From: christoffer.dall@linaro.org (Christoffer Dall)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 10/21] arm64: KVM: VHE: Split save/restore of sysregs shared between EL1 and EL2
Date: Tue, 2 Feb 2016 21:07:20 +0100 [thread overview]
Message-ID: <20160202200720.GH6190@cbox> (raw)
In-Reply-To: <56B0D720.9000901@arm.com>
On Tue, Feb 02, 2016 at 04:19:44PM +0000, Marc Zyngier wrote:
> On 02/02/16 15:46, Christoffer Dall wrote:
> > On Tue, Feb 02, 2016 at 09:46:05AM +0000, Marc Zyngier wrote:
> >> On 01/02/16 13:54, Christoffer Dall wrote:
> >>> On Mon, Jan 25, 2016 at 03:53:44PM +0000, Marc Zyngier wrote:
> >>>> A handful of system registers are still shared between EL1 and EL2,
> >>>> even while using VHE. These are tpidr*_el[01], actlr_el1, sp0, elr,
> >>>> and spsr.
> >>>
> >>> So by shared registers you mean registers that do both have an EL0/1
> >>> version as well as an EL2 version, but where accesses aren't rewritten
> >>> transparently?
> >>
> >> No, I mean that these registers do *not* have a separate banked version.
> >> There is only a single set of registers, which have to be save/restored
> >> the old way.
> >
> > huh, ARMv8 clearly specifies the existence of TPIDR_EL0, TPIDR_EL1, and
> > TPIDR_EL2, for example.
> >
> > I cannot seem to find anywhere in the VHE spec that says that the
> > TPIDR_EL2 goes away. I'm confused now.
>
> Nothing goes away, but these registers do not get renamed either. For
> example, TPIDR_EL1 doesn't magically access TPIDR_EL2 when running at
> EL2+VHE, and there is no TPIDR_EL12 accessor either.
>
> So TPIDR_EL1 is effectively "shared" between host and guest, and must be
> save/restored (note that the host kernel still uses TIPDR_EL1 even when
> running with VHE, and that KVM still uses TPIDR_EL2 to cache the current
> vcpu).
>
ok, I can understand as long as we're saying a register is shared
between the host and the guest, but it was the "registers are shared
between EL1 and EL2" that threw me off.
> >>
> >>>
> >>> also, by sp0 do you mean sp_el0, and by elr you mean elr_el1, and by
> >>> spsr you mean spsr_el1 ?
> >>
> >> sp0 -> sp_el0 indeed. elr and spsr really are the guest PC and PSTATE,
> >> so I should really reword this commit message, it is utterly confusing.
> >>
> > I guess I don't understand the definition of a 'shared' register given
> > your comments here...
>
> Does this make it clearer?
>
yes. You could change the host to path it when using VHE to use
TPIDR_EL2 if you wanted and store the vcpu pointer on the stack while
running the guest, but there's probably no real benefit of doing so.
I'll be shutting up now...
Thanks,
-Christoffer
next prev parent reply other threads:[~2016-02-02 20:07 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-25 15:53 [PATCH v2 00/21] arm64: Virtualization Host Extension support Marc Zyngier
2016-01-25 15:53 ` [PATCH v2 01/21] arm/arm64: Add new is_kernel_in_hyp_mode predicate Marc Zyngier
2016-02-01 13:59 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 02/21] arm64: Allow the arch timer to use the HYP timer Marc Zyngier
2016-02-01 12:29 ` Christoffer Dall
2016-02-01 13:42 ` Marc Zyngier
2016-02-01 15:37 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 03/21] arm64: Add ARM64_HAS_VIRT_HOST_EXTN feature Marc Zyngier
2016-02-01 13:59 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 04/21] arm64: KVM: Skip HYP setup when already running in HYP Marc Zyngier
2016-02-01 13:59 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 05/21] arm64: KVM: VHE: Turn VTCR_EL2 setup into a reusable macro Marc Zyngier
2016-02-01 13:13 ` Christoffer Dall
2016-02-01 14:21 ` Marc Zyngier
