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Re: [PATCH v4 07/17] target/ppc: Disconnect hflags from MSR
From: |
David Gibson |
Subject: |
Re: [PATCH v4 07/17] target/ppc: Disconnect hflags from MSR |
Date: |
Tue, 23 Mar 2021 10:54:47 +1100 |
On Mon, Mar 22, 2021 at 10:55:46AM -0600, Richard Henderson wrote:
> On 3/21/21 9:52 PM, David Gibson wrote:
> > > +/*
> > > + * Bits for env->hflags.
> > > + *
> > > + * Most of these bits overlap with corresponding bits in MSR,
> > > + * but some come from other sources. Be cautious when modifying.
> >
> > Yeah.. I'm not sure "be cautious" is enough of a warning. The exact
> > value of some but not all of these flags must equal that for the
> > corresponding MSR bits, which is terrifyingly subtle.
>
> Fair. How about, for the comment here, "This is validated in
> hreg_compute_hflags."
>
> > > + /* Some bits come straight across from MSR. */
> > > + msr_mask = ((1 << MSR_LE) | (1 << MSR_PR) |
> > > + (1 << MSR_DR) | (1 << MSR_IR) |
> > > + (1 << MSR_FP) | (1 << MSR_SA) | (1 << MSR_AP));
>
> Here, and in every other spot within this function where we manipulate
> msr_mask,
>
> QEMU_BUILD_BUG_ON(MSR_LE != HFLAGS_LE);
Seems reasonable.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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[PATCH v4 04/17] target/ppc: Do not call hreg_compute_mem_idx after ppc_store_msr, Richard Henderson, 2021/03/15
[PATCH v4 07/17] target/ppc: Disconnect hflags from MSR, Richard Henderson, 2021/03/15
[PATCH v4 06/17] target/ppc: Fix comment for MSR_FE{0,1}, Richard Henderson, 2021/03/15
[PATCH v4 08/17] target/ppc: Reduce env->hflags to uint32_t, Richard Henderson, 2021/03/15
[PATCH v4 05/17] target/ppc: Retain hflags_nmsr only for migration, Richard Henderson, 2021/03/15