Re: [Qemu-devel] [PATCH v2 1/3] KVM: Add new -cpu best

2012-07-02 Thread Alexander Graf

On 26.06.2012, at 18:39, Alexander Graf wrote:

 During discussions on whether to make -cpu host the default in SLE, I found
 myself disagreeing to the thought, because it potentially opens a big can
 of worms for potential bugs. But if I already am so opposed to it for SLE, how
 can it possibly be reasonable to default to -cpu host in upstream QEMU? And
 what would a sane default look like?
 
 So I had this idea of looping through all available CPU definitions. We can
 pretty well tell if our host is able to execute any of them by checking the
 respective flags and seeing if our host has all features the CPU definition
 requires. With that, we can create a -cpu type that would fall back to the
 best known CPU definition that our host can fulfill. On my Phenom II
 system for example, that would be -cpu phenom.
 
 With this approach we can test and verify that CPU types actually work at
 any random user setup, because we can always verify that all the -cpu types
 we ship actually work. And we only default to some clever mechanism that
 chooses from one of these.
 
 Signed-off-by: Alexander Graf ag...@suse.de

Ping :)


Alex

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Re: [Qemu-devel] [PATCH v2 1/3] KVM: Add new -cpu best

2012-07-02 Thread Andreas Färber
Am 26.06.2012 18:39, schrieb Alexander Graf:
 During discussions on whether to make -cpu host the default in SLE, I found

s/make -cpu host the default/support/?

 myself disagreeing to the thought, because it potentially opens a big can
 of worms for potential bugs. But if I already am so opposed to it for SLE, how
 can it possibly be reasonable to default to -cpu host in upstream QEMU? And
 what would a sane default look like?
 
 So I had this idea of looping through all available CPU definitions. We can
 pretty well tell if our host is able to execute any of them by checking the
 respective flags and seeing if our host has all features the CPU definition
 requires. With that, we can create a -cpu type that would fall back to the
 best known CPU definition that our host can fulfill. On my Phenom II
 system for example, that would be -cpu phenom.
 
 With this approach we can test and verify that CPU types actually work at
 any random user setup, because we can always verify that all the -cpu types
 we ship actually work. And we only default to some clever mechanism that
 chooses from one of these.
 
 Signed-off-by: Alexander Graf ag...@suse.de

Despite the long commit message a cover letter would've been nice. ;)

Anything that operates on x86_def_t will obviously need to be refactored
when we agree on the course for x86 CPU subclasses.
But no objection to getting it done some way that works today.

Andreas

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