1. Patchew
  2. linux
  3. [PATCH v6 00/11] arm64: Support for running as a guest in Arm CCA
  4. View patch

[PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted

Steven Price posted 11 patches 1 month, 3 weeks ago
There is a newer version of this series
[PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted
Posted by Steven Price 1 month, 3 weeks ago 
From: Suzuki K Poulose <suzuki.poulose@arm.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@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
New patch for v5
---
 arch/arm64/kernel/rsi.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

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;
+}
+
 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);
-- 
2.34.1
Re: [PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted
Posted by Catalin Marinas 1 month, 2 weeks ago 
On Fri, Oct 04, 2024 at 03:43:00PM +0100, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.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@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Re: [PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted
Posted by Gavin Shan 1 month, 3 weeks ago 
On 10/5/24 12:43 AM, Steven Price wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.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@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.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@redhat.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
Re: [PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted
Posted by Catalin Marinas 1 month, 2 weeks ago 
On Tue, Oct 08, 2024 at 10:31:06AM +1000, Gavin Shan wrote:
> On 10/5/24 12:43 AM, Steven Price wrote:
> > 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.

I think we get away with this since the hook won't be registered in a
normal guest (done from arm64_rsi_init()). So the additional check in
arm64_is_mmio_private() is unnecessary.

-- 
Catalin
Re: [PATCH v6 05/11] arm64: rsi: Map unprotected MMIO as decrypted
Posted by Gavin Shan 1 month, 2 weeks ago 
On 10/11/24 11:19 PM, Catalin Marinas wrote:
> On Tue, Oct 08, 2024 at 10:31:06AM +1000, Gavin Shan wrote:
>> On 10/5/24 12:43 AM, Steven Price wrote:
>>> 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.
> 
> I think we get away with this since the hook won't be registered in a
> normal guest (done from arm64_rsi_init()). So the additional check in
> arm64_is_mmio_private() is unnecessary.
> 

Indeed. I missed the point that the hook won't be registered for a normal
guest. So we're good and safe.

Thanks,
Gavin

Patchew 2.1-devel-b67e4c2

© 2016 - 2024 Red Hat, Inc.