Re: [PATCH v6 06/21] arm64: Move VHE-specific SPE setup to mutate_to_vhe()
From: Will Deacon <will@kernel.org>
Date: 2021-02-03 21:14:25
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Hi Marc, On Mon, Feb 01, 2021 at 11:56:22AM +0000, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
There isn't much that a VHE kernel needs on top of whatever has been done for nVHE, so let's move the little we need to the VHE stub (the SPE setup), and drop the init_el2_state macro. No expected functional change. Signed-off-by: Marc Zyngier <maz@kernel.org> Acked-by: David Brazdil <redacted> Acked-by: Catalin Marinas <catalin.marinas@arm.com> --- arch/arm64/kernel/hyp-stub.S | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-)diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S index 373ed2213e1d..6b5c73cf9d52 100644 --- a/arch/arm64/kernel/hyp-stub.S +++ b/arch/arm64/kernel/hyp-stub.S@@ -92,9 +92,6 @@ SYM_CODE_START_LOCAL(mutate_to_vhe) msr hcr_el2, x0 isb - // Doesn't do much on VHE, but still, worth a shot - init_el2_state vhe - // Use the EL1 allocated stack, per-cpu offset mrs x0, sp_el1 mov sp, x0@@ -107,6 +104,31 @@ SYM_CODE_START_LOCAL(mutate_to_vhe) mrs_s x0, SYS_VBAR_EL12 msr vbar_el1, x0 + // Fixup SPE configuration, if supported... + mrs x1, id_aa64dfr0_el1 + ubfx x1, x1, #ID_AA64DFR0_PMSVER_SHIFT, #4 + mov x2, xzr + cbz x1, skip_spe + + // ... and not owned by EL3 + mrs_s x0, SYS_PMBIDR_EL1 + and x0, x0, #(1 << SYS_PMBIDR_EL1_P_SHIFT) + cbnz x0, skip_spe + + // Let the SPE driver in control of the sampling + mrs_s x0, SYS_PMSCR_EL1 + bic x0, x0, #(1 << SYS_PMSCR_EL2_PCT_SHIFT) + bic x0, x0, #(1 << SYS_PMSCR_EL2_PA_SHIFT) + msr_s SYS_PMSCR_EL1, x0
Why do we need to touch pmscr_el1 at all? The SPE driver should take care of that, no? If you drop the pmscr_el1 accesses, I think you can drop the pmbidr_el1 check as well. And actually, then why even check dfr0? Doing the bic for the mdcr_el1.e2pb bits is harmless.
+ mov x2, #MDCR_EL2_TPMS + +skip_spe: + // For VHE, use EL2 translation and disable access from EL1 + mrs x0, mdcr_el2 + bic x0, x0, #(MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT) + orr x0, x0, x2 + msr mdcr_el2, x0
Doesn't this undo the setting of mdcr_el2.hpmn if SPE is not present or unavailable? (This wouldn't be an issue if we removed the skip_spe paths altogether). Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel