On Wed, Mar 24, 2021 at 05:06:58PM +0000, Suzuki K Poulose wrote: > On 24/03/2021 16:30, Marc Zyngier wrote: > > On Wed, 24 Mar 2021 16:25:12 +0000, > > Suzuki K Poulose <suzuki.poul...@arm.com> wrote: > > > > > > On 24/03/2021 16:16, Marc Zyngier wrote: > > > > On Wed, 24 Mar 2021 15:51:14 +0000, > > > > Suzuki K Poulose <suzuki.poul...@arm.com> wrote: > > > > > > > > > > On 24/03/2021 13:49, Marc Zyngier wrote: > > > > > > On Wed, 24 Mar 2021 09:39:13 +0000, > > > > > > Suzuki K Poulose <suzuki.poul...@arm.com> wrote: > > > > > > > > > > > > > > On 23/03/2021 18:21, Catalin Marinas wrote: > > > > > > > > Hi Suzuki? > > > > > > > > > > > > > > > > On Tue, Mar 23, 2021 at 12:06:33PM +0000, Suzuki K Poulose > > > > > > > > wrote: > > > > > > > > > tsb csync synchronizes the trace operation of instructions. > > > > > > > > > The instruction is a nop when FEAT_TRF is not implemented. > > > > > > > > > > > > > > > > > > Cc: Mathieu Poirier <mathieu.poir...@linaro.org> > > > > > > > > > Cc: Mike Leach <mike.le...@linaro.org> > > > > > > > > > Cc: Catalin Marinas <catalin.mari...@arm.com> > > > > > > > > > Cc: Will Deacon <will.dea...@arm.com> > > > > > > > > > Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com> > > > > > > > > > > > > > > > > How do you plan to merge these patches? If they go via the > > > > > > > > coresight > > > > > > > > tree: > > > > > > > > > > > > > > > > > > > > > > Ideally all of this should go via the CoreSight tree to have the > > > > > > > dependencies solved at one place. But there are some issues : > > > > > > > > > > > > > > If this makes to 5.13 queue for CoreSight, > > > > > > > > > > > > > > 1) CoreSight next is based on rc2 at the moment and we have fixes > > > > > > > gone > > > > > > > into rc3 and later, which this series will depend on. (We could > > > > > > > move > > > > > > > the next tree forward to a later rc to solve this). > > > > > > > > > > > > > > 2) There could be conflicts with the kvmarm tree for the KVM host > > > > > > > changes (That has dependency on the TRBE definitions patch). > > > > > > > > > > > > > > If it doesn't make to 5.13 queue, it would be good to have this > > > > > > > patch, > > > > > > > the TRBE defintions and the KVM host patches queued for 5.13 (not > > > > > > > sure > > > > > > > if this is acceptable) and we could rebase the CoreSight changes > > > > > > > on 5.13 > > > > > > > and push it to next release. > > > > > > > > > > > > > > I am open for other suggestions. > > > > > > > > > > > > > > Marc, Mathieu, > > > > > > > > > > > > > > Thoughts ? > > > > > > > > > > > > I was planning to take the first two patches in 5.12 as fixes (they > > > > > > are queued already, and would hopefully land in -rc5). If that > > > > > > doesn't > > > > > > fit with the plan, please let me know ASAP. > > > > > > > > > > Marc, > > > > > > > > > > I think it would be better to hold on pushing those patches until we > > > > > have a clarity on how things will go. > > > > > > > > OK. I thought there was a need for these patches to prevent guest > > > > access to the v8.4 self hosted tracing feature that went in 5.12 > > > > though[1]... Did I get it wrong? > > > > > > Yes, that is correct. The guest could access the Trace Filter Control > > > register and fiddle with the host settings, without this patch. > > > e.g, it could disable tracing at EL0/EL1, without the host being > > > aware on nVHE host. > > > > OK, so we definitely do need these patches, don't we? Both? Just one? > > Please have a look at kvmarm/fixes and tell me what I must keep. > > Both of them are fixes. > > commit "KVM: arm64: Disable guest access to trace filter controls" > - This fixes guest fiddling with the trace filter control as described > above. > > commit "KVM: arm64: Hide system instruction access to Trace registers" > - Fixes the Hypervisor to advertise what it doesn't support. i.e > stop advertising trace system instruction access to a guest. > Otherwise a guest which trusts the ID registers > (ID_AA64DFR0_EL1.TRACEVER == 1) can crash while trying to access the > trace register as we trap the accesses (CPTR_EL2.TTA == 1). On Linux, > the ETM drivers need a DT explicitly advertising the support. So, > this is not immediately impacted. And this fix goes a long way back > in the history, when the CPTR_EL2.TTA was added. > > Now, the reason for asking you to hold on is the way this could create > conflicts in merging the rest of the series.
The way we normally work around this is to either rebase your series on top of -rc5 when the fixes go in or, if you want an earlier -rc base, Marc can put them on a stable branch somewhere that you can use. In the worst case you can merge the patches twice but that's rarely needed. -- Catalin