Commit-ID:  70479c012b67b89e219c40eddc5dc338b7c447a3
Gitweb:     https://git.kernel.org/tip/70479c012b67b89e219c40eddc5dc338b7c447a3
Author:     Reinette Chatre <reinette.cha...@intel.com>
AuthorDate: Sat, 15 Sep 2018 14:58:23 -0700
Committer:  Thomas Gleixner <t...@linutronix.de>
CommitDate: Tue, 18 Sep 2018 23:38:06 +0200

x86/intel_rdt: Fix unchecked MSR access

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>
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
Cc: "H Peter Anvin" <h...@zytor.com>
Cc: "Tony Luck" <tony.l...@intel.com>
Cc: "Xiaochen Shen" <xiaochen.s...@intel.com>
Cc: "Chen Yu" <yu.c.c...@intel.com>
Link: 
https://lkml.kernel.org/r/1537048707-76280-6-git-send-email-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");

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