From: Dave Martin <Dave.Martin@arm.com>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-arch@vger.kernel.org, libc-alpha@sourceware.org,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Christoffer Dall <christoffer.dall@linaro.org>,
Richard Sandiford <richard.sandiford@arm.com>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 21/27] arm64/sve: KVM: Prevent guests from using SVE
Date: Wed, 16 Aug 2017 12:35:19 +0100 [thread overview]
Message-ID: <20170816113519.GE6321@e103592.cambridge.arm.com> (raw)
In-Reply-To: <3cb51836-9677-5eb5-cc07-361eee674806@arm.com>
On Wed, Aug 16, 2017 at 12:20:41PM +0100, Marc Zyngier wrote:
> On 16/08/17 11:50, Dave Martin wrote:
> > On Tue, Aug 15, 2017 at 05:33:15PM +0100, Marc Zyngier wrote:
> >> On 09/08/17 13:05, Dave Martin wrote:
> >>> Until KVM has full SVE support, guests must not be allowed to
> >>> execute SVE instructions.
> >>>
> >>> This patch enables the necessary traps, and also ensures that the
> >>> traps are disabled again on exit from the guest so that the host
> >>> can still use SVE if it wants to.
> >>>
> >>> Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> >>> ---
> >>> arch/arm64/include/asm/kvm_arm.h | 3 ++-
> >>> arch/arm64/kvm/hyp/switch.c | 6 +++---
> >>> 2 files changed, 5 insertions(+), 4 deletions(-)
> >>>
> >>> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> >>> index dbf0537..8a19651 100644
> >>> --- a/arch/arm64/include/asm/kvm_arm.h
> >>> +++ b/arch/arm64/include/asm/kvm_arm.h
> >>> @@ -186,7 +186,7 @@
> >>> #define CPTR_EL2_TTA (1 << 20)
> >>> #define CPTR_EL2_TFP (1 << CPTR_EL2_TFP_SHIFT)
> >>> #define CPTR_EL2_TZ (1 << 8)
> >>> -#define CPTR_EL2_DEFAULT 0x000033ff
> >>> +#define CPTR_EL2_DEFAULT (0x000033ff & ~CPTR_EL2_TZ)
> >>
> >> I must say I'm not overly fond of this construct. I'd rather introduce a
> >> RES1 field that matches the v8.2 description, instead of this ugly
> >> constant and something that clears it.
> >
> > Sorry, I don't get your meaning here. v8.2 neither immediately predates
> > or postdates SVE.
>
> The ARMv8 ARM (DDI406B_a, D7.2.19) says otherwise. This bit is only
> defined as having a possibility of being 0 on an v8.2 implementation if
> SVE is implemented.
Right. I was confused by the v8.2 reference, since if this weren't true
for v8.0 of the architecture, we couldn't simply change a compile time
constant here. In fact, there's a compatible retroactive change to all
arch versions >= v8.0.
> > What are you propsing?
>
> What I'm proposing is:
>
> #define CPTR_EL2_RES1 0x32ff
> #define CPTR_EL2_DEFAULT CPTR_EL2_RES1
>
> and none of that pointless constant clearing.
>
> > I guess we could just write 0x000032ff now that the only meaning the
> > architecture can ever assign to bit 8 is known.
> Exactly.
OK, good -- I'll change that.
I was trying to avoid magic numberness, but it's a bit futile when
talking about RESx bits.
Cheers
---Dave
next prev parent reply other threads:[~2017-08-16 11:35 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-09 12:05 [PATCH 00/27] ARM Scalable Vector Extension (SVE) Dave Martin
2017-08-09 12:05 ` [PATCH 01/27] regset: Add support for dynamically sized regsets Dave Martin
2017-08-18 11:52 ` Alex Bennée
2017-08-09 12:05 ` [PATCH 02/27] arm64: KVM: Hide unsupported AArch64 CPU features from guests Dave Martin
2017-08-16 11:10 ` Marc Zyngier
2017-08-16 20:32 ` Dave Martin
2017-08-17 8:45 ` Marc Zyngier
2017-08-17 9:57 ` Dave Martin
2017-08-09 12:05 ` [PATCH 03/27] arm64: efi: Add missing Kconfig dependency on KERNEL_MODE_NEON Dave Martin
2017-08-18 12:02 ` Alex Bennée
2017-08-09 12:05 ` [PATCH 04/27] arm64: Port deprecated instruction emulation to new sysctl interface Dave Martin
2017-08-18 12:09 ` Alex Bennée
2017-08-09 12:05 ` [PATCH 05/27] arm64: fpsimd: Simplify uses of {set,clear}_ti_thread_flag() Dave Martin
2017-08-15 17:11 ` Ard Biesheuvel
2017-08-18 16:36 ` [PATCH 05/27] arm64: fpsimd: Simplify uses of {set, clear}_ti_thread_flag() Alex Bennée
2017-08-09 12:05 ` [PATCH 06/27] arm64/sve: System register and exception syndrome definitions Dave Martin
2017-08-21 9:33 ` Alex Bennée
2017-08-21 12:34 ` Alex Bennée
2017-08-21 14:26 ` Dave Martin
2017-08-21 14:50 ` Alex Bennée
2017-08-21 15:19 ` Dave Martin
2017-08-21 15:34 ` Alex Bennée
2017-08-21 13:56 ` Dave Martin
2017-08-21 14:36 ` Alex Bennée
2017-08-09 12:05 ` [PATCH 07/27] arm64/sve: Low-level SVE architectural state manipulation functions Dave Martin
2017-08-21 10:11 ` Alex Bennée
2017-08-21 14:38 ` Dave Martin
2017-08-09 12:05 ` [PATCH 08/27] arm64/sve: Kconfig update and conditional compilation support Dave Martin
2017-08-21 10:12 ` Alex Bennée
2017-08-09 12:05 ` [PATCH 09/27] arm64/sve: Signal frame and context structure definition Dave Martin
2017-08-22 10:22 ` Alex Bennée
2017-08-22 11:17 ` Dave Martin
2017-08-22 13:53 ` Alex Bennée
2017-08-22 14:21 ` Dave Martin
2017-08-22 15:03 ` Alex Bennée
2017-08-22 15:41 ` Dave Martin
2017-08-09 12:05 ` [PATCH 10/27] arm64/sve: Low-level CPU setup Dave Martin
2017-08-22 15:04 ` Alex Bennée
2017-08-22 15:33 ` Dave Martin
2017-08-09 12:05 ` [PATCH 11/27] arm64/sve: Core task context handling Dave Martin
2017-08-15 17:31 ` Ard Biesheuvel
2017-08-16 10:40 ` Dave Martin
2017-08-17 16:42 ` Dave Martin
2017-08-17 16:46 ` Ard Biesheuvel
2017-08-22 16:21 ` Alex Bennée
2017-08-22 17:19 ` Dave Martin
2017-08-22 18:39 ` Alex Bennée
2017-08-09 12:05 ` [PATCH 12/27] arm64/sve: Support vector length resetting for new processes Dave Martin
2017-08-22 16:22 ` Alex Bennée
2017-08-22 17:22 ` Dave Martin
2017-08-09 12:05 ` [PATCH 13/27] arm64/sve: Signal handling support Dave Martin
2017-08-23 9:38 ` Alex Bennée
2017-08-23 11:30 ` Dave Martin
2017-08-09 12:05 ` [PATCH 14/27] arm64/sve: Backend logic for setting the vector length Dave Martin
2017-08-23 15:33 ` Alex Bennée
2017-08-23 17:29 ` Dave Martin
2017-08-09 12:05 ` [PATCH 15/27] arm64/sve: Probe SVE capabilities and usable vector lengths Dave Martin
2017-08-16 17:48 ` Suzuki K Poulose
2017-08-17 10:04 ` Dave Martin
2017-08-17 10:46 ` Suzuki K Poulose
2017-08-09 12:05 ` [PATCH 16/27] arm64/sve: Preserve SVE registers around kernel-mode NEON use Dave Martin
2017-08-15 17:37 ` Ard Biesheuvel
2017-08-09 12:05 ` [PATCH 17/27] arm64/sve: Preserve SVE registers around EFI runtime service calls Dave Martin
2017-08-15 17:44 ` Ard Biesheuvel
2017-08-16 9:13 ` Dave Martin
2017-08-09 12:05 ` [PATCH 18/27] arm64/sve: ptrace and ELF coredump support Dave Martin
2017-08-09 12:05 ` [PATCH 19/27] arm64/sve: Add prctl controls for userspace vector length management Dave Martin
2017-08-09 12:05 ` [PATCH 20/27] arm64/sve: Add sysctl to set the default vector length for new processes Dave Martin
2017-08-09 12:05 ` [PATCH 21/27] arm64/sve: KVM: Prevent guests from using SVE Dave Martin
2017-08-15 16:33 ` Marc Zyngier
2017-08-16 10:50 ` Dave Martin
2017-08-16 11:20 ` Marc Zyngier
2017-08-16 11:22 ` Marc Zyngier
2017-08-16 11:35 ` Dave Martin [this message]
2017-08-09 12:05 ` [PATCH 22/27] arm64/sve: KVM: Treat guest SVE use as undefined instruction execution Dave Martin
2017-08-09 12:05 ` [PATCH 23/27] arm64/sve: KVM: Hide SVE from CPU features exposed to guests Dave Martin
2017-08-15 16:37 ` Marc Zyngier
2017-08-16 10:54 ` Dave Martin
2017-08-16 11:10 ` Marc Zyngier
2017-08-16 11:22 ` Dave Martin
2017-08-09 12:05 ` [PATCH 24/27] arm64/sve: Detect SVE and activate runtime support Dave Martin
2017-08-16 17:53 ` Suzuki K Poulose
2017-08-17 10:00 ` Dave Martin
2017-08-09 12:05 ` [PATCH 25/27] arm64/sve: Add documentation Dave Martin
2017-08-09 12:05 ` [RFC PATCH 26/27] arm64: signal: Report signal frame size to userspace via auxv Dave Martin
2017-08-09 12:05 ` [RFC PATCH 27/27] arm64/sve: signal: Include SVE when computing AT_MINSIGSTKSZ Dave Martin
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170816113519.GE6321@e103592.cambridge.arm.com \
--to=dave.martin@arm.com \
--cc=ard.biesheuvel@linaro.org \
--cc=catalin.marinas@arm.com \
--cc=christoffer.dall@linaro.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=libc-alpha@sourceware.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=marc.zyngier@arm.com \
--cc=richard.sandiford@arm.com \
--cc=szabolcs.nagy@arm.com \
--cc=will.deacon@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox