Re: [PATCH v1 16/24] kvm: arm64: Add offset for hyp VA <-> PA conversion

From: Marc Zyngier <maz@kernel.org>
To: David Brazdil <dbrazdil@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	kernel-team@android.com,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Andrew Walbran <qwandor@google.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Quentin Perret <qperret@google.com>,
	linux-kernel@vger.kernel.org, James Morse <james.morse@arm.com>,
	linux-arm-kernel@lists.infradead.org, Tejun Heo <tj@kernel.org>,
	Dennis Zhou <dennis@kernel.org>, Christoph Lameter <cl@linux.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Andrew Scull <ascull@google.com>
Subject: Re: [PATCH v1 16/24] kvm: arm64: Add offset for hyp VA <-> PA conversion
Date: Wed, 11 Nov 2020 13:47:28 +0000	[thread overview]
Message-ID: <ded6b623ea8ddc43f7dcabd0ec59d4b5@kernel.org> (raw)
In-Reply-To: <20201109113233.9012-17-dbrazdil@google.com>

On 2020-11-09 11:32, David Brazdil wrote:
> Add a host-initialized constant to KVM nVHE hyp code for converting
> between EL2 linear map virtual addresses and physical addresses.
> Also add `__hyp_pa` macro that performs the conversion.
> 
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
>  arch/arm64/kvm/arm.c           | 15 +++++++++++++++
>  arch/arm64/kvm/hyp/nvhe/psci.c |  3 +++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 28e3bc056225..dc7d43d7785a 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1484,6 +1484,20 @@ static inline void hyp_cpu_pm_exit(void)
>  }
>  #endif
> 
> +static void init_hyp_physvirt_offset(void)
> +{
> +	extern s64 kvm_nvhe_sym(hyp_physvirt_offset);
> +	unsigned long kern_vaddr, hyp_vaddr, paddr;
> +
> +	/* Check that kvm_arm_hyp_percpu_base has been set. */
> +	BUG_ON(kvm_arm_hyp_percpu_base[0] == 0);

Why is this dependent on the percpu base? Or is that just a convenient
symbol?

> +
> +	kern_vaddr = kvm_arm_hyp_percpu_base[0];
> +	hyp_vaddr = kern_hyp_va(kern_vaddr);
> +	paddr = __pa(kern_vaddr);
> +	CHOOSE_NVHE_SYM(hyp_physvirt_offset) = (s64)paddr - (s64)hyp_vaddr;
> +}

It feels like this offset could be set at the point where we compute
the hyp_va offset in va_layout.c, couldn't it? It would have the
advantage of keeping all the ugly VA hacks together.

> +
>  static void init_cpu_logical_map(void)
>  {
>  	extern u64 kvm_nvhe_sym(__cpu_logical_map)[NR_CPUS];
> @@ -1688,6 +1702,7 @@ static int init_hyp_mode(void)
>  		}
>  	}
> 
> +	init_hyp_physvirt_offset();
>  	init_cpu_logical_map();
>  	init_psci();
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci.c 
> b/arch/arm64/kvm/hyp/nvhe/psci.c
> index 82d3b2c89658..b0b5df590ba5 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci.c
> @@ -16,6 +16,9 @@
>  /* Config options set by the host. */
>  u32 kvm_host_psci_version = PSCI_VERSION(0, 0);
>  u32 kvm_host_psci_function_id[PSCI_FN_MAX];
> +s64 hyp_physvirt_offset;
> +
> +#define __hyp_pa(x) ((phys_addr_t)((x)) + hyp_physvirt_offset)
> 
>  static u64 get_psci_func_id(struct kvm_cpu_context *host_ctxt)
>  {

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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