| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <8ba4d3dd-6ab2-49e3-9d25-d742e4958afc@arm.com>
Date: Fri, 5 Jan 2024 09:50:00 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: James Clark <james.clark@....com>, coresight@...ts.linaro.org,
linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev,
broonie@...nel.org, maz@...nel.org, acme@...nel.org
Cc: Oliver Upton <oliver.upton@...ux.dev>, James Morse <james.morse@....com>,
Zenghui Yu <yuzenghui@...wei.com>, Catalin Marinas
<catalin.marinas@....com>, Will Deacon <will@...nel.org>,
Mike Leach <mike.leach@...aro.org>, Leo Yan <leo.yan@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Anshuman Khandual <anshuman.khandual@....com>, Rob Herring
<robh@...nel.org>, Miguel Luis <miguel.luis@...cle.com>,
Jintack Lim <jintack.lim@...aro.org>, Ard Biesheuvel <ardb@...nel.org>,
Mark Rutland <mark.rutland@....com>, Helge Deller <deller@....de>,
Arnd Bergmann <arnd@...db.de>, Kalesh Singh <kaleshsingh@...gle.com>,
Quentin Perret <qperret@...gle.com>,
Vincent Donnefort <vdonnefort@...gle.com>, Fuad Tabba <tabba@...gle.com>,
Akihiko Odaki <akihiko.odaki@...nix.com>, Joey Gouly <joey.gouly@....com>,
Jing Zhang <jingzhangos@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/7] arm64: KVM: Write TRFCR value on guest switch with
nVHE
On 04/01/2024 16:27, James Clark wrote:
> The guest value for TRFCR requested by the Coresight driver is saved in
> kvm_host_global_state. On guest switch this value needs to be written to
> the register. Currently TRFCR is only modified when we want to disable
> trace completely in guests due to an issue with TRBE. Expand the
> __debug_save_trace() function to always write to the register if a
> different value for guests is required, but also keep the existing TRBE
> disable behavior if that's required.
>
> The TRFCR restore function remains functionally the same, except a value
> of 0 doesn't mean "don't restore" anymore. Now that we save both guest
> and host values the register is restored any time the guest and host
> values differ.
>
> Signed-off-by: James Clark <james.clark@....com>
> ---
> arch/arm64/kvm/hyp/nvhe/debug-sr.c | 55 ++++++++++++++++++------------
> 1 file changed, 34 insertions(+), 21 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
> index 4558c02eb352..7fd876d4f034 100644
> --- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
> +++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
> @@ -51,32 +51,45 @@ static void __debug_restore_spe(u64 pmscr_el1)
> write_sysreg_s(pmscr_el1, SYS_PMSCR_EL1);
> }
>
> -static void __debug_save_trace(u64 *trfcr_el1)
> +/*
> + * Save TRFCR and disable trace completely if TRBE is being used, otherwise
> + * apply required guest TRFCR value.
> + */
> +static void __debug_save_trace(struct kvm_vcpu *vcpu)
> {
> - *trfcr_el1 = 0;
> + u64 host_trfcr_el1 = read_sysreg_s(SYS_TRFCR_EL1);
> + u64 guest_trfcr_el1;
> +
> + vcpu->arch.host_debug_state.trfcr_el1 = host_trfcr_el1;
>
> /* Check if the TRBE is enabled */
> - if (!(read_sysreg_s(SYS_TRBLIMITR_EL1) & TRBLIMITR_EL1_E))
> - 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();
> + if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRBE) &&
> + (read_sysreg_s(SYS_TRBLIMITR_EL1) & TRBLIMITR_EL1_E)) {
> + /*
> + * 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.
> + */
> + write_sysreg_s(0, SYS_TRFCR_EL1);
> + isb();
> + /* Drain the trace buffer to memory */
> + tsb_csync();
> + } else {
> + /*
> + * Not using TRBE, so guest trace works. Apply the guest filters
> + * provided by the Coresight driver, if different.
> + */
> + guest_trfcr_el1 = kvm_host_global_state[vcpu->cpu].guest_trfcr_el1;
> + if (host_trfcr_el1 != guest_trfcr_el1)
> + write_sysreg_s(guest_trfcr_el1, SYS_TRFCR_EL1);
> + }
> }
>
> static void __debug_restore_trace(u64 trfcr_el1)
> {
> - if (!trfcr_el1)
> - return;
> -
> /* Restore trace filter controls */
> - write_sysreg_s(trfcr_el1, SYS_TRFCR_EL1);
> + if (trfcr_el1 != read_sysreg_s(SYS_TRFCR_EL1))
> + write_sysreg_s(trfcr_el1, SYS_TRFCR_EL1);
Could we not write it unconditionally here ? In the saving step, we have
to save the host setting. But while restoring, we could skip the check.
A read and write is probably the same cost, as the value is implicitly
synchronized by a later ISB.
Eitherways,
Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
> }
>
> void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
> @@ -85,8 +98,8 @@ void __debug_save_host_buffers_nvhe(struct kvm_vcpu *vcpu)
> if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_SPE))
> __debug_save_spe(&vcpu->arch.host_debug_state.pmscr_el1);
> /* Disable and flush Self-Hosted Trace generation */
> - if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRBE))
> - __debug_save_trace(&vcpu->arch.host_debug_state.trfcr_el1);
> + if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRFCR))
> + __debug_save_trace(vcpu);
> }
>
> void __debug_switch_to_guest(struct kvm_vcpu *vcpu)
> @@ -98,7 +111,7 @@ void __debug_restore_host_buffers_nvhe(struct kvm_vcpu *vcpu)
> {
> if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_SPE))
> __debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1);
> - if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRBE))
> + if (vcpu_get_flag(vcpu, DEBUG_STATE_SAVE_TRFCR))
> __debug_restore_trace(vcpu->arch.host_debug_state.trfcr_el1);
> }
>
Powered by blists - more mailing lists