2016-02-01 15:38 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 06/21] arm64: KVM: VHE: Patch out use of HVC Marc Zyngier
2016-02-01 13:16 ` Christoffer Dall
2016-02-01 13:34 ` Marc Zyngier
2016-02-01 15:36 ` Catalin Marinas
2016-02-01 16:20 ` Marc Zyngier
2016-02-01 17:08 ` Ard Biesheuvel
2016-02-01 17:28 ` Marc Zyngier
2016-02-02 15:42 ` Christoffer Dall
2016-02-01 15:39 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 07/21] arm64: KVM: VHE: Patch out kern_hyp_va Marc Zyngier
2016-02-01 13:20 ` Christoffer Dall
2016-02-01 13:38 ` Marc Zyngier
2016-02-01 15:40 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 08/21] arm64: KVM: VHE: Introduce unified system register accessors Marc Zyngier
2016-02-01 13:47 ` Christoffer Dall
2016-02-01 14:04 ` Marc Zyngier
2016-02-01 15:43 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 09/21] arm64: KVM: VHE: Differenciate host/guest sysreg save/restore Marc Zyngier
2016-02-01 13:59 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 10/21] arm64: KVM: VHE: Split save/restore of sysregs shared between EL1 and EL2 Marc Zyngier
2016-02-01 13:54 ` Christoffer Dall
2016-02-02 9:46 ` Marc Zyngier
2016-02-02 15:46 ` Christoffer Dall
2016-02-02 16:19 ` Marc Zyngier
2016-02-02 20:07 ` Christoffer Dall [this message]
2016-01-25 15:53 ` [PATCH v2 11/21] arm64: KVM: VHE: Use unified system register accessors Marc Zyngier
2016-02-01 13:59 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 12/21] arm64: KVM: VHE: Enable minimal sysreg save/restore Marc Zyngier
2016-02-01 14:02 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 13/21] arm64: KVM: VHE: Make __fpsimd_enabled VHE aware Marc Zyngier
2016-02-01 14:17 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 14/21] arm64: KVM: VHE: Implement VHE activate/deactivate_traps Marc Zyngier
2016-02-01 14:20 ` Christoffer Dall
2016-02-02 11:27 ` Marc Zyngier
2016-01-25 15:53 ` [PATCH v2 15/21] arm64: KVM: VHE: Use unified sysreg accessors for timer Marc Zyngier
2016-02-01 14:23 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 16/21] arm64: KVM: VHE: Add fpsimd enabling on guest access Marc Zyngier
2016-02-01 14:24 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 17/21] arm64: KVM: VHE: Add alternative panic handling Marc Zyngier
2016-02-01 14:26 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 18/21] arm64: KVM: Introduce hyp_alternate_value helper Marc Zyngier
2016-02-01 14:41 ` Christoffer Dall
2016-02-02 13:42 ` Marc Zyngier
2016-02-02 15:47 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 19/21] arm64: KVM: Move most of the fault decoding to C Marc Zyngier
2016-02-01 15:21 ` Christoffer Dall
2016-02-02 14:24 ` Marc Zyngier
2016-02-02 15:50 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 20/21] arm64: VHE: Add support for running Linux in EL2 mode Marc Zyngier
2016-01-26 14:04 ` Suzuki K. Poulose
2016-01-26 14:30 ` Suzuki K. Poulose
2016-02-01 15:26 ` Christoffer Dall
2016-01-25 15:53 ` [PATCH v2 21/21] arm64: Panic when VHE and non VHE CPUs coexist Marc Zyngier
2016-01-26 14:25 ` Suzuki K. Poulose
2016-01-26 14:34 ` Marc Zyngier
2016-02-01 15:36 ` Christoffer Dall
2016-02-02 15:32 ` Marc Zyngier
2016-02-03 8:49 ` Christoffer Dall
2016-02-03 17:45 ` Marc Zyngier
2016-02-03 19:12 ` Christoffer Dall
2016-01-25 16:15 ` [PATCH v2 00/21] arm64: Virtualization Host Extension support Arnd Bergmann
2016-01-25 16:23 ` Marc Zyngier
2016-01-25 16:26 ` Arnd Bergmann
2016-01-25 16:26 ` Will Deacon
2016-01-25 16:37 ` Marc Zyngier
2016-01-25 16:44 ` Will Deacon
2016-01-25 19:16 ` Marc Zyngier
2016-02-01 16:25 ` Christoffer Dall
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