Re: [Qemu-devel] [PATCH v6 01/17] pci: fix unaligned access in pci_xxx_quad()

[Michael S. Tsirkin]

On Mon, May 30, 2016 at 06:05:57PM +0300, Dmitry Fleytman wrote:
> 
> > On 30 May 2016, at 17:47 PM, Michael S. Tsirkin <address@hidden> wrote:
> > 
> > On Mon, May 30, 2016 at 12:14:26PM +0300, Leonid Bloch wrote:
> >> From: Dmitry Fleytman <address@hidden>
> >> 
> >> Replace legacy cpu_to_le64w()/le64_to_cpup()
> >> calls with stq_le_p()/ldq_le_p().
> >> 
> >> Signed-off-by: Dmitry Fleytman <address@hidden>
> >> Signed-off-by: Leonid Bloch <address@hidden>
> > 
> 
> Hi Michael,
> 
> > Could you please add a code comment to clarify what's going on a bit more?
> > Something to the point that capabilities are guaranteed to
> > be dword-aligned only.
> > 
> 
> Just to clarify, do you want to add these comments to 
> pci_set/get_quad functions or to the new DSN-generation function?

pci_set/get_quad

> > Also, this isn't a dependency of this patchset I think -
> > as far as I could say the only user of this is
> >     pcie: Introduce function for DSN capability creation
> > but that merely accesses a capability, and all callers pass in
> > an aligned offset.
> 
> Right, this issue appeared after introduction of DSN generation function.

Does DSN generation function pass unaligned offsets?
It does not look like it does...

> All other callers pass aligned offsets so far.
> 
> Thanks,
> Dmitry
> 
> > 
> >> ---
> >> include/hw/pci/pci.h | 4 ++--
> >> 1 file changed, 2 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> >> index ef6ba51..ee238ad 100644
> >> --- a/include/hw/pci/pci.h
> >> +++ b/include/hw/pci/pci.h
> >> @@ -468,13 +468,13 @@ pci_get_long(const uint8_t *config)
> >> static inline void
> >> pci_set_quad(uint8_t *config, uint64_t val)
> >> {
> >> -    cpu_to_le64w((uint64_t *)config, val);
> >> +    stq_le_p(config, val);
> >> }
> >> 
> >> static inline uint64_t
> >> pci_get_quad(const uint8_t *config)
> >> {
> >> -    return le64_to_cpup((const uint64_t *)config);
> >> +    return ldq_le_p(config);
> >> }
> >> 
> >> static inline void
> >> -- 
> >> 2.5.5