, but I think the QEMU coding style requries
>> /* ... */ comments, and forbids //.
> 
> I always forget about that one.  Marc, if you do respin the series I
> updated the patch below.
> 
> -Kevin
> 
> 
> commit 02a449ece95da00fa64a9c704555c6afa8e03579
> Author: Kevin O'Connor <kevin@koconnor.net>
> Date:   Thu Oct 1 14:16:59 2015 +0200
> 
>     fw_cfg: Define a static signature to be returned on DMA port reads
>     
>     Return a static signature ("QEMU CFG") if the guest does a read to the
>     DMA address io register.
>     
>     Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>     Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
> 
> diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
> index 2d6b2da..cbdce7d 100644
> --- a/docs/specs/fw_cfg.txt
> +++ b/docs/specs/fw_cfg.txt
> @@ -93,6 +93,9 @@ by selecting the "signature" item using key 0x0000 (FW_CFG_SIGNATURE),
>  and reading four bytes from the data register. If the fw_cfg device is
>  present, the four bytes read will contain the characters "QEMU".
>  
> +If the DMA interface is available, then reading the DMA Address
> +Register returns 0x51454d5520434647 ("QEMU CFG" in big-endian format).
> +
>  === Revision / feature bitmap (Key 0x0001, FW_CFG_ID) ===
>  
>  A 32-bit little-endian unsigned int, this item is used to check for enabled
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 59933b3..5098bfc 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -53,6 +53,8 @@
>  #define FW_CFG_DMA_CTL_SKIP    0x04
>  #define FW_CFG_DMA_CTL_SELECT  0x08
>  
> +#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647 /* "QEMU CFG" */
> +
>  typedef struct FWCfgEntry {
>      uint32_t len;
>      uint8_t *data;
> @@ -393,6 +395,13 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
>      trace_fw_cfg_read(s, 0);
>  }
>  
> +static uint64_t fw_cfg_dma_mem_read(void *opaque, hwaddr addr,
> +                                    unsigned size)
> +{
> +    /* Return a signature value (and handle various read sizes) */
> +    return extract64(FW_CFG_DMA_SIGNATURE, (8 - addr - size) * 8, size * 8);
> +}
> +
>  static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
>                                   uint64_t value, unsigned size)
>  {
> @@ -416,8 +425,8 @@ static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
>  static bool fw_cfg_dma_mem_valid(void *opaque, hwaddr addr,
>                                    unsigned size, bool is_write)
>  {
> -    return is_write && ((size == 4 && (addr == 0 || addr == 4)) ||
> -                        (size == 8 && addr == 0));
> +    return !is_write || ((size == 4 && (addr == 0 || addr == 4)) ||
> +                         (size == 8 && addr == 0));
>  }
>  
>  static bool fw_cfg_data_mem_valid(void *opaque, hwaddr addr,
> @@ -488,6 +497,7 @@ static const MemoryRegionOps fw_cfg_comb_mem_ops = {
>  };
>  
>  static const MemoryRegionOps fw_cfg_dma_mem_ops = {
> +    .read = fw_cfg_dma_mem_read,
>      .write = fw_cfg_dma_mem_write,
>      .endianness = DEVICE_BIG_ENDIAN,
>      .valid.accepts = fw_cfg_dma_mem_valid,
> 

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

Thanks!
Laszlo

Re: [Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads

[Marc Marí]

On Tue, 6 Oct 2015 10:29:25 -0400
"Kevin O'Connor" <kevin@koconnor.net> wrote:

> On Tue, Oct 06, 2015 at 09:30:18AM +0200, Laszlo Ersek wrote:
> > On 10/06/15 01:51, Kevin O'Connor wrote:
> > > Return a static signature ("QEMU CFG") if the guest does a read
> > > to the DMA address io register.
> > > 
> > > Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
> > > ---
> > > 
> > > Marc, if you decide to respin your fw_cfg series, I've updated
> > > the dma signature patch.  This addresses the comments from
> > > Stefan, and I hope it addresses the comments from Laszlo.
> > 
> > Thank you -- I didn't know about extract64().
> > 
> > The patch looks good to me, but I think the QEMU coding style
> > requries /* ... */ comments, and forbids //.
> 
> I always forget about that one.  Marc, if you do respin the series I
> updated the patch below.
> 

This patch doesn't apply without the series. I'll add it to the series
and send it as soon as posible.

Thanks
Marc

> 
> 
> commit 02a449ece95da00fa64a9c704555c6afa8e03579
> Author: Kevin O'Connor <kevin@koconnor.net>
> Date:   Thu Oct 1 14:16:59 2015 +0200
> 
>     fw_cfg: Define a static signature to be returned on DMA port reads
>     
>     Return a static signature ("QEMU CFG") if the guest does a read
> to the DMA address io register.
>     
>     Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>     Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
> 
> diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
> index 2d6b2da..cbdce7d 100644
> --- a/docs/specs/fw_cfg.txt
> +++ b/docs/specs/fw_cfg.txt
> @@ -93,6 +93,9 @@ by selecting the "signature" item using key 0x0000
> (FW_CFG_SIGNATURE), and reading four bytes from the data register. If
> the fw_cfg device is present, the four bytes read will contain the
> characters "QEMU". 
> +If the DMA interface is available, then reading the DMA Address
> +Register returns 0x51454d5520434647 ("QEMU CFG" in big-endian
> format). +
>  === Revision / feature bitmap (Key 0x0001, FW_CFG_ID) ===
>  
>  A 32-bit little-endian unsigned int, this item is used to check for
> enabled diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 59933b3..5098bfc 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -53,6 +53,8 @@
>  #define FW_CFG_DMA_CTL_SKIP    0x04
>  #define FW_CFG_DMA_CTL_SELECT  0x08
>  
> +#define FW_CFG_DMA_SIGNATURE 0x51454d5520434647 /* "QEMU CFG" */
> +
>  typedef struct FWCfgEntry {
>      uint32_t len;
>      uint8_t *data;
> @@ -393,6 +395,13 @@ static void fw_cfg_dma_transfer(FWCfgState *s)
>      trace_fw_cfg_read(s, 0);
>  }
>  
> +static uint64_t fw_cfg_dma_mem_read(void *opaque, hwaddr addr,
> +                                    unsigned size)
> +{
> +    /* Return a signature value (and handle various read sizes) */
> +    return extract64(FW_CFG_DMA_SIGNATURE, (8 - addr - size) * 8,
> size * 8); +}
> +
>  static void fw_cfg_dma_mem_write(void *opaque, hwaddr addr,
>                                   uint64_t value, unsigned size)
>  {
> @@ -416,8 +425,8 @@ static void fw_cfg_dma_mem_write(void *opaque,
> hwaddr addr, static bool fw_cfg_dma_mem_valid(void *opaque, hwaddr
> addr, unsigned size, bool is_write)
>  {
> -    return is_write && ((size == 4 && (addr == 0 || addr == 4)) ||
> -                        (size == 8 && addr == 0));
> +    return !is_write || ((size == 4 && (addr == 0 || addr == 4)) ||
> +                         (size == 8 && addr == 0));
>  }
>  
>  static bool fw_cfg_data_mem_valid(void *opaque, hwaddr addr,
> @@ -488,6 +497,7 @@ static const MemoryRegionOps fw_cfg_comb_mem_ops
> = { };
>  
>  static const MemoryRegionOps fw_cfg_dma_mem_ops = {
> +    .read = fw_cfg_dma_mem_read,
>      .write = fw_cfg_dma_mem_write,
>      .endianness = DEVICE_BIG_ENDIAN,
>      .valid.accepts = fw_cfg_dma_mem_valid,
>