Re: [PATCH v5 07/19] arm64: rsi: Add support for checking whether an MMIO is protected

[Gavin Shan <gshan@redhat.com>]

On 9/6/24 2:32 PM, Gavin Shan wrote:
> On 8/19/24 11:19 PM, Steven Price wrote:
>> From: Suzuki K Poulose <suzuki.poulose@arm.com>
>>
>> On Arm CCA, with RMM-v1.0, all MMIO regions are shared. However, in
>> the future, an Arm CCA-v1.0 compliant guest may be run in a lesser
>> privileged partition in the Realm World (with Arm CCA-v1.1 Planes
>> feature). In this case, some of the MMIO regions may be emulated
>> by a higher privileged component in the Realm world, i.e, protected.
>>
>> Thus the guest must decide today, whether a given MMIO region is shared
>> vs Protected and create the stage1 mapping accordingly. On Arm CCA, this
>> detection is based on the "IPA State" (RIPAS == RIPAS_IO). Provide a
>> helper to run this check on a given range of MMIO.
>>
>> Also, provide a arm64 helper which may be hooked in by other solutions.
>>
>> 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/include/asm/io.h       |  8 ++++++++
>>   arch/arm64/include/asm/rsi.h      |  3 +++
>>   arch/arm64/include/asm/rsi_cmds.h | 21 +++++++++++++++++++++
>>   arch/arm64/kernel/rsi.c           | 26 ++++++++++++++++++++++++++
>>   4 files changed, 58 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
>> index 1ada23a6ec19..a6c551c5e44e 100644
>> --- a/arch/arm64/include/asm/io.h
>> +++ b/arch/arm64/include/asm/io.h
>> @@ -17,6 +17,7 @@
>>   #include <asm/early_ioremap.h>
>>   #include <asm/alternative.h>
>>   #include <asm/cpufeature.h>
>> +#include <asm/rsi.h>
>>   /*
>>    * Generic IO read/write.  These perform native-endian accesses.
>> @@ -318,4 +319,11 @@ extern bool arch_memremap_can_ram_remap(resource_size_t offset, size_t size,
>>                       unsigned long flags);
>>   #define arch_memremap_can_ram_remap arch_memremap_can_ram_remap
>> +static inline bool arm64_is_iomem_private(phys_addr_t phys_addr, size_t size)
>> +{
>> +    if (unlikely(is_realm_world()))
>> +        return arm64_rsi_is_protected_mmio(phys_addr, size);
>> +    return false;
>> +}
>> +
>>   #endif    /* __ASM_IO_H */
>> diff --git a/arch/arm64/include/asm/rsi.h b/arch/arm64/include/asm/rsi.h
>> index 2bc013badbc3..e31231b50b6a 100644
>> --- a/arch/arm64/include/asm/rsi.h
>> +++ b/arch/arm64/include/asm/rsi.h
>> @@ -13,6 +13,9 @@ DECLARE_STATIC_KEY_FALSE(rsi_present);
>>   void __init arm64_rsi_init(void);
>>   void __init arm64_rsi_setup_memory(void);
>> +
>> +bool arm64_rsi_is_protected_mmio(phys_addr_t base, size_t size);
>> +
>>   static inline bool is_realm_world(void)
>>   {
>>       return static_branch_unlikely(&rsi_present);
>> diff --git a/arch/arm64/include/asm/rsi_cmds.h b/arch/arm64/include/asm/rsi_cmds.h
>> index 968b03f4e703..c2363f36d167 100644
>> --- a/arch/arm64/include/asm/rsi_cmds.h
>> +++ b/arch/arm64/include/asm/rsi_cmds.h
>> @@ -45,6 +45,27 @@ static inline unsigned long rsi_get_realm_config(struct realm_config *cfg)
>>       return res.a0;
>>   }
>> +static inline unsigned long rsi_ipa_state_get(phys_addr_t start,
>> +                          phys_addr_t end,
>> +                          enum ripas *state,
>> +                          phys_addr_t *top)
>> +{
>> +    struct arm_smccc_res res;
>> +
>> +    arm_smccc_smc(SMC_RSI_IPA_STATE_GET,
>> +              start, end, 0, 0, 0, 0, 0,
>> +              &res);
>> +
>> +    if (res.a0 == RSI_SUCCESS) {
>> +        if (top)
>> +            *top = res.a1;
>> +        if (state)
>> +            *state = res.a2;
>> +    }
>> +
>> +    return res.a0;
>> +}
>> +
>>   static inline unsigned long rsi_set_addr_range_state(phys_addr_t start,
>>                                phys_addr_t end,
>>                                enum ripas state,
>> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
