| Message ID | 20250218095130.2666580-3-luca.fancellu@arm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Prerequisite patches for Arm64 MPU build | expand |
On 18/02/2025 10:51, Luca Fancellu wrote: > > > LLC coloring can be used only on MMU system, move the code > that selects it from ARM_64 to MMU and add the ARM_64 > dependency. > > Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> Reviewed-by: Michal Orzel <michal.orzel@amd.com> ~Michal
On 18.02.2025 10:51, Luca Fancellu wrote:
> LLC coloring can be used only on MMU system,
Just for my own education: Why is this?
Jan
On 18/02/2025 14:44, Jan Beulich wrote: > > > On 18.02.2025 10:51, Luca Fancellu wrote: >> LLC coloring can be used only on MMU system, > > Just for my own education: Why is this? I read this as it refers to the feature we have in Xen, not the generic concept. You could in theory achieve cache coloring without MMU using static allocation or some custom allocator but in general we benefit from being able to map VA to PA aligning with cache coloring scheme. P.S. Personally, I've never seen a solution without MMU. ~Michal
On 18.02.2025 16:01, Orzel, Michal wrote: > On 18/02/2025 14:44, Jan Beulich wrote: >> On 18.02.2025 10:51, Luca Fancellu wrote: >>> LLC coloring can be used only on MMU system, >> >> Just for my own education: Why is this? > I read this as it refers to the feature we have in Xen, not the generic concept. > You could in theory achieve cache coloring without MMU using static allocation > or some custom allocator but in general we benefit from being able to map VA > to PA aligning with cache coloring scheme. Oh, okay. Then maybe the sentence would better be worded to express that it's our present choice, rather than an inherent limitation? Jan
diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig index a26d3e11827c..ffdff1f0a36c 100644 --- a/xen/arch/arm/Kconfig +++ b/xen/arch/arm/Kconfig @@ -8,7 +8,6 @@ config ARM_64 depends on !ARM_32 select 64BIT select HAS_FAST_MULTIPLY - select HAS_LLC_COLORING if !NUMA config ARM def_bool y @@ -76,6 +75,7 @@ choice config MMU bool "MMU" + select HAS_LLC_COLORING if !NUMA && ARM_64 select HAS_PMAP select HAS_VMAP select HAS_PASSTHROUGH
LLC coloring can be used only on MMU system, move the code that selects it from ARM_64 to MMU and add the ARM_64 dependency. Signed-off-by: Luca Fancellu <luca.fancellu@arm.com> --- v3 changes: - Dropped comment on top of boot_fdt_info() v2 changes: - dropped part of the v1 code, now this one is simpler, I will discuss better how to design a common boot flow for MPU and implement on another patch. --- --- xen/arch/arm/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)