Re: [PATCH v3] target/riscv: update checks on writing pmpcfg for Smepmp

[Alistair Francis]

On Tue, Sep 19, 2023 at 3:08 PM Chang Alvin <vivahavey@gmail.com> wrote:
>
>  > -----Original Message-----
>
> > From: Alistair Francis <alistair23@gmail.com>
>
> > Sent: Tuesday, September 19, 2023 12:42 PM
>
> > To: Alvin Che-Chia Chang(張哲嘉) <alvinga@andestech.com>
>
> > Cc: qemu-riscv@nongnu.org; qemu-devel@nongnu.org;
>
> > alistair.francis@wdc.com; ajones@ventanamicro.com
>
> > Subject: Re: [PATCH v3] target/riscv: update checks on writing pmpcfg for
>
> > Smepmp to version 1.0
>
> >
>
> > On Fri, Sep 15, 2023 at 6:32 PM Alvin Chang <alvinga@andestech.com> wrote:
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> > >
>
> > > Current checks on writing pmpcfg for Smepmp follows Smepmp version
>
> > > 0.9.1. However, Smepmp specification has already been ratified, and
>
> > > there are some differences between version 0.9.1 and 1.0. In this
>
> > > commit we update the checks of writing pmpcfg to follow Smepmp version
>
> > > 1.0.
>
> > >
>
> > > When mseccfg.MML is set, the constraints to modify PMP rules are:
>
> > > 1. Locked rules cannot be removed or modified until a PMP reset, unless
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> > >    mseccfg.RLB is set.
>
> > > 2. From Smepmp specification version 1.0, chapter 2 section 4b:
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> > >    Adding a rule with executable privileges that either is M-mode-only
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> > >    or a locked Shared-Region is not possible and such pmpcfg writes are
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> > >    ignored, leaving pmpcfg unchanged.
>
> > >
>
> > > The commit transfers the value of pmpcfg into the index of the Smepmp
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> > > truth table, and checks the rules by aforementioned specification
>
> > > changes.
>
> > >
>
> > > Signed-off-by: Alvin Chang <alvinga@andestech.com>
>
> > > ---
>
> > > Changes from v2: Adopt switch case ranges and numerical order.
>
> > >
>
> > > Changes from v1: Convert ePMP over to Smepmp.
>
> >
>
> > Did this part get lost?
>
> >
>
> > Alistair
>
> >
>
>
> Sorry, do you mean that the term "ePMP" should be changed to "Smepmp" in 
> source code?

We still call it epmp to users and it's still marked as experimental.

See this line in the QEMU source:

MULTI_EXT_CFG_BOOL("x-epmp", epmp, false),

Alistair