Re: [PATCH] KVM: PPC: Book3S PR: Set hflag to indicate that POWER9 supports 1T segments

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From: Paul Mackerras <paulus@ozlabs.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: aik@ozlabs.ru, linuxppc-dev@lists.ozlabs.org,
	kvm-ppc@vger.kernel.org,
	Suraj Jitindar Singh <sjitindarsingh@gmail.com>,
	kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: PPC: Book3S PR: Set hflag to indicate that POWER9 supports 1T segments
Date: Fri, 07 Dec 2018 11:42:12 +0000	[thread overview]
Message-ID: <20181207114212.GA23129@blackberry> (raw)
In-Reply-To: <871s6tlhln.fsf@concordia.ellerman.id.au>

On Fri, Dec 07, 2018 at 10:08:20PM +1100, Michael Ellerman wrote:
> Suraj Jitindar Singh <sjitindarsingh@gmail.com> writes:
> 
> > When booting a kvm-pr guest on a POWER9 machine the following message is
> > observed:
> > "qemu-system-ppc64: KVM does not support 1TiB segments which guest expects"
> >
> > This is because the guest is expecting to be able to use 1T segments
> > however we don't indicate support for it. This is because we don't set
> > the BOOK3S_HFLAG_MULTI_PGSIZE flag in the hflags in kvmppc_set_pvr_pr()
> > on POWER9.
> >
> > POWER9 does indeed have support for 1T segments, so add a case for
> > POWER9 to the switch statement to ensure it is set.
> 
> If this just checked mmu_has_feature(MMU_FTR_1T_SEGMENT) it would have
> been right in this case, and we'd also never have to update it in
> future.
> 
> Any reason not to?

PR KVM can emulate a different processor from the host.  Checking
mmu_has_feature() will tell you about the host, not the CPU being
emulated.

Paul.

WARNING: multiple messages have this Message-ID (diff)

From: Paul Mackerras <paulus@ozlabs.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: aik@ozlabs.ru, linuxppc-dev@lists.ozlabs.org,
	kvm-ppc@vger.kernel.org,
	Suraj Jitindar Singh <sjitindarsingh@gmail.com>,
	kvm@vger.kernel.org
Subject: Re: [PATCH] KVM: PPC: Book3S PR: Set hflag to indicate that POWER9 supports 1T segments
Date: Fri, 7 Dec 2018 22:42:12 +1100	[thread overview]
Message-ID: <20181207114212.GA23129@blackberry> (raw)
In-Reply-To: <871s6tlhln.fsf@concordia.ellerman.id.au>

On Fri, Dec 07, 2018 at 10:08:20PM +1100, Michael Ellerman wrote:
> Suraj Jitindar Singh <sjitindarsingh@gmail.com> writes:
> 
> > When booting a kvm-pr guest on a POWER9 machine the following message is
> > observed:
> > "qemu-system-ppc64: KVM does not support 1TiB segments which guest expects"
> >
> > This is because the guest is expecting to be able to use 1T segments
> > however we don't indicate support for it. This is because we don't set
> > the BOOK3S_HFLAG_MULTI_PGSIZE flag in the hflags in kvmppc_set_pvr_pr()
> > on POWER9.
> >
> > POWER9 does indeed have support for 1T segments, so add a case for
> > POWER9 to the switch statement to ensure it is set.
> 
> If this just checked mmu_has_feature(MMU_FTR_1T_SEGMENT) it would have
> been right in this case, and we'd also never have to update it in
> future.
> 
> Any reason not to?

PR KVM can emulate a different processor from the host.  Checking
mmu_has_feature() will tell you about the host, not the CPU being
emulated.

Paul.

next prev parent reply	other threads:[~2018-12-07 11:42 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-07  3:43 [PATCH 0/8] KVM: PPC: Implement passthrough of emulated devices for nested guests Suraj Jitindar Singh
2018-12-07  3:43 ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH] KVM: PPC: Book3S PR: Set hflag to indicate that POWER9 supports 1T segments Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07 11:08   ` Michael Ellerman
2018-12-07 11:08     ` Michael Ellerman
2018-12-07 11:42     ` Paul Mackerras [this message]
2018-12-07 11:42       ` Paul Mackerras
2018-12-18  1:00   ` Paul Mackerras
2018-12-18  1:00     ` Paul Mackerras
2018-12-07  3:43 ` [PATCH 1/8] KVM: PPC: Only report KVM_CAP_SPAPR_TCE_VFIO on powernv machines Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH 2/8] KVM: PPC: Book3S HV: Add function kvmhv_vcpu_is_radix() Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH 3/8] KVM: PPC: Book3S HV: Implement functions to access quadrants 1 & 2 Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH 4/8] KVM: PPC: Add load_from_eaddr and store_to_eaddr to the kvmppc_ops struct Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH 5/8] KVM: PPC: Update kvmppc_st and kvmppc_ld to use quadrants Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH 6/8] KVM: PPC: Book3S HV: Allow passthrough of an emulated device to an L2 guest Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH 7/8] KVM: PPC: Introduce new hcall H_COPY_TOFROM_GUEST to access quadrants 1 & 2 Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:43 ` [PATCH 8/8] KVM: PPC: Book3S HV: Allow passthrough of an emulated device to an L3 guest Suraj Jitindar Singh
2018-12-07  3:43   ` Suraj Jitindar Singh
2018-12-07  3:45 ` [PATCH 0/8] KVM: PPC: Implement passthrough of emulated devices for nested guests Suraj Jitindar Singh
2018-12-07  3:45   ` Suraj Jitindar Singh
  -- strict thread matches above, loose matches on Subject: below --
2018-12-07  1:17 [PATCH] KVM: PPC: Book3S PR: Set hflag to indicate that POWER9 supports 1T segments Suraj Jitindar Singh

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