linux-kernel - Re: [PATCH V10 02/14] xen/pvh: Extend vcpu_guest

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Date:	Fri, 13 Dec 2013 09:26:51 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	David Vrabel <david.vrabel@...rix.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	Konrad Rzeszutek Wilk <konrad@...nel.org>,
	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
	george.dunlap@...citrix.com, ian.jackson@...citrix.com,
	mukesh.rathor@...cle.com, tim@....org, jbeulich@...e.com,
	boris.ostrovsky@...cle.com
Subject: Re: [PATCH V10 02/14] xen/pvh: Extend vcpu_guest_context, p2m,
 event, and XenBus.

On Fri, Dec 13, 2013 at 10:56:24AM +0000, David Vrabel wrote:
> On 13/12/13 02:10, Konrad Rzeszutek Wilk wrote:
> > From: Mukesh Rathor <mukesh.rathor@...cle.com>
> > 
> > Make gdt_frames[]/gdt_ents into a union with {gdtaddr, gdtsz},
> > as PVH only needs to send down gdtaddr and gdtsz in the
> > vcpu_guest_context structure..
> > 
> > For interrupts, PVH uses native_irq_ops so we can skip most of the
> > PV ones. In the future we can support the pirq_eoi_map..
> > Also VCPU hotplug is currently not available for PVH.
> > 
> > For events (and IRQs) we follow what PVHVM does - so use callback
> > vector.  Lastly, for XenBus we use the same logic that is used in
> > the PVHVM case.
> [...]
> > --- a/arch/x86/include/asm/xen/interface.h
> > +++ b/arch/x86/include/asm/xen/interface.h
> > @@ -145,7 +145,16 @@ struct vcpu_guest_context {
> >      struct cpu_user_regs user_regs;         /* User-level CPU registers     */
> >      struct trap_info trap_ctxt[256];        /* Virtual IDT                  */
> >      unsigned long ldt_base, ldt_ents;       /* LDT (linear address, # ents) */
> > -    unsigned long gdt_frames[16], gdt_ents; /* GDT (machine frames, # ents) */
> > +    union {
> > +	struct {
> > +		/* PV: GDT (machine frames, # ents).*/
> > +		unsigned long gdt_frames[16], gdt_ents;
> > +	} pv;
> > +	struct {
> > +		/* PVH: GDTR addr and size */
> > +		unsigned long gdtaddr, gdtsz;
> > +	} pvh;
> > +    } u;
> 
> Doesn't match the hypervisor.

Right. Mukesh is going to post follow on patches to fix that.

> 
> > --- a/arch/x86/xen/p2m.c
> > +++ b/arch/x86/xen/p2m.c
> > @@ -800,8 +800,10 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
> >  	unsigned topidx, mididx, idx;
> >  
> >  	/* don't track P2M changes in autotranslate guests */
> > -	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap)))
> > +	if (unlikely(xen_feature(XENFEAT_auto_translated_physmap))) {
> > +		BUG_ON(pfn != mfn && mfn != INVALID_P2M_ENTRY);
> >  		return true;
> > +	}
> 
> Isn't this undoing a recent change that removed this BUG_ON()?

This one:
commit 2f558d40911c1b8f929b8a382833ae1da5df3293
Author: Stefano Stabellini <stefano.stabellini@...citrix.com>
Date:   Wed Oct 9 20:39:01 2013 +0000

    xen/x86: allow __set_phys_to_machine for autotranslate guests
    
    Allow __set_phys_to_machine to be called for autotranslate guests.
    It can be used to keep track of phys_to_machine changes, however we
    don't do anything with the information at the moment.
    
    Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>

I am not actually sure why the BUG_ON was removed in Stefano's patch.
Stefano?

> 
> David
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