linux-kernel - Re: [PATCH v13 03/18] arm64: hyp-stub: Move el1

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Date:   Thu, 8 Apr 2021 10:45:18 -0400
From:   Pavel Tatashin <pasha.tatashin@...een.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     James Morris <jmorris@...ei.org>, Sasha Levin <sashal@...nel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        kexec mailing list <kexec@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        James Morse <james.morse@....com>,
        Vladimir Murzin <vladimir.murzin@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-mm <linux-mm@...ck.org>,
        Mark Rutland <mark.rutland@....com>, steve.capper@....com,
        rfontana@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
        Selin Dag <selindag@...il.com>,
        Tyler Hicks <tyhicks@...ux.microsoft.com>,
        Pingfan Liu <kernelfans@...il.com>
Subject: Re: [PATCH v13 03/18] arm64: hyp-stub: Move el1_sync into the vectors

On Thu, Apr 8, 2021 at 6:24 AM Marc Zyngier <maz@...nel.org> wrote:
>
> On 2021-04-08 05:05, Pavel Tatashin wrote:
> > From: James Morse <james.morse@....com>
> >
> > The hyp-stub's el1_sync code doesn't do very much, this can easily fit
> > in the vectors.
> >
> > With this, all of the hyp-stubs behaviour is contained in its vectors.
> > This lets kexec and hibernate copy the hyp-stub when they need its
> > behaviour, instead of re-implementing it.
> >
> > Signed-off-by: James Morse <james.morse@....com>
> >
> > [Fixed merging issues]
>
> That's a pretty odd fix IMO.
>
> >
> > Signed-off-by: Pavel Tatashin <pasha.tatashin@...een.com>
> > ---
> >  arch/arm64/kernel/hyp-stub.S | 59 ++++++++++++++++++------------------
> >  1 file changed, 29 insertions(+), 30 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/hyp-stub.S
> > b/arch/arm64/kernel/hyp-stub.S
> > index ff329c5c074d..d1a73d0f74e0 100644
> > --- a/arch/arm64/kernel/hyp-stub.S
> > +++ b/arch/arm64/kernel/hyp-stub.S
> > @@ -21,6 +21,34 @@ SYM_CODE_START_LOCAL(\label)
> >       .align 7
> >       b       \label
> >  SYM_CODE_END(\label)
> > +.endm
> > +
> > +.macro hyp_stub_el1_sync
> > +SYM_CODE_START_LOCAL(hyp_stub_el1_sync)
> > +     .align 7
> > +     cmp     x0, #HVC_SET_VECTORS
> > +     b.ne    2f
> > +     msr     vbar_el2, x1
> > +     b       9f
> > +
> > +2:   cmp     x0, #HVC_SOFT_RESTART
> > +     b.ne    3f
> > +     mov     x0, x2
> > +     mov     x2, x4
> > +     mov     x4, x1
> > +     mov     x1, x3
> > +     br      x4                              // no return
> > +
> > +3:   cmp     x0, #HVC_RESET_VECTORS
> > +     beq     9f                              // Nothing to reset!
> > +
> > +     /* Someone called kvm_call_hyp() against the hyp-stub... */
> > +     mov_q   x0, HVC_STUB_ERR
> > +     eret
> > +
> > +9:   mov     x0, xzr
> > +     eret
> > +SYM_CODE_END(hyp_stub_el1_sync)
>
> You said you tested this on a TX2. I guess you don't care whether
> it runs VHE or not...

Hi Marc,

Thank you for noticing this. Not sure how this missmerge happened. I
have added the missing case, and VHE is initialized correctly during
boot.
[   14.698175] kvm [1]: VHE mode initialized successfully

During normal boot, kexec reboot, and kdump reboot. I will respin the
series and send the version 14 soon.

Thanks,
Pasha

>
>          M.
>
> >  .endm
> >
> >       .text
> > @@ -39,7 +67,7 @@ SYM_CODE_START(__hyp_stub_vectors)
> >       invalid_vector  hyp_stub_el2h_fiq_invalid       // FIQ EL2h
> >       invalid_vector  hyp_stub_el2h_error_invalid     // Error EL2h
> >
> > -     ventry  el1_sync                        // Synchronous 64-bit EL1
> > +     hyp_stub_el1_sync                               // Synchronous 64-bit EL1
> >       invalid_vector  hyp_stub_el1_irq_invalid        // IRQ 64-bit EL1
> >       invalid_vector  hyp_stub_el1_fiq_invalid        // FIQ 64-bit EL1
> >       invalid_vector  hyp_stub_el1_error_invalid      // Error 64-bit EL1
> > @@ -55,35 +83,6 @@ SYM_CODE_END(__hyp_stub_vectors)
> >  # Check the __hyp_stub_vectors didn't overflow
> >  .org . - (__hyp_stub_vectors_end - __hyp_stub_vectors) + SZ_2K
> >
> > -
> > -SYM_CODE_START_LOCAL(el1_sync)
> > -     cmp     x0, #HVC_SET_VECTORS
> > -     b.ne    1f
> > -     msr     vbar_el2, x1
> > -     b       9f
> > -
> > -1:   cmp     x0, #HVC_VHE_RESTART
> > -     b.eq    mutate_to_vhe
> > -
> > -2:   cmp     x0, #HVC_SOFT_RESTART
> > -     b.ne    3f
> > -     mov     x0, x2
> > -     mov     x2, x4
> > -     mov     x4, x1
> > -     mov     x1, x3
> > -     br      x4                              // no return
> > -
> > -3:   cmp     x0, #HVC_RESET_VECTORS
> > -     beq     9f                              // Nothing to reset!
> > -
> > -     /* Someone called kvm_call_hyp() against the hyp-stub... */
> > -     mov_q   x0, HVC_STUB_ERR
> > -     eret
> > -
> > -9:   mov     x0, xzr
> > -     eret
> > -SYM_CODE_END(el1_sync)
> > -
> >  // nVHE? No way! Give me the real thing!
> >  SYM_CODE_START_LOCAL(mutate_to_vhe)
> >       // Sanity check: MMU *must* be off
>
> --
> Jazz is not dead. It just smells funny...