[PATCH 15/19] KVM: PPC: Book3S HV: add get/set accessors for the source configuration

Thu Feb 7 13:48:55 AEDT 2019

On Wed, Feb 06, 2019 at 08:07:36AM +0100, Cédric Le Goater wrote:
> On 2/6/19 2:24 AM, David Gibson wrote:
> > On Wed, Feb 06, 2019 at 12:23:29PM +1100, David Gibson wrote:
> >> On Tue, Feb 05, 2019 at 02:03:11PM +0100, Cédric Le Goater wrote:
> >>> On 2/5/19 6:32 AM, David Gibson wrote:
> >>>> On Mon, Feb 04, 2019 at 05:07:28PM +0100, Cédric Le Goater wrote:
> >>>>> On 2/4/19 6:21 AM, David Gibson wrote:
> >>>>>> On Mon, Jan 07, 2019 at 07:43:27PM +0100, Cédric Le Goater wrote:
> >>>>>>> Theses are use to capure the XIVE EAS table of the KVM device, the
> >>>>>>> configuration of the source targets.
> >>>>>>>
> >>>>>>> Signed-off-by: Cédric Le Goater <clg at kaod.org>
> >>>>>>> ---
> >>>>>>>  arch/powerpc/include/uapi/asm/kvm.h   | 11 ++++
> >>>>>>>  arch/powerpc/kvm/book3s_xive_native.c | 87 +++++++++++++++++++++++++++
> >>>>>>>  2 files changed, 98 insertions(+)
> >>>>>>>
> >>>>>>> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> >>>>>>> index 1a8740629acf..faf024f39858 100644
> >>>>>>> --- a/arch/powerpc/include/uapi/asm/kvm.h
> >>>>>>> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> >>>>>>> @@ -683,9 +683,20 @@ struct kvm_ppc_cpu_char {
> >>>>>>>  #define   KVM_DEV_XIVE_SAVE_EQ_PAGES	4
> >>>>>>>  #define KVM_DEV_XIVE_GRP_SOURCES	2	/* 64-bit source attributes */
> >>>>>>>  #define KVM_DEV_XIVE_GRP_SYNC		3	/* 64-bit source attributes */
> >>>>>>> +#define KVM_DEV_XIVE_GRP_EAS		4	/* 64-bit eas attributes */
> >>>>>>>  
> >>>>>>>  /* Layout of 64-bit XIVE source attribute values */
> >>>>>>>  #define KVM_XIVE_LEVEL_SENSITIVE	(1ULL << 0)
> >>>>>>>  #define KVM_XIVE_LEVEL_ASSERTED		(1ULL << 1)
> >>>>>>>  
> >>>>>>> +/* Layout of 64-bit eas attribute values */
> >>>>>>> +#define KVM_XIVE_EAS_PRIORITY_SHIFT	0
> >>>>>>> +#define KVM_XIVE_EAS_PRIORITY_MASK	0x7
> >>>>>>> +#define KVM_XIVE_EAS_SERVER_SHIFT	3
> >>>>>>> +#define KVM_XIVE_EAS_SERVER_MASK	0xfffffff8ULL
> >>>>>>> +#define KVM_XIVE_EAS_MASK_SHIFT		32
> >>>>>>> +#define KVM_XIVE_EAS_MASK_MASK		0x100000000ULL
> >>>>>>> +#define KVM_XIVE_EAS_EISN_SHIFT		33
> >>>>>>> +#define KVM_XIVE_EAS_EISN_MASK		0xfffffffe00000000ULL
> >>>>>>> +
> >>>>>>>  #endif /* __LINUX_KVM_POWERPC_H */
> >>>>>>> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> >>>>>>> index f2de1bcf3b35..0468b605baa7 100644
> >>>>>>> --- a/arch/powerpc/kvm/book3s_xive_native.c
> >>>>>>> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> >>>>>>> @@ -525,6 +525,88 @@ static int kvmppc_xive_native_sync(struct kvmppc_xive *xive, long irq, u64 addr)
> >>>>>>>  	return 0;
> >>>>>>>  }
> >>>>>>>  
> >>>>>>> +static int kvmppc_xive_native_set_eas(struct kvmppc_xive *xive, long irq,
> >>>>>>> +				      u64 addr)
> >>>>>>
> >>>>>> I'd prefer to avoid the name "EAS" here.  IIUC these aren't "raw" EAS
> >>>>>> values, but rather essentially the "source config" in the terminology
> >>>>>> of the PAPR hcalls.  Which, yes, is basically implemented by setting
> >>>>>> the EAS, but since it's the PAPR architected state that we need to
> >>>>>> preserve across migration, I'd prefer to stick as close as we can to
> >>>>>> the PAPR terminology.
> >>>>>
> >>>>> But we don't have an equivalent name in the PAPR specs for the tuple 
> >>>>> (prio, server). We could use the generic 'target' name may be ? even 
> >>>>> if this is usually referring to a CPU number.
> >>>>
> >>>> Um.. what?  That's about terminology for one of the fields in this
> >>>> thing, not about the name for the thing itself.
> >>>>
> >>>>> Or, IVE (Interrupt Vector Entry) ? which makes some sense. 
> >>>>> This is was the former name in HW. I think we recycle it for KVM.
> >>>>
> >>>> That's a terrible idea, which will make a confusing situation even
> >>>> more confusing.
> >>>
> >>> Let's use SOURCE_CONFIG and QUEUE_CONFIG. The KVM ioctls are very 
> >>> similar to the hcalls anyhow.
> >>
> >> Yes, I think that's a good idea.
> > 
> > Actually... AIUI the SET_CONFIG hcalls shouldn't be a fast path.  
> 
> No indeed. I have move them to standard hcalls in the current version.
> 
> > Can
> > we simplify things further by removing the hcall implementation from
> > the kernel entirely, and have qemu implement them by basically just
> > forwarding them to the appropriate SET_CONFIG ioctl()?
> 
> Yes. I think we could. 

