Re: [PATCH v5 05/19] arm64: Detect if in a realm and set RIPAS RAM

[Shanker Donthineni <sdonthineni@nvidia.com>]

Hi Steven,

On 8/19/24 08:19, Steven Price wrote:
> External email: Use caution opening links or attachments
> 
> 
> From: Suzuki K Poulose <suzuki.poulose@arm.com>
> 
> Detect that the VM is a realm guest by the presence of the RSI
> interface.
> 
> If in a realm then all memory needs to be marked as RIPAS RAM initially,
> the loader may or may not have done this for us. To be sure iterate over
> all RAM and mark it as such. Any failure is fatal as that implies the
> RAM regions passed to Linux are incorrect - which would mean failing
> later when attempting to access non-existent RAM.
> 
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Co-developed-by: Steven Price <steven.price@arm.com>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> Changes since v4:
>   * Minor tidy ups.
> Changes since v3:
>   * Provide safe/unsafe versions for converting memory to protected,
>     using the safer version only for the early boot.
>   * Use the new psci_early_test_conduit() function to avoid calling an
>     SMC if EL3 is not present (or not configured to handle an SMC).
> Changes since v2:
>   * Use DECLARE_STATIC_KEY_FALSE rather than "extern struct
>     static_key_false".
>   * Rename set_memory_range() to rsi_set_memory_range().
>   * Downgrade some BUG()s to WARN()s and handle the condition by
>     propagating up the stack. Comment the remaining case that ends in a
>     BUG() to explain why.
>   * Rely on the return from rsi_request_version() rather than checking
>     the version the RMM claims to support.
>   * Rename the generic sounding arm64_setup_memory() to
>     arm64_rsi_setup_memory() and move the call site to setup_arch().
> ---
>   arch/arm64/include/asm/rsi.h | 65 ++++++++++++++++++++++++++++++
>   arch/arm64/kernel/Makefile   |  3 +-
>   arch/arm64/kernel/rsi.c      | 78 ++++++++++++++++++++++++++++++++++++
>   arch/arm64/kernel/setup.c    |  8 ++++
>   4 files changed, 153 insertions(+), 1 deletion(-)
>   create mode 100644 arch/arm64/include/asm/rsi.h
>   create mode 100644 arch/arm64/kernel/rsi.c
> 
> diff --git a/arch/arm64/include/asm/rsi.h b/arch/arm64/include/asm/rsi.h
> new file mode 100644
> index 000000000000..2bc013badbc3
> --- /dev/null
> +++ b/arch/arm64/include/asm/rsi.h
> @@ -0,0 +1,65 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2024 ARM Ltd.
> + */
> +
> +#ifndef __ASM_RSI_H_
> +#define __ASM_RSI_H_
> +
> +#include <linux/jump_label.h>
> +#include <asm/rsi_cmds.h>
> +
> +DECLARE_STATIC_KEY_FALSE(rsi_present);
> +
> +void __init arm64_rsi_init(void);
> +void __init arm64_rsi_setup_memory(void);
> +static inline bool is_realm_world(void)
> +{
> +       return static_branch_unlikely(&rsi_present);
> +}
> +
> +static inline int rsi_set_memory_range(phys_addr_t start, phys_addr_t end,
> +                                      enum ripas state, unsigned long flags)
> +{
> +       unsigned long ret;
> +       phys_addr_t top;
> +
> +       while (start != end) {
> +               ret = rsi_set_addr_range_state(start, end, state, flags, &top);
> +               if (WARN_ON(ret || top < start || top > end))
> +                       return -EINVAL;
> +               start = top;
> +       }
> +
> +       return 0;
> +}
> +
> +/*
> + * Convert the specified range to RAM. Do not use this if you rely on the
> + * contents of a page that may already be in RAM state.
> + */
> +static inline int rsi_set_memory_range_protected(phys_addr_t start,
> +                                                phys_addr_t end)
> +{
> +       return rsi_set_memory_range(start, end, RSI_RIPAS_RAM,
> +                                   RSI_CHANGE_DESTROYED);
> +}
> +
> +/*
> + * Convert the specified range to RAM. Do not convert any pages that may have
> + * been DESTROYED, without our permission.
> + */
> +static inline int rsi_set_memory_range_protected_safe(phys_addr_t start,
> +                                                     phys_addr_t end)
> +{
> +       return rsi_set_memory_range(start, end, RSI_RIPAS_RAM,
> +                                   RSI_NO_CHANGE_DESTROYED);
> +}
> +
> +static inline int rsi_set_memory_range_shared(phys_addr_t start,
> +                                             phys_addr_t end)
> +{
> +       return rsi_set_memory_range(start, end, RSI_RIPAS_EMPTY,
> +                                   RSI_NO_CHANGE_DESTROYED);
> +}
> +#endif /* __ASM_RSI_H_ */
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 2b112f3b7510..71c29a2a2f19 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -33,7 +33,8 @@ obj-y                 := debug-monitors.o entry.o irq.o fpsimd.o              \
