hw/9pfs: fix error handing in local_ioc_getversion()

v9fs_co_st_gen() expects to see error code in errno, not in return code.

Let's fix this.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
hw/9pfs: handle undefined FS_IOC_GETVERSION case in handle_ioc_getversion()

All get_st_gen() implementations except handle_ioc_getversion() have
guard for undefined FS_IOC_GETVERSION. Let's add it there too.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
hw/9pfs: make get_st_gen() return ENOTTY error on special files

Currently we silently ignore getversion requests for anything except
file or directory. Let's instead return ENOTTY error to indicate that
getversion is not supported. It makes implementation consistent on
all not-supported cases.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
hw/9pfs: fix P9_STATS_GEN handling

Currently we fail getattr request altogether if we can't read
P9_STATS_GEN for some reason. It breaks valid use cases:

E.g let's assume we have non-readable directory with execution bit set
on host and we export it to client over 9p On host we can chdir into
directory, but not open directory on read and list content.

But if client will try to call getattr (as part of chdir(2)) for the
directory it will fail with -EACCES. It happens because we try to open
the directory on read to call ioctl(FS_IOC_GETVERSION), it fails and we
return the error code to client.

It's excessive. The solution is to make P9_STATS_GEN failure non-fatal
for getattr request. Just don't set P9_STATS_GEN flag in result mask on
failure.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
memory: fix limiting of translation at a page boundary

Commit 360e607 (address_space_translate: do not cross page boundaries,
2014-01-30) broke MMIO accesses in cases where the section is shorter
than the full register width.  This can happen for example with the
Bochs DISPI registers, which are 16 bits wide but have only a 1-byte
long MemoryRegion (if you write to the "second byte" of the register
your access is discarded; it doesn't write only to half of the register).

Restrict the action of commit 360e607 to direct RAM accesses.  This
is enough for Xen, since MMIO will not go through the mapcache.

Reported-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Merge remote-tracking branch 'remotes/kvaneesh/for-upstream' into staging

* remotes/kvaneesh/for-upstream:
  hw/9pfs: fix P9_STATS_GEN handling
  hw/9pfs: make get_st_gen() return ENOTTY error on special files
  hw/9pfs: handle undefined FS_IOC_GETVERSION case in handle_ioc_getversion()
  hw/9pfs: fix error handing in local_ioc_getversion()

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>