arm64: Add an override for ID_AA64SMFR0_EL1.FA64

Add a specific override for ID_AA64SMFR0_EL1.FA64, which
disables the full A64 streaming SVE mode.

Note that no alias is provided for this, as this is already
covered by arm64.nosme, and is only added as a debugging
facility.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220630160500.1536744-10-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
index d6b0a70..3dcc327 100644 (file)
--- a/arch/arm64/kernel/hyp-stub.S
+++ b/arch/arm64/kernel/hyp-stub.S
@@ -122,17 +122,18 @@ SYM_CODE_START_LOCAL(__finalise_el2)
        msr     sctlr_el2, x1
        isb
 
-       mov     x1, #0                          // SMCR controls
+       mov     x0, #0                          // SMCR controls
 
-       mrs_s   x2, SYS_ID_AA64SMFR0_EL1
-       ubfx    x2, x2, #ID_AA64SMFR0_FA64_SHIFT, #1 // Full FP in SM?
-       cbz     x2, .Lskip_sme_fa64
+       // Full FP in SM?
+       mrs_s   x1, SYS_ID_AA64SMFR0_EL1
+       __check_override id_aa64smfr0 ID_AA64SMFR0_FA64_SHIFT 1 .Linit_sme_fa64 .Lskip_sme_fa64
 
-       orr     x1, x1, SMCR_ELx_FA64_MASK
+.Linit_sme_fa64:
+       orr     x0, x0, SMCR_ELx_FA64_MASK
 .Lskip_sme_fa64:
 
-       orr     x1, x1, #SMCR_ELx_LEN_MASK      // Enable full SME vector
-       msr_s   SYS_SMCR_EL2, x1                // length for EL1.
+       orr     x0, x0, #SMCR_ELx_LEN_MASK      // Enable full SME vector
+       msr_s   SYS_SMCR_EL2, x0                // length for EL1.
 
        mrs_s   x1, SYS_SMIDR_EL1               // Priority mapping supported?
        ubfx    x1, x1, #SMIDR_EL1_SMPS_SHIFT, #1

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index 7cca826..aa2a53d 100644 (file)
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -127,6 +127,16 @@ static const struct ftr_set_desc isar2 __initconst = {
        },
 };
 
+static const struct ftr_set_desc smfr0 __initconst = {
+       .name           = "id_aa64smfr0",
+       .override       = &id_aa64smfr0_override,
+       .fields         = {
+               /* FA64 is a one bit field... :-/ */
+               { "fa64", ID_AA64SMFR0_FA64_SHIFT, 1, },
+               {}
+       },
+};
+
 extern struct arm64_ftr_override kaslr_feature_override;
 
 static const struct ftr_set_desc kaslr __initconst = {
@@ -146,6 +156,7 @@ static const struct ftr_set_desc * const regs[] __initconst = {
        &pfr1,
        &isar1,
        &isar2,
+       &smfr0,
        &kaslr,
 };