>                             return_address.o cpuinfo.o cpu_errata.o              \
>                             cpufeature.o alternative.o cacheinfo.o               \
>                             smp.o smp_spin_table.o topology.o smccc-call.o       \
> -                          syscall.o proton-pack.o idle.o patching.o pi/
> +                          syscall.o proton-pack.o idle.o patching.o pi/        \
> +                          rsi.o
> 
>   obj-$(CONFIG_COMPAT)                   += sys32.o signal32.o                   \
>                                             sys_compat.o
> diff --git a/arch/arm64/kernel/rsi.c b/arch/arm64/kernel/rsi.c
> new file mode 100644
> index 000000000000..128a9a05a96b
> --- /dev/null
> +++ b/arch/arm64/kernel/rsi.c
> @@ -0,0 +1,78 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2023 ARM Ltd.
> + */
> +
> +#include <linux/jump_label.h>
> +#include <linux/memblock.h>
> +#include <linux/psci.h>
> +#include <asm/rsi.h>
> +
> +DEFINE_STATIC_KEY_FALSE_RO(rsi_present);
> +EXPORT_SYMBOL(rsi_present);
> +
> +static bool rsi_version_matches(void)
> +{
> +       unsigned long ver_lower, ver_higher;
> +       unsigned long ret = rsi_request_version(RSI_ABI_VERSION,
> +                                               &ver_lower,
> +                                               &ver_higher);
> +
> +       if (ret == SMCCC_RET_NOT_SUPPORTED)
> +               return false;
> +
> +       if (ret != RSI_SUCCESS) {
> +               pr_err("RME: RMM doesn't support RSI version %lu.%lu. Supported range: %lu.%lu-%lu.%lu\n",
> +                      RSI_ABI_VERSION_MAJOR, RSI_ABI_VERSION_MINOR,
> +                      RSI_ABI_VERSION_GET_MAJOR(ver_lower),
> +                      RSI_ABI_VERSION_GET_MINOR(ver_lower),
> +                      RSI_ABI_VERSION_GET_MAJOR(ver_higher),
> +                      RSI_ABI_VERSION_GET_MINOR(ver_higher));
> +               return false;
> +       }
> +
> +       pr_info("RME: Using RSI version %lu.%lu\n",
> +               RSI_ABI_VERSION_GET_MAJOR(ver_lower),
> +               RSI_ABI_VERSION_GET_MINOR(ver_lower));
> +
> +       return true;
> +}
> +
> +void __init arm64_rsi_setup_memory(void)
> +{
> +       u64 i;
> +       phys_addr_t start, end;
> +
> +       if (!is_realm_world())
> +               return;
> +
> +       /*
> +        * Iterate over the available memory ranges and convert the state to
> +        * protected memory. We should take extra care to ensure that we DO NOT
> +        * permit any "DESTROYED" pages to be converted to "RAM".
> +        *
> +        * BUG_ON is used because if the attempt to switch the memory to
> +        * protected has failed here, then future accesses to the memory are
> +        * simply going to be reflected as a SEA (Synchronous External Abort)
> +        * which we can't handle.  Bailing out early prevents the guest limping
> +        * on and dying later.
> +        */
> +       for_each_mem_range(i, &start, &end) {
> +               BUG_ON(rsi_set_memory_range_protected_safe(start, end));
> +       }
> +}
> +
> +void __init arm64_rsi_init(void)
> +{
> +       /*
> +        * If PSCI isn't using SMC, RMM isn't present. Don't try to execute an
> +        * SMC as it could be UNDEFINED.
> +        */
> +       if (!psci_early_test_conduit(SMCCC_CONDUIT_SMC))
> +               return;
For ACPI-based kernel boot flow, control never reaches this point because the above
function does not check the PSCI conduit method when the kernel is booted via UEFI.

As a result, the boot process fails when using ACPI. It works fine with DTB based
boot.

> +       if (!rsi_version_matches())
> +               return;
> +
> +       static_branch_enable(&rsi_present);
> +}
> +
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index a096e2451044..143f87615af0 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -43,6 +43,7 @@
>   #include <asm/cpu_ops.h>
>   #include <asm/kasan.h>
>   #include <asm/numa.h>
> +#include <asm/rsi.h>
>   #include <asm/scs.h>
>   #include <asm/sections.h>
>   #include <asm/setup.h>
> @@ -293,6 +294,11 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
>           * cpufeature code and early parameters.
>           */
>          jump_label_init();
> +       /*
> +        * Init RSI before early param so that "earlycon" console uses the
> +        * shared alias when in a realm
> +        */
> +       arm64_rsi_init();
>          parse_early_param();
> 
>          dynamic_scs_init();
> @@ -328,6 +334,8 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
> 
>          arm64_memblock_init();
> 
> +       arm64_rsi_setup_memory();
> +
>          paging_init();
> 
>          acpi_table_upgrade();
> --
> 2.34.1
>