Re: [PATCH 1/1] hw/arm/sbsa-ref: bump default memory size to 2GB

[Philippe Mathieu-Daudé]

On 4/12/24 13:17, Leif Lindholm wrote:
> On 2024-12-02 10:53, Marcin Juszkiewicz wrote:
> > W dniu 26.11.2024 o 14:14, Peter Maydell pisze:
> > > On Tue, 26 Nov 2024 at 08:49, Marcin Juszkiewicz
> > > <marcin.juszkiewicz@linaro.org> wrote:
> > > > We are working on adding RME support to SBSA Reference Platform.
> > > > When RME is enabled then RMM (Realm Managment Monitor) takes 1072MB of
> > > > memory for own use. Which ends with firmware panic on 1GB machine.
> > >
> > > Reasonable change, but isn't it also a bug in the RMM that it
> > > grabs 1GB of RAM regardless of how much RAM the machine
> > > actually has?
> >
> > I think that the goal is "get it working" first and then optimize.
>
> I agree on a different platform this could feel quite hacky, but in 
> reality even 2GB falls within "ridiculously low for an SBSA platform".
>
> If we're worried about overhead for CI jobs that do not require the 
> feature, we could always conditionalize it on RME being enabled. But I'd 
> be happy to wait and see.

I'd rather do that, since it is as simple as:

-- >8 --
diff --git a/hw/arm/sbsa-ref.c b/hw/arm/sbsa-ref.c
index e3195d54497..66751d0806c 100644
--- a/hw/arm/sbsa-ref.c
+++ b/hw/arm/sbsa-ref.c
@@ -51,6 +51,7 @@
 #include "qapi/qmp/qlist.h"
 #include "qom/object.h"
 #include "target/arm/cpu-qom.h"
+#include "target/arm/cpu-features.h"
 #include "target/arm/gtimer.h"

 #define RAMLIMIT_GB 8192
@@ -795,6 +796,12 @@ static void sbsa_ref_init(MachineState *machine)
         object_unref(cpuobj);
     }

+    if (cpu_isar_feature(aa64_rme, ARM_CPU(qemu_get_cpu(0)))
+            && machine->ram_size < 2 * GiB) {
+        error_report("sbsa-ref: RME feature requires at least 2GB of RAM");
+        exit(1);
+    }
+
     memory_region_add_subregion(sysmem, sbsa_ref_memmap[SBSA_MEM].base,
                                 machine->ram);
---

$ ./qemu-system-aarch64 -M sbsa-ref -m 1G -cpu max,x-rme=on
qemu-system-aarch64: sbsa-ref: RME feature requires at least 2GB of RAM

$ ./qemu-system-aarch64 -M sbsa-ref -m 2G -cpu max,x-rme=on
// OK