diff mbox

[RFC,4/6] xen: Print and use errno where applicable.

Message ID 1435605913-23826-5-git-send-email-konrad.wilk@oracle.com
State New
Headers show

Commit Message

Konrad Rzeszutek Wilk June 29, 2015, 7:25 p.m. UTC 
In Xen 4.6 commit cd2f100f0f61b3f333d52d1737dd73f02daee592
"libxc: Fix do_memory_op to return negative value on errors"
made the libxc API less odd-ball: On errors, return value is
-1 and error code is in errno. On success the return value
is either 0 or an positive value.

Since we could be running with an old toolstack in which the
Exx value is in rc or the newer, we print both and return
the -EXX depending on rc == -1 condition.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 xen-hvm.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

Comments

Stefano Stabellini July 1, 2015, 1:01 p.m. UTC | #1 
On Mon, 29 Jun 2015, Konrad Rzeszutek Wilk wrote:
> In Xen 4.6 commit cd2f100f0f61b3f333d52d1737dd73f02daee592
> "libxc: Fix do_memory_op to return negative value on errors"
> made the libxc API less odd-ball: On errors, return value is
> -1 and error code is in errno. On success the return value
> is either 0 or an positive value.
> 
> Since we could be running with an old toolstack in which the
> Exx value is in rc or the newer, we print both and return
> the -EXX depending on rc == -1 condition.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  xen-hvm.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/xen-hvm.c b/xen-hvm.c
> index 0408462..a92bc14 100644
> --- a/xen-hvm.c
> +++ b/xen-hvm.c
> @@ -345,11 +345,12 @@ go_physmap:
>          unsigned long idx = pfn + i;
>          xen_pfn_t gpfn = start_gpfn + i;
>  
> +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
>          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
>          if (rc) {
>              DPRINTF("add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> -            return -rc;
> +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> +            return rc == -1 ? -errno : -rc;

Printing both rc and errno is the right thing to do, but I am not sure
changing return value depending on the libxc version is a good idea.
Maybe we should be consistent and always return rc?


>          }
>      }
>  
> @@ -422,11 +423,12 @@ static int xen_remove_from_physmap(XenIOState *state,
>          xen_pfn_t idx = start_addr + i;
>          xen_pfn_t gpfn = phys_offset + i;
>  
> +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
>          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
>          if (rc) {
>              fprintf(stderr, "add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> -            return -rc;
> +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> +            return rc == -1 ? -errno : -rc;
>          }
>      }
>  
> -- 
> 2.1.0
>
Konrad Rzeszutek Wilk July 1, 2015, 6:22 p.m. UTC | #2 
On Wed, Jul 01, 2015 at 02:01:07PM +0100, Stefano Stabellini wrote:
> On Mon, 29 Jun 2015, Konrad Rzeszutek Wilk wrote:
> > In Xen 4.6 commit cd2f100f0f61b3f333d52d1737dd73f02daee592
> > "libxc: Fix do_memory_op to return negative value on errors"
> > made the libxc API less odd-ball: On errors, return value is
> > -1 and error code is in errno. On success the return value
> > is either 0 or an positive value.
> > 
> > Since we could be running with an old toolstack in which the
> > Exx value is in rc or the newer, we print both and return
> > the -EXX depending on rc == -1 condition.
> > 
> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > ---
> >  xen-hvm.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/xen-hvm.c b/xen-hvm.c
> > index 0408462..a92bc14 100644
> > --- a/xen-hvm.c
> > +++ b/xen-hvm.c
> > @@ -345,11 +345,12 @@ go_physmap:
> >          unsigned long idx = pfn + i;
> >          xen_pfn_t gpfn = start_gpfn + i;
> >  
> > +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
> >          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
> >          if (rc) {
> >              DPRINTF("add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> > -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> > -            return -rc;
> > +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> > +            return rc == -1 ? -errno : -rc;
> 
> Printing both rc and errno is the right thing to do, but I am not sure
> changing return value depending on the libxc version is a good idea.
> Maybe we should be consistent and always return rc?

In Xen 4.5 and earlier this function would return -EINVAL (say rc=EINVAL).
With Xen 4.6 it would always return 1 on errors (rc is -1, and with --1 we get 1), while
the errno would have EINVAL.

To be consistent and have this function return an proper -Exx value we
need that check to use errno in case rc == -1.

