On Sat, 2 Jan 2016, Michael S. Tsirkin wrote: > On Sat, Jan 02, 2016 at 04:02:20PM +0800, Cao jin wrote: > > Fix the bug introduced by 595a4f07: function host_pci_config_read() should > > be > > pass-by-reference, not value. > > > > Signed-off-by: Cao jin <caoj.f...@cn.fujitsu.com> > > --- > > v3 changelog: > > 1. Remove cpu_to_le32() since the code only runs on X86. > > It really should be le32_to_cpu and a separate patch, > but I think it's preferable to have it there > since people tend to copy code around. > > But in any case, before merging any patches in this function I'd like to > hear a response from someone explaining why is this function necessary > at all, since it provably never did anything useful.
If Tiejun's email address bounces, then we are unlikely to get a reply. I think that the pass-by-value bug was introduced in one of the rebase/resend versions, as the series is very old and originally looked very different. I would take the patch as is to fix the obvious bug. This is how the original code looks like: http://xenbits.xen.org/gitweb/?p=qemu-xen-traditional.git;a=blob_plain;f=hw/pt-graphics.c;hb=HEAD See the function named igd_pci_read. > > > > hw/pci-host/piix.c | 8 +++++--- > > 1 file changed, 5 insertions(+), 3 deletions(-) > > > > diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c > > index 715208b..924f0fa 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; > > @@ -805,7 +807,7 @@ 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; > > } > > -- > > 2.1.0 > > > > >
