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Re: [Qemu-devel] [SeaBIOS] [PATCH v2 4/5] acpi: load and link tables fro
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [SeaBIOS] [PATCH v2 4/5] acpi: load and link tables from /etc/acpi/ |
Date: |
Mon, 15 Jul 2013 12:58:51 +0300 |
On Mon, Jul 15, 2013 at 11:11:59AM +0300, Michael S. Tsirkin wrote:
> On Sun, Jul 14, 2013 at 02:27:14PM -0400, Kevin O'Connor wrote:
> > On Sun, Jul 07, 2013 at 06:42:43PM +0300, Michael S. Tsirkin wrote:
> > > Load files in /etc/acpi/, link them using
> > > a linker script and use for acpi tables, including the RSDP.
> > > Presense of RSDP in this directory completely disables
> > > generating and loading legacy acpi tables.
> > >
> > > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > > ---
> > > src/acpi.c | 39 +++++++++++++++++++++++++++++++++++++++
> > > 1 file changed, 39 insertions(+)
> > >
> > > diff --git a/src/acpi.c b/src/acpi.c
> > > index a81f0cb..07d311a 100644
> > > --- a/src/acpi.c
> > > +++ b/src/acpi.c
> > > @@ -27,6 +27,7 @@
> > > #include "config.h" // CONFIG_*
> > > #include "paravirt.h" // RamSize
> > > #include "dev-q35.h"
> > > +#include "linker.h"
> > >
> > > #include "acpi-dsdt.hex"
> > >
> > > @@ -599,6 +600,34 @@ static const struct pci_device_id acpi_find_tbl[] = {
> > >
> > > struct rsdp_descriptor *RsdpAddr;
> > >
> > > +/* Look for RSDP signature in files loaded in FSEG */
> > > +struct rsdp_descriptor *
> > > +acpi_find_rsdp_rom(void)
> > > +{
> > > + struct romfile_s *file = NULL;
> > > + struct rsdp_descriptor *rsdp = NULL;
> > > + for (;;) {
> > > + file = romfile_findprefix("", file);
> > > + if (!file)
> > > + break;
> > > +
> > > + if (!file->data || !pmm_test_fseg(file->data) ||
> > > + file->size < sizeof(rsdp->signature))
> > > + continue;
> > > +
> > > + void *data;
> > > +
> > > + for (data = file->data;
> > > + data + sizeof(*rsdp) <= file->data + file->size;
> > > + data++) {
> > > + rsdp = data;
> > > + if (rsdp->signature == cpu_to_le64(RSDP_SIGNATURE))
> > > + return rsdp;
> > > + }
> > > + }
> > > + return NULL;
> > > +}
> > > +
> > > #define MAX_ACPI_TABLES 20
> > > void
> > > acpi_setup(void)
> > > @@ -608,6 +637,16 @@ acpi_setup(void)
> > >
> > > dprintf(3, "init ACPI tables\n");
> > >
> > > + linker_loader_execute("/etc/linker-script");
> > > +
> > > + RsdpAddr = acpi_find_rsdp_rom();
> > > +
> > > + if (RsdpAddr) {
> > > + return;
> > > + }
> >
> > I don't understand this. Why not use the presence of
> > "/etc/linker-script" to determine if ACPI should be produced.
>
> We can do this but what do we do if linker script is there
> but no rsdp?
> Maybe just add
> test -e /etc/linker-script != RsdpAddr
> dprintf(1, "linker script found but no rsdp. Falling back on
> builtin tables\n");
>
> Would this address your comment?
>
And just to clarify, in my eyes it's preferable to use
acpi_find_rsdp_rom which is based on ACPI standard than
look for a specific PV interface.
For example, one can imagine a hypervisor that maps
ACPI tables directly into guest memory. Looking for
rsdp in fseg memory will work, relying on the
linker won't.
> > Also, /etc/linker-script is not very informative - how about something
> > like "/etc/biostables".
> >
> > -Kevin
>
> Hmm bios seems redundant, and tables makes one think it's the tables
> themselves.
>
> "/etc/acpi-linker"
> "/etc/acpi-loader"?
>
>
> --
> MST