I am uncomfortable with returning positive values as errors, which reminds me -
I need to update the commit to mention the return 1 issue.
> 
> 
> >          }
> >      }
> >  
> > @@ -422,11 +423,12 @@ static int xen_remove_from_physmap(XenIOState *state,
> >          xen_pfn_t idx = start_addr + i;
> >          xen_pfn_t gpfn = phys_offset + i;
> >  
> > +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
> >          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
> >          if (rc) {
> >              fprintf(stderr, "add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> > -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> > -            return -rc;
> > +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> > +            return rc == -1 ? -errno : -rc;
> >          }
> >      }
> >  
> > -- 
> > 2.1.0
> >
Stefano Stabellini July 2, 2015, 11 a.m. UTC | #3 
On Wed, 1 Jul 2015, Konrad Rzeszutek Wilk wrote:
> On Wed, Jul 01, 2015 at 02:01:07PM +0100, Stefano Stabellini wrote:
> > On Mon, 29 Jun 2015, Konrad Rzeszutek Wilk wrote:
> > > In Xen 4.6 commit cd2f100f0f61b3f333d52d1737dd73f02daee592
> > > "libxc: Fix do_memory_op to return negative value on errors"
> > > made the libxc API less odd-ball: On errors, return value is
> > > -1 and error code is in errno. On success the return value
> > > is either 0 or an positive value.
> > > 
> > > Since we could be running with an old toolstack in which the
> > > Exx value is in rc or the newer, we print both and return
> > > the -EXX depending on rc == -1 condition.
> > > 
> > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > > ---
> > >  xen-hvm.c | 10 ++++++----
> > >  1 file changed, 6 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/xen-hvm.c b/xen-hvm.c
> > > index 0408462..a92bc14 100644
> > > --- a/xen-hvm.c
> > > +++ b/xen-hvm.c
> > > @@ -345,11 +345,12 @@ go_physmap:
> > >          unsigned long idx = pfn + i;
> > >          xen_pfn_t gpfn = start_gpfn + i;
> > >  
> > > +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
> > >          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
> > >          if (rc) {
> > >              DPRINTF("add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> > > -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> > > -            return -rc;
> > > +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> > > +            return rc == -1 ? -errno : -rc;
> > 
> > Printing both rc and errno is the right thing to do, but I am not sure
> > changing return value depending on the libxc version is a good idea.
> > Maybe we should be consistent and always return rc?
> 
> In Xen 4.5 and earlier this function would return -EINVAL (say rc=EINVAL).
> With Xen 4.6 it would always return 1 on errors (rc is -1, and with --1 we get 1), while
> the errno would have EINVAL.
> 
> To be consistent and have this function return an proper -Exx value we
> need that check to use errno in case rc == -1.

Maybe the best thing to do is to introduce a versioned
xen_xc_domain_add_to_physmap to include/hw/xen/xen_common.h


> I am uncomfortable with returning positive values as errors, which reminds me -
> I need to update the commit to mention the return 1 issue.

