From: Mark Brown <broonie@kernel.org>
To: Marc Zyngier <maz@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Sudeep Holla <sudeep.holla@arm.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v1 2/2] arm64: smccc: Support SMCCC v1.3 SVE register saving hint
Date: Tue, 18 May 2021 12:53:48 +0100 [thread overview]
Message-ID: <20210518115348.GA4358@sirena.org.uk> (raw)
In-Reply-To: <87pmxotirl.wl-maz@kernel.org>
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On Tue, May 18, 2021 at 11:53:50AM +0100, Marc Zyngier wrote:
> Mark Brown <broonie@kernel.org> wrote:
> > +alternative_if ARM64_SVE
> > +
> > + adrp x15, smccc_has_sve_hint
> The adrp instruction will give you a 4kB aligned address, which
> results in 1 chance out of 512 to point to the right location. The
> adr_l macro is probably what you want.
Ouch, yes. This was working surprisingly well in my testing.
> > register unsigned long r2 asm("r2"); \
> > register unsigned long r3 asm("r3"); \
> > __declare_args(__count_args(__VA_ARGS__), __VA_ARGS__); \
> > - asm volatile(inst "\n" : \
> > + asm volatile(SMCCC_SVE_CHECK \
> What happens when this is called from a context where
> __smccc_sve_check isn't mapped, nor does "current" mean anything? See
> arch/arm64/kvm/hyp/nvhe/psci-relay.c for an example.
Ah, oh dear. I have to admit I haven't entirely been able to follow the
contexts the various bits of KVM run in yet, nor how much of the normal
kernel environment is being maintained :/ . I do see some ifdefery with
__KVM_NVHE_HYPERVISOR__ elsewhere which could be used to take care of
that particular case either by providing a __hyp mapping or just not
trying to set the flag there (the latter seems safer) but I'm guessing
there's others. Do we have a reliable way of identifying such contexts?
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next prev parent reply other threads:[~2021-05-18 11:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-18 10:09 [PATCH v1 0/2] arm64: Implement SMCCC v1.3 SVE register saving hint Mark Brown
2021-05-18 10:09 ` [PATCH v1 1/2] arm64: asmlinkage: Enable use of BTI_C macro in SYM_CODE Mark Brown
2021-05-18 10:09 ` [PATCH v1 2/2] arm64: smccc: Support SMCCC v1.3 SVE register saving hint Mark Brown
2021-05-18 10:53 ` Marc Zyngier
2021-05-18 11:53 ` Mark Brown [this message]
2021-05-18 12:14 ` Marc Zyngier
2021-05-18 13:01 ` Mark Brown
2021-05-18 16:53 ` Ard Biesheuvel
2021-05-18 16:43 ` Sudeep Holla
2021-05-18 16:55 ` Mark Brown
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