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SubjectRe: [PATCH v2] ACPI: OSL: Fix the memory mapping of an ACPI GAS that addresses a data structure
On Sun, May 22, 2022 at 11:44 PM <james.liu@hpe.com> wrote:
>
> From: James Liu <james.liu@hpe.com>
>
> Modify acpi_os_map_generic_address() & acpi_os_unmap_generic_address()
> to correctly handle cases that a GAS table (i.e., Table 5.1, ACPI 6.4)
> is used to address a data structure; in the case, the GAS has the field
> of "Register Bit Width" equal to 0.
>
> For example, "Injection Instruction Entry" (Table 18.25, ACPI 6.4) has
> a RegisterRegion field that is a GAS that points to a data structure
> SET_ERROR_TYPE_WITH_ADDRESS (Table 18.30), which is required when using
> EINJ (Error Injection module).
>
> This fix preserves a fairly sufficient memory space (i.e. page size) to

The hard-coded PAGE_SIZE allocation size is kind of a concern, because
the spec doesn't seem to limit the size of the structure pointed to by
the GAS to a page.

Also it is not clear from the spec that the RegisterRegion field in
Table 18.25 points to a structure. On the contrary, Section 18.6.2
says that it points to a register.

In any case, I don't think it is OK to use
acpi_os_map_generic_address() to map an address from a GAS pointing to
a data structure. acpi_os_map_memory() appears to be the right
interface to map such memory regions.

> store the data structure to prevent EINJ module from loading failure if
> platform firmware can correctly support Injection Instruction Entry in
> an EINJ table.
>
> Signed-off-by: James Liu <james.liu@hpe.com>
> ---
> drivers/acpi/osl.c | 27 +++++++++++++++++++++++----
> 1 file changed, 23 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c
> index 45c5c0e45..99f987c8c 100644
> --- a/drivers/acpi/osl.c
> +++ b/drivers/acpi/osl.c
> @@ -452,14 +452,20 @@ EXPORT_SYMBOL_GPL(acpi_os_unmap_memory);
>
> void __iomem *acpi_os_map_generic_address(struct acpi_generic_address *gas)
> {
> - u64 addr;
> + u64 addr = 0;
>
> if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
> return NULL;
>
> + /* Handle a case that GAS is used to address an ACPI data structure */
> + if (!gas->bit_width) {
> + pr_info("An ACPI data structure at 0x%llx is mapped\n", addr);
> + return acpi_os_map_iomem(addr, PAGE_SIZE);
> + }
> +
> /* Handle possible alignment issues */
> memcpy(&addr, &gas->address, sizeof(addr));
> - if (!addr || !gas->bit_width)
> + if (!addr)
> return NULL;
>
> return acpi_os_map_iomem(addr, gas->bit_width / 8);
> @@ -468,15 +474,28 @@ EXPORT_SYMBOL(acpi_os_map_generic_address);
>
> void acpi_os_unmap_generic_address(struct acpi_generic_address *gas)
> {
> - u64 addr;
> + u64 addr = 0;
> struct acpi_ioremap *map;
>
> if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY)
> return;
>
> + /* Handle a case that GAS is used to address an ACPI data structure */
> + if (!gas->bit_width) {
> + pr_info("An ACPI data structure at 0x%llx is unmapped\n", addr);
> + mutex_lock(&acpi_ioremap_lock);
> + map = acpi_map_lookup(addr, PAGE_SIZE);
> + if (!map) {
> + mutex_unlock(&acpi_ioremap_lock);
> + return;
> + }
> + acpi_os_drop_map_ref(map);
> + mutex_unlock(&acpi_ioremap_lock);
> + }
> +
> /* Handle possible alignment issues */
> memcpy(&addr, &gas->address, sizeof(addr));
> - if (!addr || !gas->bit_width)
> + if (!addr)
> return;
>
> mutex_lock(&acpi_ioremap_lock);
> --
> 2.25.1
>

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