From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34826) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZuNFV-00027v-MB for qemu-devel@nongnu.org; Thu, 05 Nov 2015 11:18:57 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZuNFR-0001Rq-IX for qemu-devel@nongnu.org; Thu, 05 Nov 2015 11:18:53 -0500 Received: from mx1.redhat.com ([209.132.183.28]:40556) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZuNFR-0001Rk-BO for qemu-devel@nongnu.org; Thu, 05 Nov 2015 11:18:49 -0500 References: <1446733972-1602-1-git-send-email-somlo@cmu.edu> <1446733972-1602-6-git-send-email-somlo@cmu.edu> From: Laszlo Ersek Message-ID: <563B8164.9040609@redhat.com> Date: Thu, 5 Nov 2015 17:18:44 +0100 MIME-Version: 1.0 In-Reply-To: <1446733972-1602-6-git-send-email-somlo@cmu.edu> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v5 5/6] fw_cfg: add generic non-DMA read method List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Gabriel L. Somlo" , qemu-devel@nongnu.org Cc: peter.maydell@linaro.org, jordan.l.justen@intel.com, armbru@redhat.com, kraxel@redhat.com, pbonzini@redhat.com, markmb@redhat.com On 11/05/15 15:32, Gabriel L. Somlo wrote: > Introduce fw_cfg_data_read(), a generic read method which works > on all access widths (1 through 8 bytes, inclusive), and can be > used during both IOPort and MMIO read accesses. >=20 > To maintain legibility, only fw_cfg_data_mem_read() (the MMIO > data read method) is replaced by this patch. The new method > essentially unwinds the fw_cfg_data_mem_read() + fw_cfg_read() > combo, but without unnecessarily repeating all the validity > checks performed by the latter on each byte being read. >=20 > This patch also modifies the trace_fw_cfg_read prototype to > accept a 64-bit value argument, allowing it to work properly > with the new read method, but also remain backward compatible > with existing call sites. >=20 > Cc: Laszlo Ersek > Cc: Gerd Hoffmann > Cc: Marc Mar=C3=AD > Signed-off-by: Gabriel Somlo > --- >=20 > I think in this case I'll stick with a single assert for the > whole bounds check. In the long run, "easy to read" might be > just a bit more helpful than "in the VERY unlikely event of > actually triggering this, it will also tell us which side of > the interval we fell out on"... >=20 > Thanks again for all the advice and feedback! > --Gabriel >=20 > hw/nvram/fw_cfg.c | 45 +++++++++++++++++++++++++++++++-------------- > trace-events | 2 +- > 2 files changed, 32 insertions(+), 15 deletions(-) >=20 > diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c > index 046fa74..8f566f6 100644 > --- a/hw/nvram/fw_cfg.c > +++ b/hw/nvram/fw_cfg.c > @@ -274,6 +274,36 @@ static int fw_cfg_select(FWCfgState *s, uint16_t k= ey) > return ret; > } > =20 > +static uint64_t fw_cfg_data_read(void *opaque, hwaddr addr, unsigned s= ize) > +{ > + FWCfgState *s =3D opaque; > + int arch =3D !!(s->cur_entry & FW_CFG_ARCH_LOCAL); > + FWCfgEntry *e =3D (s->cur_entry =3D=3D FW_CFG_INVALID) ? NULL : > + &s->entries[arch][s->cur_entry & FW_CFG_ENTRY_MASK= ]; > + uint64_t value =3D 0; > + > + assert(size > 0 && size <=3D sizeof(value)); > + if (s->cur_entry !=3D FW_CFG_INVALID && e->data && s->cur_offset <= e->len) { > + /* The least significant 'size' bytes of the return value are > + * expected to contain a string preserving portion of the item > + * data, padded with zeros on the right in case we run out ear= ly. > + * In technical terms, we're composing the host-endian represe= ntation > + * of the big endian interpretation of the fw_cfg string. > + */ > + do { > + value =3D (value << 8) | e->data[s->cur_offset++]; > + } while (--size && s->cur_offset < e->len); > + /* If size is still not zero, we *did* run out early, so conti= nue > + * left-shifting, to add the appropriate number of padding zer= os > + * on the right. > + */ > + value <<=3D 8 * size; > + } > + > + trace_fw_cfg_read(s, value); > + return value; > +} > + > static uint8_t fw_cfg_read(FWCfgState *s) > { > int arch =3D !!(s->cur_entry & FW_CFG_ARCH_LOCAL); > @@ -291,19 +321,6 @@ static uint8_t fw_cfg_read(FWCfgState *s) > return ret; > } > =20 > -static uint64_t fw_cfg_data_mem_read(void *opaque, hwaddr addr, > - unsigned size) > -{ > - FWCfgState *s =3D opaque; > - uint64_t value =3D 0; > - unsigned i; > - > - for (i =3D 0; i < size; ++i) { > - value =3D (value << 8) | fw_cfg_read(s); > - } > - return value; > -} > - > static void fw_cfg_data_mem_write(void *opaque, hwaddr addr, > uint64_t value, unsigned size) > { > @@ -485,7 +502,7 @@ static const MemoryRegionOps fw_cfg_ctl_mem_ops =3D= { > }; > =20 > static const MemoryRegionOps fw_cfg_data_mem_ops =3D { > - .read =3D fw_cfg_data_mem_read, > + .read =3D fw_cfg_data_read, > .write =3D fw_cfg_data_mem_write, > .endianness =3D DEVICE_BIG_ENDIAN, > .valid =3D { > diff --git a/trace-events b/trace-events > index 17fbddf..f2f2ce4 100644 > --- a/trace-events > +++ b/trace-events > @@ -196,7 +196,7 @@ ecc_diag_mem_readb(uint64_t addr, uint32_t ret) "Re= ad diagnostic %"PRId64"=3D %02x > =20 > # hw/nvram/fw_cfg.c > fw_cfg_select(void *s, uint16_t key, int ret) "%p key %d =3D %d" > -fw_cfg_read(void *s, uint8_t ret) "%p =3D %d" > +fw_cfg_read(void *s, uint64_t ret) "%p =3D %"PRIx64 > fw_cfg_add_file(void *s, int index, char *name, size_t len) "%p #%d: %= s (%zd bytes)" > =20 > # hw/block/hd-geometry.c >=20 Reviewed-by: Laszlo Ersek