Great!

> The hcalls H_INT_SET_SOURCE_CONFIG and H_INT_SET_QUEUE_CONFIG and 
> the KVM ioctls to set the EQ and the SOURCE configuration have a 
> lot in common. I need to look at how we can plug the KVM ioctl in 
> the hcalls under QEMU.
> 
> We will have to convert the returned error to respect the PAPR 
> specs or have the ioctls return H_* errors.

I don't think returning H_* values from a kernel call is a good idea.
Converting errors is kinda ugly, but I still think it's the better
option.  Note that we already have something like this for the HPT
resizing hcalls.

> Let's dig that idea. If we choose that path, QEMU will have an 
> up-to-date EAT and so we won't need to synchronize its state anymore 
> for migration.

I guess so, though I don't see that as essential.

> H_INT_GET_SOURCE_CONFIG can be implemented in QEMU without any KVM 
> ioctl.
> 
> H_INT_GET_QUEUE_INFO could be implemented in QEMU. I need to check 
> how we return the address of the END ESB in sPAPR. We haven't paid 
> much attention to these pages because they are not used under Linux
> and today the address is returned by OPAL. 
> 
> H_INT_GET_QUEUE_CONFIG is a little more problematic because we need
> to query into the XIVE HW the EQ index and toggle bit. OPAL support
> is required for that. But we could reduce the KVM support to the 
> ioctl querying these EQ information.

Right, and we'd need an ioctl() like that for migration anyway, yes?

> H_INT_ESB could be entirely done under QEMU.

This one can actually happen on fairly hot paths, so I think doing
that in qemu probably isn't a good idea.

> H_INT_SYNC and H_INT_RESET can not.
> 
> H_INT_GET_OS_REPORTING_LINE and H_INT_SET_OS_REPORTING_LINE are not
> implemented.
> 
> C.
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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