>> index e968a5c9929e..381a5b9a5333 100644
>> --- a/arch/arm64/kernel/rsi.c
>> +++ b/arch/arm64/kernel/rsi.c
>> @@ -67,6 +67,32 @@ void __init arm64_rsi_setup_memory(void)
>>       }
>>   }
>> +bool arm64_rsi_is_protected_mmio(phys_addr_t base, size_t size)
>> +{
>> +    enum ripas ripas;
>> +    phys_addr_t end, top;
>> +
>> +    /* Overflow ? */
>> +    if (WARN_ON(base + size < base))
>> +        return false;
>> +
>> +    end = ALIGN(base + size, RSI_GRANULE_SIZE);
>> +    base = ALIGN_DOWN(base, RSI_GRANULE_SIZE);
>> +
>> +    while (base < end) {
>> +        if (WARN_ON(rsi_ipa_state_get(base, end, &ripas, &top)))
>> +            break;
>> +        if (WARN_ON(top <= base))
>> +            break;
>> +        if (ripas != RSI_RIPAS_IO)
>> +            break;
>> +        base = top;
>> +    }
>> +
>> +    return (size && base >= end);
>> +}
> 
> The unexpected calltrace is continuously observed with host/v4, guest/v5 and
> latest upstream tf-rmm on 'WARN_ON(top <= base)' because @top is never updated
> by the latest tf-rmm. The following call path indicates how SMC_RSI_IPA_STATE_GET
> is handled by tf-rmm. I don't see RSI_RIPAS_IO is defined there and @top is
> updated.
> 
> [    0.000000] ------------[ cut here ]------------
> [    0.000000] WARNING: CPU: 0 PID: 0 at arch/arm64/kernel/rsi.c:103 arm64_rsi_is_protected_mmio+0xf0/0x110
> [    0.000000] Modules linked in:
> [    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.11.0-rc1-gavin-g3527d001084e #1
> [    0.000000] Hardware name: linux,dummy-virt (DT)
> [    0.000000] pstate: 200000c5 (nzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [    0.000000] pc : arm64_rsi_is_protected_mmio+0xf0/0x110
> [    0.000000] lr : arm64_rsi_is_protected_mmio+0x80/0x110
> [    0.000000] sp : ffffcd7097053bf0
> [    0.000000] x29: ffffcd7097053c30 x28: 0000000000000000 x27: 0000000000000000
> [    0.000000] x26: 00000000000003d0 x25: 00000000ffffff8e x24: ffffcd7096831bd0
> [    0.000000] x23: ffffcd7097053c08 x22: 00000000c4000198 x21: 0000000000001000
> [    0.000000] x20: 0000000001001000 x19: 0000000001000000 x18: 0000000000000002
> [    0.000000] x17: 0000000000000000 x16: 0000000000000010 x15: 0001000080000000
> [    0.000000] x14: 0068000000000703 x13: ffffffffff5fe000 x12: ffffcd7097053ba4
> [    0.000000] x11: 00000000000003d0 x10: ffffcd7097053bc4 x9 : 0000000000000444
> [    0.000000] x8 : ffffffffff5fe000 x7 : 0000000000000000 x6 : 0000000000000000
> [    0.000000] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000
> [    0.000000] x2 : 0000000000000000 x1 : 0000000000000000 x0 : 0000000000000000
> [    0.000000] Call trace:
> [    0.000000]  arm64_rsi_is_protected_mmio+0xf0/0x110
> [    0.000000]  set_fixmap_io+0x8c/0xd0
> [    0.000000]  of_setup_earlycon+0xa0/0x294
> [    0.000000]  early_init_dt_scan_chosen_stdout+0x104/0x1dc
> [    0.000000]  acpi_boot_table_init+0x1a4/0x2d8
> [    0.000000]  setup_arch+0x240/0x610
> [    0.000000]  start_kernel+0x6c/0x708
> [    0.000000]  __primary_switched+0x80/0x88
> 

I have local changes like below to avoid the unexpected calltrace.

diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
index 9cb3353e5cbf..3d132d45fd83 100644
--- a/arch/arm64/kernel/rsi.c
+++ b/arch/arm64/kernel/rsi.c
@@ -100,14 +100,15 @@ bool arm64_rsi_is_protected_mmio(phys_addr_t base, size_t size)
         while (base < end) {
                 if (WARN_ON(rsi_ipa_state_get(base, end, &ripas, &top)))
                         break;
-               if (WARN_ON(top <= base))
+               if (WARN_ON(top && top <= base))
                         break;
                 if (ripas != RSI_RIPAS_IO)
                         break;
-               base = top;
+
+               base = top ? top : end;
         }
  
-       return (size && base >= end);
+       return base >= end;

Thanks,
Gavin