Gregory Haskins wrote:

quoted

quoted

+struct shm_signal_irq {
+    __u8                  enabled;
+    __u8                  pending;
+    __u8                  dirty;
+};
  
      

Some ABIs may choose to pad this, suggest explicit padding.
    

Yeah, good idea.  What is the official way to do this these days?  Are
GCC pragmas allowed?

  

I just add a __u8 pad[5] in such cases.

quoted

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+
+struct shm_signal;
+
+struct shm_signal_ops {
+    int      (*inject)(struct shm_signal *s);
+    void     (*fault)(struct shm_signal *s, const char *fmt, ...);
  
      

Eww.  Must we involve strings and printf formats?
    

This is still somewhat of a immature part of the design.  Its supposed
to be used so that by default, its a panic.  But on the host side, we
can do something like inject a machine-check.  That way malicious/broken
guests cannot (should not? ;) be able to take down the host.  Note today
I do not map this to anything other than the default panic, so this
needs some love.

But given the asynchronous nature of the fault, I want to be sure we
have decent accounting to avoid bug reports like "silent MCE kills the
guest" ;)  At least this way, we can log the fault string somewhere to
get a clue.
  

I see.

This raises a point I've been thinking of - the symmetrical nature of 
the API vs the assymetrical nature of guest/host or user/kernel 
interfaces.  This is most pronounced in ->inject(); in the host->guest 
direction this is async (host can continue processing while the guest is 
handling the interrupt), whereas in the guest->host direction it is 
synchronous (the guest is blocked while the host is processing the call, 
unless the host explicitly hands off work to a different thread).


-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.