[PATCH V2 5/9] x86/intel_rdt: Fix unchecked MSR access

[Fenghua Yu]

From: Reinette Chatre <reinette.cha...@intel.com>

When a new resource group is created, it is initialized with sane
defaults that currently assume the resource being initialized is a CAT
resource. This code path is also followed by a MBA resource that is not
allocated the same as a CAT resource and as a result we encounter the
following unchecked MSR access error:

unchecked MSR access error: WRMSR to 0xd51 (tried to write 0x0000
000000000064) at rIP: 0xffffffffae059994 (native_write_msr+0x4/0x20)
Call Trace:
mba_wrmsr+0x41/0x80
update_domains+0x125/0x130
rdtgroup_mkdir+0x270/0x500

Fix the above by ensuring the initial allocation is only attempted on a
CAT resource.

Fixes: 95f0b77ef ("x86/intel_rdt: Initialize new resource group with sane 
defaults")
Signed-off-by: Reinette Chatre <reinette.cha...@intel.com>
Signed-off-by: Fenghua Yu <fenghua...@intel.com>
---
 arch/x86/kernel/cpu/intel_rdt_rdtgroup.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c 
b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
index ea91750ba27f..74821bc457c0 100644
--- a/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
+++ b/arch/x86/kernel/cpu/intel_rdt_rdtgroup.c
@@ -2349,6 +2349,12 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
        u32 *ctrl;
 
        for_each_alloc_enabled_rdt_resource(r) {
+               /*
+                * Only initialize default allocations for CBM cache
+                * resources
+                */
+               if (r->rid == RDT_RESOURCE_MBA)
+                       continue;
                list_for_each_entry(d, &r->domains, list) {
                        d->have_new_ctrl = false;
                        d->new_ctrl = r->cache.shareable_bits;
@@ -2386,6 +2392,12 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
        }
 
        for_each_alloc_enabled_rdt_resource(r) {
+               /*
+                * Only initialize default allocations for CBM cache
+                * resources
+                */
+               if (r->rid == RDT_RESOURCE_MBA)
+                       continue;
                ret = update_domains(r, rdtgrp->closid);
                if (ret < 0) {
                        rdt_last_cmd_puts("failed to initialize allocations\n");
-- 
2.19.0