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Mon, 26 Feb 2024 18:26:53 +0000 Date: Mon, 26 Feb 2024 18:26:53 +0000 Message-ID: <868r372iaa.wl-maz@kernel.org> From: Marc Zyngier To: James Clark Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, suzuki.poulose@arm.com, acme@kernel.org, oliver.upton@linux.dev, broonie@kernel.org, James Morse , Zenghui Yu , Catalin Marinas , Will Deacon , Mike Leach , Alexander Shishkin , Anshuman Khandual , Miguel Luis , Joey Gouly , Ard Biesheuvel , Javier Martinez Canillas , Mark Rutland , Arnd Bergmann , Andrew Walbran , Vincent Donnefort , Ryan Roberts , Fuad Tabba , Jing Zhang , linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 7/8] arm64: KVM: Write TRFCR value on guest switch with nVHE In-Reply-To: <20240226113044.228403-8-james.clark@arm.com> References: <20240226113044.228403-1-james.clark@arm.com> <20240226113044.228403-8-james.clark@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: james.clark@arm.com, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, suzuki.poulose@arm.com, acme@kernel.org, oliver.upton@linux.dev, broonie@kernel.org, james.morse@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, mike.leach@linaro.org, alexander.shishkin@linux.intel.com, anshuman.khandual@arm.com, miguel.luis@oracle.com, joey.gouly@arm.com, ardb@kernel.org, javierm@redhat.com, mark.rutland@arm.com, arnd@arndb.de, qwandor@google.com, vdonnefort@google.com, ryan.roberts@arm.com, tabba@google.com, jingzhangos@google.com, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240226_102657_126430_15E93614 X-CRM114-Status: GOOD ( 29.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 26 Feb 2024 11:30:35 +0000, James Clark wrote: > > The guest value for TRFCR requested by the Coresight driver is saved in > kvm_guest_trfcr. 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. > > In pKVM, the kvm_guest_trfcr can't be read and the host isn't trusted, > so always disable trace. > > __debug_restore_trace() now has to restore unconditionally, because even > a value of 0 needs to be written to overwrite whatever was set for the > guest. > > Reviewed-by: Suzuki K Poulose > Signed-off-by: James Clark > --- > arch/arm64/kvm/hyp/nvhe/debug-sr.c | 53 +++++++++++++++++------------- > 1 file changed, 31 insertions(+), 22 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c > index 4558c02eb352..3adac2e01908 100644 > --- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c > +++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c > @@ -51,30 +51,39 @@ static void __debug_restore_spe(u64 pmscr_el1) > write_sysreg_s(pmscr_el1, SYS_PMSCR_EL1); > } > > -static void __debug_save_trace(u64 *trfcr_el1) > +static void __debug_save_trace(struct kvm_vcpu *vcpu) > { > - *trfcr_el1 = 0; > - > - /* 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(); > + u64 host_trfcr_el1 = read_sysreg_s(SYS_TRFCR_EL1); Ah, and on top of that, this is already broken with hVHE. I'll send a patch. M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel