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Date: Tue, 16 Mar 2021 11:49:24 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
mike.leach@...aro.org, anshuman.khandual@....com,
leo.yan@...aro.org, Will Deacon <will@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Marc Zyngier <maz@...nel.org>,
Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v4 08/19] arm64: kvm: Enable access to TRBE support for
host
On Thu, Feb 25, 2021 at 07:35:32PM +0000, Suzuki K Poulose wrote:
> For a nvhe host, the EL2 must allow the EL1&0 translation
> regime for TraceBuffer (MDCR_EL2.E2TB == 0b11). This must
> be saved/restored over a trip to the guest. Also, before
> entering the guest, we must flush any trace data if the
> TRBE was enabled. And we must prohibit the generation
> of trace while we are in EL1 by clearing the TRFCR_EL1.
>
> For vhe, the EL2 must prevent the EL1 access to the Trace
> Buffer.
>
> Cc: Will Deacon <will@...nel.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Marc Zyngier <maz@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> cc: Anshuman Khandual <anshuman.khandual@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> Changes
> - Rebased to linux-next.
> - Re-enable TRBE access on host restore.
> - For nvhe, flush the trace and prohibit the
> trace while we are at guest.
> ---
> arch/arm64/include/asm/el2_setup.h | 13 +++++++++
> arch/arm64/include/asm/kvm_arm.h | 2 ++
> arch/arm64/include/asm/kvm_host.h | 2 ++
> arch/arm64/kernel/hyp-stub.S | 3 ++-
> arch/arm64/kvm/debug.c | 6 ++---
> arch/arm64/kvm/hyp/nvhe/debug-sr.c | 42 ++++++++++++++++++++++++++++++
> arch/arm64/kvm/hyp/nvhe/switch.c | 1 +
> 7 files changed, 65 insertions(+), 4 deletions(-)
>
Acked-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> diff --git a/arch/arm64/include/asm/el2_setup.h b/arch/arm64/include/asm/el2_setup.h
> index d77d358f9395..bda918948471 100644
> --- a/arch/arm64/include/asm/el2_setup.h
> +++ b/arch/arm64/include/asm/el2_setup.h
> @@ -65,6 +65,19 @@
> // use EL1&0 translation.
>
> .Lskip_spe_\@:
> + /* Trace buffer */
> + ubfx x0, x1, #ID_AA64DFR0_TRBE_SHIFT, #4
> + cbz x0, .Lskip_trace_\@ // Skip if TraceBuffer is not present
> +
> + mrs_s x0, SYS_TRBIDR_EL1
> + and x0, x0, TRBIDR_PROG
> + cbnz x0, .Lskip_trace_\@ // If TRBE is available at EL2
> +
> + mov x0, #(MDCR_EL2_E2TB_MASK << MDCR_EL2_E2TB_SHIFT)
> + orr x2, x2, x0 // allow the EL1&0 translation
> + // to own it.
> +
> +.Lskip_trace_\@:
> msr mdcr_el2, x2 // Configure debug traps
> .endm
>
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 94d4025acc0b..692c9049befa 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -278,6 +278,8 @@
> #define CPTR_EL2_DEFAULT CPTR_EL2_RES1
>
> /* Hyp Debug Configuration Register bits */
> +#define MDCR_EL2_E2TB_MASK (UL(0x3))
> +#define MDCR_EL2_E2TB_SHIFT (UL(24))
> #define MDCR_EL2_TTRF (1 << 19)
> #define MDCR_EL2_TPMS (1 << 14)
> #define MDCR_EL2_E2PB_MASK (UL(0x3))
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3d10e6527f7d..80d0a1a82a4c 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -315,6 +315,8 @@ struct kvm_vcpu_arch {
> struct kvm_guest_debug_arch regs;
> /* Statistical profiling extension */
> u64 pmscr_el1;
> + /* Self-hosted trace */
> + u64 trfcr_el1;
> } host_debug_state;
>
> /* VGIC state */
> diff --git a/arch/arm64/kernel/hyp-stub.S b/arch/arm64/kernel/hyp-stub.S
> index 678cd2c618ee..ba84502b582a 100644
> --- a/arch/arm64/kernel/hyp-stub.S
> +++ b/arch/arm64/kernel/hyp-stub.S
> @@ -115,9 +115,10 @@ SYM_CODE_START_LOCAL(mutate_to_vhe)
> mrs_s x0, SYS_VBAR_EL12
> msr vbar_el1, x0
>
> - // Use EL2 translations for SPE and disable access from EL1
> + // Use EL2 translations for SPE & TRBE and disable access from EL1
> mrs x0, mdcr_el2
> bic x0, x0, #(MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT)
> + bic x0, x0, #(MDCR_EL2_E2TB_MASK << MDCR_EL2_E2TB_SHIFT)
> msr mdcr_el2, x0
>
> // Transfer the MM state from EL1 to EL2
> diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
> index dbc890511631..7b16f42d39f4 100644
> --- a/arch/arm64/kvm/debug.c
> +++ b/arch/arm64/kvm/debug.c
> @@ -89,7 +89,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
> * - Debug ROM Address (MDCR_EL2_TDRA)
> * - OS related registers (MDCR_EL2_TDOSA)
> * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB)
> - * - Self-hosted Trace Filter controls (MDCR_EL2_TTRF)
> + * - Self-hosted Trace (MDCR_EL2_TTRF/MDCR_EL2_E2TB)
> *
> * Additionally, KVM only traps guest accesses to the debug registers if
> * the guest is not actively using them (see the KVM_ARM64_DEBUG_DIRTY
> @@ -107,8 +107,8 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
> trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
>
> /*
> - * This also clears MDCR_EL2_E2PB_MASK to disable guest access
> - * to the profiling buffer.
> + * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK
> + * to disable guest access to the profiling and trace buffers
> */
> vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
> vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
> diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
> index f401724f12ef..9499e18dd28f 100644
> --- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
> +++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
> @@ -58,10 +58,51 @@ static void __debug_restore_spe(u64 pmscr_el1)
> write_sysreg_s(pmscr_el1, SYS_PMSCR_EL1);
> }
>
> +static void __debug_save_trace(u64 *trfcr_el1)
> +{
> +
> + *trfcr_el1 = 0;
> +
> + /* Check if we have TRBE */
> + if (!cpuid_feature_extract_unsigned_field(read_sysreg(id_aa64dfr0_el1),
> + ID_AA64DFR0_TRBE_SHIFT))
> + return;
> +
> + /* Check we can access the TRBE */
> + if ((read_sysreg_s(SYS_TRBIDR_EL1) & TRBIDR_PROG))
> + return;
> +
> + /* Check if the TRBE is enabled */
> + if (!(read_sysreg_s(SYS_TRBLIMITR_EL1) & TRBLIMITR_ENABLE))
> + return;
> + /*
> + * Prohibit trace generation while we are in guest.
> + * Since access to TRFCR_EL1 is trapped, the guest can't
> + * modify the filtering set by the host.
> + */
> + *trfcr_el1 = read_sysreg_s(SYS_TRFCR_EL1);
> + write_sysreg_s(0, SYS_TRFCR_EL1);
> + isb();
> + /* Drain the trace buffer to memory */
> + tsb_csync();
> + dsb(nsh);
> +}
> +
> +static void __debug_restore_trace(u64 trfcr_el1)
> +{
> + if (!trfcr_el1)
> + return;
> +
> + /* Restore trace filter controls */
> + write_sysreg_s(trfcr_el1, SYS_TRFCR_EL1);
> +}
> +
> void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
> {
> /* Disable and flush SPE data generation */
> __debug_save_spe(&vcpu->arch.host_debug_state.pmscr_el1);
> + /* Disable and flush Self-Hosted Trace generation */
> + __debug_save_trace(&vcpu->arch.host_debug_state.trfcr_el1);
> }
>
> void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
> @@ -72,6 +113,7 @@ void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
> void __debug_restore_host_buffers_nvhe(struct kvm_vcpu *vcpu)
> {
> __debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1);
> + __debug_restore_trace(vcpu->arch.host_debug_state.trfcr_el1);
> }
>
> void __debug_switch_to_host(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
> index 10eed66136a0..d6ea5c8b5551 100644
> --- a/arch/arm64/kvm/hyp/nvhe/switch.c
> +++ b/arch/arm64/kvm/hyp/nvhe/switch.c
> @@ -95,6 +95,7 @@ static void __deactivate_traps(struct kvm_vcpu *vcpu)
>
> mdcr_el2 &= MDCR_EL2_HPMN_MASK;
> mdcr_el2 |= MDCR_EL2_E2PB_MASK << MDCR_EL2_E2PB_SHIFT;
> + mdcr_el2 |= MDCR_EL2_E2TB_MASK << MDCR_EL2_E2TB_SHIFT;
>
> write_sysreg(mdcr_el2, mdcr_el2);
> if (is_protected_kvm_enabled())
> --
> 2.24.1
>
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