This is the mail archive of the
libc-alpha@sourceware.org
mailing list for the glibc project.
Re: [PATCH 21/27] arm64/sve: KVM: Prevent guests from using SVE
- From: Marc Zyngier <marc dot zyngier at arm dot com>
- To: Dave Martin <Dave dot Martin at arm dot com>, g at e103592 dot cambridge dot arm dot com
- Cc: linux-arm-kernel at lists dot infradead dot org, linux-arch at vger dot kernel dot org, libc-alpha at sourceware dot org, Ard Biesheuvel <ard dot biesheuvel at linaro dot org>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, Catalin Marinas <catalin dot marinas at arm dot com>, Will Deacon <will dot deacon at arm dot com>, Richard Sandiford <richard dot sandiford at arm dot com>, kvmarm at lists dot cs dot columbia dot edu, Christoffer Dall <christoffer dot dall at linaro dot org>
- Date: Wed, 16 Aug 2017 12:22:47 +0100
- Subject: Re: [PATCH 21/27] arm64/sve: KVM: Prevent guests from using SVE
- Authentication-results: sourceware.org; auth=none
- References: <1502280338-23002-1-git-send-email-Dave.Martin@arm.com> <1502280338-23002-22-git-send-email-Dave.Martin@arm.com> <0f5b14a8-4d04-61e4-05e8-92cd55c8bee9@arm.com> <20170816105013.GZ6321@e103592.cambridge.arm.com> <3cb51836-9677-5eb5-cc07-361eee674806@arm.com>
On 16/08/17 12:20, 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
Of course, the days of the ARMv7 ARM are still haunting me. This should
read DDI487B_a.
Apologies for the confusion.
M.
--
Jazz is not dead. It just smells funny...