From: David Gibson <david@gibson.dropbear.id.au>
To: Paul Mackerras <paulus@ozlabs.org>
Cc: linuxppc-dev@ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v4 25/32] KVM: PPC: Book3S HV: Invalidate TLB when nested vcpu moves physical cpu
Date: Fri, 5 Oct 2018 14:54:28 +1000 [thread overview]
Message-ID: <20181005045428.GO7004@umbus.fritz.box> (raw)
In-Reply-To: <20181005042350.GA3309@fergus>
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On Fri, Oct 05, 2018 at 02:23:50PM +1000, Paul Mackerras wrote:
> On Fri, Oct 05, 2018 at 02:09:08PM +1000, David Gibson wrote:
> > On Thu, Oct 04, 2018 at 09:56:02PM +1000, Paul Mackerras wrote:
> > > From: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> > >
> > > This is only done at level 0, since only level 0 knows which physical
> > > CPU a vcpu is running on. This does for nested guests what L0 already
> > > did for its own guests, which is to flush the TLB on a pCPU when it
> > > goes to run a vCPU there, and there is another vCPU in the same VM
> > > which previously ran on this pCPU and has now started to run on another
> > > pCPU. This is to handle the situation where the other vCPU touched
> > > a mapping, moved to another pCPU and did a tlbiel (local-only tlbie)
> > > on that new pCPU and thus left behind a stale TLB entry on this pCPU.
> > >
> > > This introduces a limit on the the vcpu_token values used in the
> > > H_ENTER_NESTED hcall -- they must now be less than NR_CPUS.
> >
> > This does make the vcpu tokens no longer entirely opaque to the L0.
> > It works for now, because the only L1 is Linux and we know basically
> > how it allocates those tokens. Eventually we probably want some way
> > to either remove this restriction or to advertise the limit to the L1.
>
> Right, we could use something like a hash table and have it be
> basically just as efficient as the array when the set of IDs is dense
> while also handling arbitrary ID values. (We'd have to make sure that
> L1 couldn't trigger unbounded memory consumption in L0, though.)
Another approach would be to sacifice some performance for L0
simplicity: when an L1 vCPU changes pCPU, flush all the nested LPIDs
associated with that L1. When an L2 vCPU changes L1 vCPU (and
therefore, indirectly pCPU), the L1 would be responsible for flushing
it.
--
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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next prev parent reply other threads:[~2018-10-05 5:35 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-04 11:55 [PATCH v4 00/32] KVM: PPC: Book3S HV: Nested HV virtualization Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 01/32] powerpc: Turn off CPU_FTR_P9_TM_HV_ASSIST in non-hypervisor mode Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 02/32] KVM: PPC: Book3S: Simplify external interrupt handling Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 03/32] KVM: PPC: Book3S HV: Remove left-over code in XICS-on-XIVE emulation Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 04/32] KVM: PPC: Book3S HV: Move interrupt delivery on guest entry to C code Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 05/32] KVM: PPC: Book3S HV: Extract PMU save/restore operations as C-callable functions Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 06/32] KVM: PPC: Book3S HV: Simplify real-mode interrupt handling Paul Mackerras
2018-10-05 4:18 ` David Gibson
2018-10-04 11:55 ` [PATCH v4 07/32] KVM: PPC: Book3S: Rework TM save/restore code and make it C-callable Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 08/32] KVM: PPC: Book3S HV: Call kvmppc_handle_exit_hv() with vcore unlocked Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 09/32] KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 10/32] KVM: PPC: Book3S HV: Handle hypervisor instruction faults better Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 11/32] KVM: PPC: Book3S HV: Add a debugfs file to dump radix mappings Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 12/32] KVM: PPC: Use ccr field in pt_regs struct embedded in vcpu struct Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 13/32] KVM: PPC: Book3S HV: Clear partition table entry on vm teardown Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 14/32] KVM: PPC: Book3S HV: Make kvmppc_mmu_radix_xlate process/partition table agnostic Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 15/32] KVM: PPC: Book3S HV: Refactor radix page fault handler Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 16/32] KVM: PPC: Book3S HV: Use kvmppc_unmap_pte() in kvm_unmap_radix() Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 17/32] KVM: PPC: Book3S HV: Framework and hcall stubs for nested virtualization Paul Mackerras
2018-10-05 4:12 ` David Gibson
2018-10-04 11:55 ` [PATCH v4 18/32] KVM: PPC: Book3S HV: Nested guest entry via hypercall Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 19/32] KVM: PPC: Book3S HV: Use XICS hypercalls when running as a nested hypervisor Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 20/32] KVM: PPC: Book3S HV: Handle hypercalls correctly when nested Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 21/32] KVM: PPC: Book3S HV: Handle page fault for a nested guest Paul Mackerras
2018-10-04 11:55 ` [PATCH v4 22/32] KVM: PPC: Book3S HV: Introduce rmap to track nested guest mappings Paul Mackerras
2018-10-05 2:49 ` David Gibson
2018-10-04 11:56 ` [PATCH v4 23/32] KVM: PPC: Book3S HV: Implement H_TLB_INVALIDATE hcall Paul Mackerras
2018-10-05 3:40 ` David Gibson
2018-10-04 11:56 ` [PATCH v4 24/32] KVM: PPC: Book3S HV: Use hypercalls for TLB invalidation when nested Paul Mackerras
2018-10-05 3:45 ` David Gibson
2018-10-04 11:56 ` [PATCH v4 25/32] KVM: PPC: Book3S HV: Invalidate TLB when nested vcpu moves physical cpu Paul Mackerras
2018-10-05 4:09 ` David Gibson
2018-10-05 4:23 ` Paul Mackerras
2018-10-05 4:54 ` David Gibson [this message]
2018-10-05 5:32 ` Paul Mackerras
2018-10-08 2:02 ` David Gibson
2018-10-04 11:56 ` [PATCH v4 26/32] KVM: PPC: Book3S HV: Don't access HFSCR, LPIDR or LPCR when running nested Paul Mackerras
2018-10-04 11:56 ` [PATCH v4 27/32] KVM: PPC: Book3S HV: Add one-reg interface to virtual PTCR register Paul Mackerras
2018-10-04 11:56 ` [PATCH v4 28/32] KVM: PPC: Book3S HV: Sanitise hv_regs on nested guest entry Paul Mackerras
2018-10-04 11:56 ` [PATCH v4 29/32] KVM: PPC: Book3S HV: Handle differing endianness for H_ENTER_NESTED Paul Mackerras
2018-10-04 11:56 ` [PATCH v4 30/32] KVM: PPC: Book3S HV: Allow HV module to load without hypervisor mode Paul Mackerras
2018-10-05 3:05 ` David Gibson
2018-10-04 11:56 ` [PATCH v4 31/32] KVM: PPC: Book3S HV: Add nested shadow page tables to debugfs Paul Mackerras
2018-10-04 11:56 ` [PATCH v4 32/32] KVM: PPC: Book3S HV: Add a VM capability to enable nested virtualization Paul Mackerras
2018-10-05 3:06 ` David Gibson
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