From: Andrew Jones <ajones@ventanamicro.com>
To: Atish Patra <atishp@atishpatra.org>
Cc: Atish Patra <atishp@rivosinc.com>,
linux-kernel@vger.kernel.org, Albert Ou <aou@eecs.berkeley.edu>,
Anup Patel <anup@brainfault.org>, Guo Ren <guoren@kernel.org>,
kvm-riscv@lists.infradead.org, kvm@vger.kernel.org,
linux-riscv@lists.infradead.org,
Mark Rutland <mark.rutland@arm.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Will Deacon <will@kernel.org>
Subject: Re: [RFC 5/9] RISC-V: KVM: Add skeleton support for perf
Date: Thu, 24 Nov 2022 11:55:09 +0100 [thread overview]
Message-ID: <20221124105509.3kwnardcxvbbkf67@kamzik> (raw)
In-Reply-To: <CAOnJCULUH09HPZL6Ks-xUsiDLQPR6xOv2g+ic9Gd3uwea6hCyQ@mail.gmail.com>
On Thu, Nov 24, 2022 at 01:04:15AM -0800, Atish Patra wrote:
> On Wed, Nov 23, 2022 at 5:36 AM Andrew Jones <ajones@ventanamicro.com> wrote:
> >
> > ...
> > > > > > - csr_write(CSR_HCOUNTEREN, -1UL);
> > > > > > + /* VS should access only TM bit. Everything else should trap */
> > > > > > + csr_write(CSR_HCOUNTEREN, 0x02);
> > > > >
> > > > > This looks like something that should be broken out into a separate patch
> > > > > with a description of what happens now when guests try to access the newly
> > > > > trapping counter registers. We should probably also create a TM define.
> > > > >
> > > >
> > > > Done.
> > > >
> > >
> > > As we allow cycles & instret for host user space now [1], should we do the same
> > > for guests as well ? I would prefer not to but same user space
> > > software will start to break
> > > they will run inside a guest.
> > >
> > > https://lore.kernel.org/all/20220928131807.30386-1-palmer@rivosinc.com/
> > >
> >
> > Yeah, it seems like we should either forbid access to unprivileged users
> > or ensure the numbers include some random noise. For guests, a privileged
> > KVM userspace should need to explicitly request access for them, ensuring
> > that the creation of privileged guests is done by conscious choice.
> >
>
> If I understand you correctly, you are suggesting we only enable TM
> bit in hcounteren ?
Yeah, and also that I think it'd be nice to revisit this for userspace.
> We also need a mechanism to enable the hcounteren bits from KVM guest userspace.
>
> I can think of the following approaches.
>
> 1. The CYCLE, INSTRET enabling can also be via one reg interface.
> 2. We can enable it during first virtual instruction trap if these
> bits in guest scounteren
> are enabled.
Those sound good to me.
Thanks,
drew
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next prev parent reply other threads:[~2022-11-24 10:55 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-18 17:01 [RFC 0/9] KVM perf support Atish Patra
2022-07-18 17:01 ` [RFC 1/9] RISC-V: Define a helper function to probe number of hardware counters Atish Patra
2022-11-01 12:30 ` Andrew Jones
2022-11-21 23:50 ` Atish Patra
2022-07-18 17:01 ` [RFC 2/9] RISC-V: Define a helper function to return counter width Atish Patra
2022-07-18 17:01 ` [RFC 3/9] RISC-V: KVM: Define a probe function for SBI extension data structures Atish Patra
2022-11-01 15:32 ` Andrew Jones
2022-07-18 17:02 ` [RFC 4/9] RISC-V: KVM: Improve privilege mode filtering for perf Atish Patra
2022-11-01 12:51 ` Andrew Jones
2022-11-09 13:42 ` Sergey Matyukevich
2022-11-22 0:21 ` Atish Patra
2022-07-18 17:02 ` [RFC 5/9] RISC-V: KVM: Add skeleton support " Atish Patra
2022-11-01 14:13 ` Andrew Jones
2022-11-23 0:46 ` Atish Patra
2022-11-23 1:34 ` Atish Patra
2022-11-23 13:36 ` Andrew Jones
2022-11-24 9:04 ` Atish Patra
2022-11-24 10:55 ` Andrew Jones [this message]
2022-11-23 13:11 ` Andrew Jones
2022-11-24 9:09 ` Atish Patra
2022-11-24 11:14 ` Andrew Jones
2022-07-18 17:02 ` [RFC 6/9] RISC-V: KVM: Add SBI PMU extension support Atish Patra
2022-11-01 14:26 ` Andrew Jones
2022-11-22 23:08 ` Atish Patra
2022-11-23 13:58 ` Andrew Jones
2022-11-24 10:18 ` Atish Patra
2022-11-24 10:50 ` Andrew Jones
2022-11-24 12:59 ` Anup Patel
2022-11-28 21:00 ` Atish Patra
2022-07-18 17:02 ` [RFC 7/9] RISC-V: KVM: Implement trap & emulate for hpmcounters Atish Patra
2022-11-01 14:35 ` Andrew Jones
2022-11-22 23:11 ` Atish Patra
2022-07-18 17:02 ` [RFC 8/9] RISC-V: KVM: Implement perf support Atish Patra
2022-09-20 2:24 ` Eric Lin
2022-09-23 21:04 ` Atish Patra
2022-11-01 15:31 ` Andrew Jones
2022-11-23 0:45 ` Atish Patra
2022-11-23 14:22 ` Andrew Jones
2022-12-02 9:08 ` Atish Patra
2022-12-02 11:37 ` Andrew Jones
2022-12-07 8:49 ` Atish Patra
2022-12-02 17:09 ` Sean Christopherson
2022-12-07 8:06 ` Atish Patra
2022-12-07 16:31 ` Sean Christopherson
2022-12-08 1:11 ` Atish Patra
2022-07-18 17:02 ` [RFC 9/9] RISC-V: KVM: Implement firmware events Atish Patra
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