From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43620) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZjMhf-0004Be-4k for qemu-devel@nongnu.org; Tue, 06 Oct 2015 03:30:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZjMha-0000js-PK for qemu-devel@nongnu.org; Tue, 06 Oct 2015 03:30:27 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42711) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZjMha-0000iG-Im for qemu-devel@nongnu.org; Tue, 06 Oct 2015 03:30:22 -0400 References: <1444089115-28710-1-git-send-email-kevin@koconnor.net> From: Laszlo Ersek Message-ID: <5613788A.1070409@redhat.com> Date: Tue, 6 Oct 2015 09:30:18 +0200 MIME-Version: 1.0 In-Reply-To: <1444089115-28710-1-git-send-email-kevin@koconnor.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCHv2] fw_cfg: Define a static signature to be returned on DMA port reads List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin O'Connor , qemu-devel@nongnu.org, =?UTF-8?Q?Marc_Mar=c3=ad?= Cc: Stefan Hajnoczi 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 > --- > > 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, >