Messages in this thread Patch in this message | | | Date | Mon, 26 Feb 2024 18:26:53 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH v6 7/8] arm64: KVM: Write TRFCR value on guest switch with nVHE |
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On Mon, 26 Feb 2024 11:30:35 +0000, James Clark <james.clark@arm.com> 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 <suzuki.poulose@arm.com> > Signed-off-by: James Clark <james.clark@arm.com> > --- > 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.
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