From: Paul Mackerras <paulus@ozlabs.org>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: linuxppc-dev@ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v3 29/33] KVM: PPC: Book3S HV: Handle differing endianness for H_ENTER_NESTED
Date: Thu, 04 Oct 2018 09:29:38 +0000 [thread overview]
Message-ID: <20181004092938.GB3255@fergus> (raw)
In-Reply-To: <20181003061336.GV1886@umbus.fritz.box>
On Wed, Oct 03, 2018 at 04:13:36PM +1000, David Gibson wrote:
> On Tue, Oct 02, 2018 at 09:31:28PM +1000, Paul Mackerras wrote:
> > From: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> >
> > The hcall H_ENTER_NESTED takes as the two parameters the address in
> > L1 guest memory of a hv_regs struct and a pt_regs struct which the
> > L1 guest would like to use to run a L2 guest and in which are returned
> > the exit state of the L2 guest. For efficiency, these are in the
> > endianness of the L1 guest, rather than being always big-endian as is
> > usually the case for PAPR hypercalls.
>
> Does that actually make a difference for efficiency? I thought the
> presence of the byte-reversing loads and stores meant byteswapping was
> basically zero-cost on POWER.
It means that the L1 hypervisor can pass a pointer to the regs struct
in the kvm_vcpu struct rather than having to make a copy, and copy the
values back after the H_ENTER_NESTED. I'll reword the commit message
to say it's mostly about convenience and to a lesser extent about
performance.
Paul.
WARNING: multiple messages have this Message-ID (diff)
From: Paul Mackerras <paulus@ozlabs.org>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: linuxppc-dev@ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v3 29/33] KVM: PPC: Book3S HV: Handle differing endianness for H_ENTER_NESTED
Date: Thu, 4 Oct 2018 19:29:38 +1000 [thread overview]
Message-ID: <20181004092938.GB3255@fergus> (raw)
In-Reply-To: <20181003061336.GV1886@umbus.fritz.box>
On Wed, Oct 03, 2018 at 04:13:36PM +1000, David Gibson wrote:
> On Tue, Oct 02, 2018 at 09:31:28PM +1000, Paul Mackerras wrote:
> > From: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
> >
> > The hcall H_ENTER_NESTED takes as the two parameters the address in
> > L1 guest memory of a hv_regs struct and a pt_regs struct which the
> > L1 guest would like to use to run a L2 guest and in which are returned
> > the exit state of the L2 guest. For efficiency, these are in the
> > endianness of the L1 guest, rather than being always big-endian as is
> > usually the case for PAPR hypercalls.
>
> Does that actually make a difference for efficiency? I thought the
> presence of the byte-reversing loads and stores meant byteswapping was
> basically zero-cost on POWER.
It means that the L1 hypervisor can pass a pointer to the regs struct
in the kvm_vcpu struct rather than having to make a copy, and copy the
values back after the H_ENTER_NESTED. I'll reword the commit message
to say it's mostly about convenience and to a lesser extent about
performance.
Paul.
next prev parent reply other threads:[~2018-10-04 9:29 UTC|newest]
Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-02 11:30 [PATCH v3 00/33] KVM: PPC: Book3S HV: Nested HV virtualization Paul Mackerras
2018-10-02 11:30 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 01/33] powerpc: Turn off CPU_FTR_P9_TM_HV_ASSIST in non-hypervisor mode Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 02/33] KVM: PPC: Book3S: Simplify external interrupt handling Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 03/33] KVM: PPC: Book3S HV: Remove left-over code in XICS-on-XIVE emulation Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 04/33] KVM: PPC: Book3S HV: Move interrupt delivery on guest entry to C code Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 05/33] KVM: PPC: Book3S HV: Extract PMU save/restore operations as C-callable functions Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 06/33] KVM: PPC: Book3S HV: Simplify real-mode interrupt handling Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 07/33] KVM: PPC: Book3S: Rework TM save/restore code and make it C-callable Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 08/33] KVM: PPC: Book3S HV: Call kvmppc_handle_exit_hv() with vcore unlocked Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 09/33] KVM: PPC: Book3S HV: Streamlined guest entry/exit path on P9 for radix guests Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 10/33] KVM: PPC: Book3S HV: Handle hypervisor instruction faults better Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 11/33] KVM: PPC: Book3S HV: Add a debugfs file to dump radix mappings Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 12/33] KVM: PPC: Use ccr field in pt_regs struct embedded in vcpu struct Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 13/33] KVM: PPC: Book3S HV: Clear partition table entry on vm teardown Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 14/33] KVM: PPC: Book3S HV: Make kvmppc_mmu_radix_xlate process/partition table agnostic Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 15/33] KVM: PPC: Book3S HV: Refactor radix page fault handler Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 16/33] KVM: PPC: Book3S HV: Use kvmppc_unmap_pte() in kvm_unmap_radix() Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 17/33] KVM: PPC: Book3S HV: Framework and hcall stubs for nested virtualization Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 3:17 ` David Gibson
2018-10-03 3:17 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 18/33] KVM: PPC: Book3S HV: Nested guest entry via hypercall Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 5:12 ` David Gibson
2018-10-03 5:12 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 19/33] KVM: PPC: Book3S HV: Use XICS hypercalls when running as a nested hypervisor Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 20/33] KVM: PPC: Book3S HV: Handle hypercalls correctly when nested Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 21/33] KVM: PPC: Book3S HV: Framework to handle HV Emulation Assist Interrupt Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 5:13 ` David Gibson
2018-10-03 5:13 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 22/33] KVM: PPC: Book3S HV: Handle page fault for a nested guest Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 5:39 ` David Gibson
2018-10-03 5:39 ` David Gibson
2018-10-03 5:42 ` David Gibson
2018-10-03 5:42 ` David Gibson
2018-10-04 9:21 ` Paul Mackerras
2018-10-04 9:21 ` Paul Mackerras
2018-10-05 2:46 ` David Gibson
2018-10-05 2:46 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 23/33] KVM: PPC: Book3S HV: Introduce rmap to track nested guest mappings Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 5:56 ` David Gibson
2018-10-03 5:56 ` David Gibson
2018-10-04 3:05 ` Paul Mackerras
2018-10-04 3:05 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 24/33] KVM: PPC: Book3S HV: Emulate Privileged TLBIE for guest hypervisors Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 5:56 ` David Gibson
2018-10-03 5:56 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 25/33] KVM: PPC: Book3S HV: Invalidate TLB when nested vcpu moves physical cpu Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 26/33] KVM: PPC: Book3S HV: Don't access HFSCR, LPIDR or LPCR when running nested Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 27/33] KVM: PPC: Book3S HV: Add one-reg interface to virtual PTCR register Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 28/33] KVM: PPC: Book3S HV: Sanitise hv_regs on nested guest entry Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 6:07 ` David Gibson
2018-10-03 6:07 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 29/33] KVM: PPC: Book3S HV: Handle differing endianness for H_ENTER_NESTED Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 6:13 ` David Gibson
2018-10-03 6:13 ` David Gibson
2018-10-04 9:29 ` Paul Mackerras [this message]
2018-10-04 9:29 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 30/33] KVM: PPC: Book3S HV: Allow HV module to load without hypervisor mode Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 6:15 ` David Gibson
2018-10-03 6:15 ` David Gibson
2018-10-04 3:03 ` Paul Mackerras
2018-10-04 3:03 ` Paul Mackerras
2018-10-05 3:05 ` David Gibson
2018-10-05 3:05 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 31/33] KVM: PPC: Book3S HV: Add nested shadow page tables to debugfs Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-02 11:31 ` [PATCH v3 32/33] KVM: PPC: Book3S HV: Use hypercalls for TLB invalidation when nested Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 6:17 ` David Gibson
2018-10-03 6:17 ` David Gibson
2018-10-02 11:31 ` [PATCH v3 33/33] KVM: PPC: Book3S HV: Add a VM capability to enable nested virtualization Paul Mackerras
2018-10-02 11:31 ` Paul Mackerras
2018-10-03 6:21 ` David Gibson
2018-10-03 6:21 ` David Gibson
2018-10-04 9:48 ` Paul Mackerras
2018-10-04 9:48 ` Paul Mackerras
2018-10-05 3:29 ` David Gibson
2018-10-05 3:29 ` David Gibson
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