| f396aec8 | 09-Sep-2025 |
Arvind Ram Prakash <arvind.ramprakash@arm.com> |
feat(cpufeat): add support for FEAT_IDTE3
This patch adds support for FEAT_IDTE3, which introduces support
for handling the trapping of Group 3 and Group 5 (only GMID_EL1)
registers to EL3 (unless t
feat(cpufeat): add support for FEAT_IDTE3
This patch adds support for FEAT_IDTE3, which introduces support
for handling the trapping of Group 3 and Group 5 (only GMID_EL1)
registers to EL3 (unless trapped to EL2). IDTE3 allows EL3 to
modify the view of ID registers for lower ELs, and this capability
is used to disable fields of ID registers tied to disabled features.
The ID registers are initially read as-is and stored in context.
Then, based on the feature enablement status for each world, if a
particular feature is disabled, its corresponding field in the
cached ID register is set to Res0. When lower ELs attempt to read
an ID register, the cached ID register value is returned. This
allows EL3 to prevent lower ELs from accessing feature-specific
system registers that are disabled in EL3, even though the hardware
implements them.
The emulated ID register values are stored primarily in per-world
context, except for certain debug-related ID registers such as
ID_AA64DFR0_EL1 and ID_AA64DFR1_EL1, which are stored in the
cpu_data and are unique to each PE. This is done to support feature
asymmetry that is commonly seen in debug features.
FEAT_IDTE3 traps all Group 3 ID registers in the range
op0 == 3, op1 == 0, CRn == 0, CRm == {2–7}, op2 == {0–7} and the
Group 5 GMID_EL1 register. However, only a handful of ID registers
contain fields used to detect features enabled in EL3. Hence, we
only cache those ID registers, while the rest are transparently
returned as is to the lower EL.
This patch updates the CREATE_FEATURE_FUNCS macro to generate
update_feat_xyz_idreg_field() functions that disable ID register
fields on a per-feature basis. The enabled_worlds scope is used to
disable ID register fields for security states where the feature is
not enabled.
This EXPERIMENTAL feature is controlled by the ENABLE_FEAT_IDTE3
build flag and is currently disabled by default.
Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: I5f998eeab81bb48c7595addc5595313a9ebb96d5
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| 51997e3d | 02-Apr-2025 |
Boyan Karatotev <boyan.karatotev@arm.com> |
perf(cpufeat): centralise PAuth key saving
prepare_el3_entry() is meant to be the one-stop shop for all the context
we must fiddle with to enter EL3 proper. However, PAuth is the one
exception, happ
perf(cpufeat): centralise PAuth key saving
prepare_el3_entry() is meant to be the one-stop shop for all the context
we must fiddle with to enter EL3 proper. However, PAuth is the one
exception, happening right after. Absorb it into prepare_el3_entry(),
handling the BL1/BL31 difference.
This is a good time to also move the key saving into the enable
function, also to centralise. With this it becomes apparent that saving
keys just before CPU_SUSPEND is redundant as they will be reinitialised
when the core wakes up.
Note that the key loading, now in save_gp_pmcr_pauth_regs, does not end
in an isb. The effects of the key change are not needed until the isb
in the caller, so this isb is not needed.
Change-Id: Idd286bea91140c106ab4c933c5c44b0bc2050ca2
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
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| f8138056 | 02-Apr-2025 |
Boyan Karatotev <boyan.karatotev@arm.com> |
refactor(cpufeat): convert FEAT_PAuth setup to C
An oversimplified view of FEAT_PAuth is that it's a symmetric encryption
of the LR. PAC instructions execute as NOPs until explicitly turned on.
So i
refactor(cpufeat): convert FEAT_PAuth setup to C
An oversimplified view of FEAT_PAuth is that it's a symmetric encryption
of the LR. PAC instructions execute as NOPs until explicitly turned on.
So in a function that turns PAuth on, the signing would have executed as
a NOP and the authentication will encrypt the address, leading to a
failure. That's why enablement is in assembly - we have full control of
when pointer authentications happen.
However, assembly is hard to read, is opaque to the compiler for
optimisations, and we need to call into C anyway for the platform hook
to get the key. So convert it to C. We can instruct the compiler to not
generate branch protection for the enable function only and as long as
the caller doesn't do branch protection (and all callers are entrypoints
written in assembly) everything will work.
Change-Id: I8917a26e1293033c910e3058664e3ca9207359b7
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
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| 0a580b51 | 15-Nov-2024 |
Boyan Karatotev <boyan.karatotev@arm.com> |
perf(cm): drop ZCR_EL3 saving and some ISBs and replace them with root context
SVE and SME aren't enabled symmetrically for all worlds, but EL3 needs
to context switch them nonetheless. Previously,
perf(cm): drop ZCR_EL3 saving and some ISBs and replace them with root context
SVE and SME aren't enabled symmetrically for all worlds, but EL3 needs
to context switch them nonetheless. Previously, this had to happen by
writing the enable bits just before reading/writing the relevant
context. But since the introduction of root context, this need not be
the case. We can have these enables always be present for EL3 and save
on some work (and ISBs!) on every context switch.
We can also hoist ZCR_EL3 to a never changing register, as we set its
value to be identical for every world, which happens to be the one we
want for EL3 too.
Change-Id: I3d950e72049a298008205ba32f230d5a5c02f8b0
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
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