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lib: sbi_domain: Allow MMIO access to non-MMIO ranges

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Currently, platforms do not provide complete memory region information
to OpenSBI. Generally, memory regions are only created for the few MMIO
devices that have M-mode drivers. As a result, most MMIO devices fall
inside the default S-mode RWX memory region, which does _not_ have the
MMIO flag set.

In fact, OpenSBI relies on certain S-mode MMIO devices being inside
non-MMIO memory regions. Both fdt_domain_based_fixup_one() and
mpxy_rpmi_sysmis_xfer() call sbi_domain_check_addr() with the MMIO flag
cleared, and that function currently requires an exact flag match. Those
access checks will thus erroneously fail if the platform creates memory
regions with the correct flags for these devices (or for a larger MMIO
region containing these devices).

We should not ignore the MMIO flag entirely, because
sbi_domain_check_addr() is also used to check the permissions of S-mode
shared memory buffers, and S-mode should not be using MMIO device
addresses as memory buffers. But when checking if S-mode is allowed to
do MMIO accesses, we need to recognize that MMIO devices appear in
memory regions both with and without the MMIO flag set.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Yu-Chien Peter Lin <peter.lin@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20251121193808.1528050-2-samuel.holland@sifive.com
Signed-off-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Samuel Holland
2025-11-21 11:37:51 -08:00
committed by Anup Patel
parent 126c9d34d2
commit 1f9677582a
1 changed files with 5 additions and 1 deletions
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6
lib/sbi/sbi_domain.c
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@@ -235,7 +235,11 @@ bool sbi_domain_check_addr(const struct sbi_domain *dom,
rstart + ((1UL << reg->order) - 1) : -1UL;
if (rstart <= addr && addr <= rend) {
rmmio = (rflags & SBI_DOMAIN_MEMREGION_MMIO) ? true : false;
if (mmio != rmmio)
/*
* MMIO devices may appear in regions without the flag set (such as the
* default region), but MMIO device regions should not be used as memory.
*/
if (!mmio && rmmio)
return false;
return ((rrwx & rwx) == rwx) ? true : false;
}