linux-kernel - Re: [PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted

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Message-ID: <e21481a9-3e36-4a5d-9428-0f5ef8083676@redhat.com>
Date: Tue, 8 Oct 2024 10:31:06 +1000
From: Gavin Shan <gshan@...hat.com>
To: Steven Price <steven.price@....com>, kvm@...r.kernel.org,
 kvmarm@...ts.linux.dev
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
 Catalin Marinas <catalin.marinas@....com>, Marc Zyngier <maz@...nel.org>,
 Will Deacon <will@...nel.org>, James Morse <james.morse@....com>,
 Oliver Upton <oliver.upton@...ux.dev>, Zenghui Yu <yuzenghui@...wei.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Joey Gouly <joey.gouly@....com>, Alexandru Elisei
 <alexandru.elisei@....com>, Christoffer Dall <christoffer.dall@....com>,
 Fuad Tabba <tabba@...gle.com>, linux-coco@...ts.linux.dev,
 Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>,
 Shanker Donthineni <sdonthineni@...dia.com>, Alper Gun
 <alpergun@...gle.com>, "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>
Subject: Re: [PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted

On 10/5/24 12:43 AM, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@....com>
> 
> Instead of marking every MMIO as shared, check if the given region is
> "Protected" and apply the permissions accordingly.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> Signed-off-by: Steven Price <steven.price@....com>
> ---
> New patch for v5
> ---
>   arch/arm64/kernel/rsi.c | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 

With the following potential issue addressed:

Reviewed-by: Gavin Shan <gshan@...hat.com>

> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
> index d7bba4cee627..f1add76f89ce 100644
> --- a/arch/arm64/kernel/rsi.c
> +++ b/arch/arm64/kernel/rsi.c
> @@ -6,6 +6,8 @@
>   #include <linux/jump_label.h>
>   #include <linux/memblock.h>
>   #include <linux/psci.h>
> +
> +#include <asm/io.h>
>   #include <asm/rsi.h>
>   
>   struct realm_config config;
> @@ -92,6 +94,16 @@ bool arm64_is_protected_mmio(phys_addr_t base, size_t size)
>   }
>   EXPORT_SYMBOL(arm64_is_protected_mmio);
>   
> +static int realm_ioremap_hook(phys_addr_t phys, size_t size, pgprot_t *prot)
> +{
> +	if (arm64_is_protected_mmio(phys, size))
> +		*prot = pgprot_encrypted(*prot);
> +	else
> +		*prot = pgprot_decrypted(*prot);
> +
> +	return 0;
> +}
> +

We probably need arm64_is_mmio_private() here, meaning arm64_is_protected_mmio() isn't
sufficient to avoid invoking SMCCC call SMC_RSI_IPA_STATE_GET in a regular guest where
realm capability isn't present.

>   void __init arm64_rsi_init(void)
>   {
>   	if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_SMC)
> @@ -102,6 +114,9 @@ void __init arm64_rsi_init(void)
>   		return;
>   	prot_ns_shared = BIT(config.ipa_bits - 1);
>   
> +	if (arm64_ioremap_prot_hook_register(realm_ioremap_hook))
> +		return;
> +
>   	arm64_rsi_setup_memory();
>   
>   	static_branch_enable(&rsi_present);

Thanks,
Gavin