Agreed


> > 
> > 
> > >          }
> > >      }
> > >  
> > > @@ -422,11 +423,12 @@ static int xen_remove_from_physmap(XenIOState *state,
> > >          xen_pfn_t idx = start_addr + i;
> > >          xen_pfn_t gpfn = phys_offset + i;
> > >  
> > > +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
> > >          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
> > >          if (rc) {
> > >              fprintf(stderr, "add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> > > -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> > > -            return -rc;
> > > +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> > > +            return rc == -1 ? -errno : -rc;
> > >          }
> > >      }
> > >  
> > > -- 
> > > 2.1.0
> > > 
>
Konrad Rzeszutek Wilk July 2, 2015, 2:13 p.m. UTC | #4 
On Thu, Jul 02, 2015 at 12:00:29PM +0100, Stefano Stabellini wrote:
> On Wed, 1 Jul 2015, Konrad Rzeszutek Wilk wrote:
> > On Wed, Jul 01, 2015 at 02:01:07PM +0100, Stefano Stabellini wrote:
> > > On Mon, 29 Jun 2015, Konrad Rzeszutek Wilk wrote:
> > > > In Xen 4.6 commit cd2f100f0f61b3f333d52d1737dd73f02daee592
> > > > "libxc: Fix do_memory_op to return negative value on errors"
> > > > made the libxc API less odd-ball: On errors, return value is
> > > > -1 and error code is in errno. On success the return value
> > > > is either 0 or an positive value.
> > > > 
> > > > Since we could be running with an old toolstack in which the
> > > > Exx value is in rc or the newer, we print both and return
> > > > the -EXX depending on rc == -1 condition.
> > > > 
> > > > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > > > ---
> > > >  xen-hvm.c | 10 ++++++----
> > > >  1 file changed, 6 insertions(+), 4 deletions(-)
> > > > 
> > > > diff --git a/xen-hvm.c b/xen-hvm.c
> > > > index 0408462..a92bc14 100644
> > > > --- a/xen-hvm.c
> > > > +++ b/xen-hvm.c
> > > > @@ -345,11 +345,12 @@ go_physmap:
> > > >          unsigned long idx = pfn + i;
> > > >          xen_pfn_t gpfn = start_gpfn + i;
> > > >  
> > > > +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
> > > >          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
> > > >          if (rc) {
> > > >              DPRINTF("add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> > > > -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> > > > -            return -rc;
> > > > +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> > > > +            return rc == -1 ? -errno : -rc;
> > > 
> > > Printing both rc and errno is the right thing to do, but I am not sure
> > > changing return value depending on the libxc version is a good idea.
> > > Maybe we should be consistent and always return rc?
> > 
> > In Xen 4.5 and earlier this function would return -EINVAL (say rc=EINVAL).
> > With Xen 4.6 it would always return 1 on errors (rc is -1, and with --1 we get 1), while
> > the errno would have EINVAL.
> > 
> > To be consistent and have this function return an proper -Exx value we
> > need that check to use errno in case rc == -1.
> 
> Maybe the best thing to do is to introduce a versioned
> xen_xc_domain_add_to_physmap to include/hw/xen/xen_common.h

Aah, hadn't seen that before. Yes will do that.
> 
> 
> > I am uncomfortable with returning positive values as errors, which reminds me -
> > I need to update the commit to mention the return 1 issue.
> 
> Agreed
> 
> 
> > > 
> > > 
> > > >          }
> > > >      }
> > > >  
> > > > @@ -422,11 +423,12 @@ static int xen_remove_from_physmap(XenIOState *state,
> > > >          xen_pfn_t idx = start_addr + i;
> > > >          xen_pfn_t gpfn = phys_offset + i;
> > > >  
> > > > +        /* In Xen 4.6 rc is -1 and errno contains the error value. */
> > > >          rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
> > > >          if (rc) {
> > > >              fprintf(stderr, "add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
> > > > -                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
> > > > -            return -rc;
> > > > +                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
> > > > +            return rc == -1 ? -errno : -rc;
> > > >          }
> > > >      }
> > > >  
> > > > -- 
> > > > 2.1.0
> > > > 
> >
diff mbox

Patch

diff --git a/xen-hvm.c b/xen-hvm.c
index 0408462..a92bc14 100644
--- a/xen-hvm.c
+++ b/xen-hvm.c
@@ -345,11 +345,12 @@  go_physmap:
         unsigned long idx = pfn + i;
         xen_pfn_t gpfn = start_gpfn + i;
 
+        /* In Xen 4.6 rc is -1 and errno contains the error value. */
         rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
         if (rc) {
             DPRINTF("add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
-                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
-            return -rc;
+                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
+            return rc == -1 ? -errno : -rc;
         }
     }
 
@@ -422,11 +423,12 @@  static int xen_remove_from_physmap(XenIOState *state,
         xen_pfn_t idx = start_addr + i;
         xen_pfn_t gpfn = phys_offset + i;
 
+        /* In Xen 4.6 rc is -1 and errno contains the error value. */
         rc = xc_domain_add_to_physmap(xen_xc, xen_domid, XENMAPSPACE_gmfn, idx, gpfn);
         if (rc) {
             fprintf(stderr, "add_to_physmap MFN %"PRI_xen_pfn" to PFN %"
-                    PRI_xen_pfn" failed: %d\n", idx, gpfn, rc);
-            return -rc;
+                    PRI_xen_pfn" failed: %d (errno: %d)\n", idx, gpfn, rc, errno);
+            return rc == -1 ? -errno : -rc;
         }
     }