[SeaBIOS] [PATCH RFC 1/2] paravirt: disable MPTable in case of more than 255 CPUs
Kevin O'Connor
kevin at koconnor.net
Mon May 9 17:12:25 CEST 2016
On Mon, May 09, 2016 at 11:43:53AM +0200, Igor Mammedov wrote:
> MPTable doesn't support more than 254 CPUs and
> QEMU supplies an alternative MADT table which
> guest will use instead of it. So do not install
> MPTable if more than 254 CPUs are provided.
>
> Signed-off-by: Igor Mammedov <imammedo at redhat.com>
> ---
> src/fw/mptable.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/src/fw/mptable.c b/src/fw/mptable.c
> index 47385cc..aec26f8 100644
> --- a/src/fw/mptable.c
> +++ b/src/fw/mptable.c
> @@ -24,6 +24,10 @@ mptable_setup(void)
> if (! CONFIG_MPTABLE)
> return;
>
> + if (romfile_loadint("etc/max-cpus", 0) > 255) {
> + dprintf(1, "MPTable doesn't support more than 254 CPUs. Skip it.\n");
> + return;
> + }
> dprintf(3, "init MPTable\n");
>
> // Config structure in temp area.
Thanks. I'd prefer to not make further modifications to fw/mptable.c
though. I think it would be better to do something like (totally
untested):
--- a/src/fw/paravirt.c
+++ b/src/fw/paravirt.c
@@ -154,8 +154,14 @@ qemu_platform_setup(void)
smp_setup();
// Create bios tables
- pirtable_setup();
- mptable_setup();
+ if (romfile_find("etc/legacy-tables-loader")) {
+ // QEMU may specify the PIR and mptable (or leave empty for no tables)
+ romfile_loader_execute("etc/legacy-tables-loader");
+ } else {
+ // Load the legacy internal tables
+ pirtable_setup();
+ mptable_setup();
+ }
smbios_setup();
if (CONFIG_FW_ROMFILE_LOAD) {
And then QEMU can create an empty fw_cfg file to suppress both the
mptable and the pir table. (Or, it can populate it to specify exactly
what QEMU wants in those tables.)
-Kevin
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