Messages in this thread Patch in this message |  | | Date | Thu, 04 Feb 2021 09:30:08 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH v6 06/21] arm64: Move VHE-specific SPE setup to mutate_to_vhe() |
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Hi Will,
On 2021-02-03 21:13, Will Deacon wrote: > Hi Marc, > > On Mon, Feb 01, 2021 at 11:56:22AM +0000, Marc Zyngier wrote: >> 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 <dbrazdil@google.com> >> 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.
That's definitely a brain fart, and is what we need on the nVHE path, not here. Doing the same thing twice isn't exactly helpful.
> 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).
I don't think it does. We only clear the E2PB bits (harmless, as you point out above), and OR something that is either 0 (no SPE) or MDCR_EL2_TPMS. In any case, the HPMN bits are preserved (having been set during the nVHE setup).
I think the following patch addresses the above issue, which I'll squash with the original patch. Please shout if I missed anything.
Thanks,
M.
diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S index aa7e8d592295..3e08dcc924b5 100644 --- a/arch/arm64/kernel/hyp-stub.S +++ b/arch/arm64/kernel/hyp-stub.S @@ -115,29 +115,9 @@ 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 - mov x2, #MDCR_EL2_TPMS - -skip_spe: - // For VHE, use EL2 translation and disable access from EL1 + // Use EL2 translations for SPE 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
// Transfer the MM state from EL1 to EL2 -- Jazz is not dead. It just smells funny...
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