RE: [PATCH 1/1] accel/tcg: Allow the second page of an instruction to be MMIO

[Sid Manning]

> -----Original Message-----
> From: Jørgen Hansen <Jorgen.Hansen@wdc.com>
> Sent: Tuesday, February 7, 2023 9:03 AM
> To: Richard Henderson <richard.henderson@linaro.org>; qemu-
> devel@nongnu.org
> Cc: Sid Manning <sidneym@quicinc.com>; Mark Burton
> <mburton@qti.qualcomm.com>; Brian Cain <bcain@quicinc.com>; Matheus
> Bernardino <mathbern@qti.qualcomm.com>; Ajay Joshi
> <Ajay.Joshi@wdc.com>
> Subject: Re: [PATCH 1/1] accel/tcg: Allow the second page of an instruction to
> be MMIO
> 
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> of any links or attachments, and do not enable macros.
> 
> On 2/6/23 20:38, Richard Henderson wrote:
> > If an instruction straddles a page boundary, and the first page was
> > ram, but the second page was MMIO, we would abort.  Handle this as if
> > both pages are MMIO, by setting the ram_addr_t for the first page to
> > -1.
> >
> > Reported-by: Sid Manning <sidneym@quicinc.com>
> > Reported-by: Jørgen Hansen <Jorgen.Hansen@wdc.com>
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> >   accel/tcg/translator.c | 12 ++++++++++--
> >   1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c index
> > ef5193c67e..1cf404ced0 100644
> > --- a/accel/tcg/translator.c
> > +++ b/accel/tcg/translator.c
> > @@ -176,8 +176,16 @@ static void *translator_access(CPUArchState *env,
> DisasContextBase *db,
> >           if (host == NULL) {
> >               tb_page_addr_t phys_page =
> >                   get_page_addr_code_hostp(env, base, &db->host_addr[1]);
> > -            /* We cannot handle MMIO as second page. */
> > -            assert(phys_page != -1);
> > +
> > +            /*
> > +             * If the second page is MMIO, treat as if the first page
> > +             * was MMIO as well, so that we do not cache the TB.
> > +             */
> > +            if (unlikely(phys_page == -1)) {
> > +                tb_set_page_addr0(tb, -1);
> > +                return NULL;
> > +            }
> > +
> >               tb_set_page_addr1(tb, phys_page);
> >   #ifdef CONFIG_USER_ONLY
> >               page_protect(end);
> > --
> > 2.34.1
> >
> 
> Thanks a lot for the quick turnaround. I've verified that the patch resolves
> the issue we experienced.

I also verified this patch fixed my issue.  Thanks!