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authorLuis R. Rodriguez <mcgrof@suse.com>2015-05-26 10:28:14 +0200
committerIngo Molnar <mingo@kernel.org>2015-05-27 14:41:01 +0200
commitf9626104a5b6815ec7d65789dfb900af5fa51e64 (patch)
treeafaf68aeaf593478bf2df8ef048b85819ee0b680 /arch/x86/kernel/cpu/mtrr/main.c
parent7d010fdf299929f9583ce5e17da629dcd83c36ef (diff)
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x86/mm/mtrr: Generalize runtime disabling of MTRRs
It is possible to enable CONFIG_MTRR and CONFIG_X86_PAT and end up with a system with MTRR functionality disabled but PAT functionality enabled. This can happen, for instance, when the Xen hypervisor is used where MTRRs are not supported but PAT is. This can happen on Linux as of commit 47591df50512 ("xen: Support Xen pv-domains using PAT") by Juergen, introduced in v3.19. Technically, we should assume the proper CPU bits would be set to disable MTRRs but we can't always rely on this. At least on the Xen Hypervisor, for instance, only X86_FEATURE_MTRR was disabled as of Xen 4.4 through Xen commit 586ab6a [0], but not X86_FEATURE_K6_MTRR, X86_FEATURE_CENTAUR_MCR, or X86_FEATURE_CYRIX_ARR for instance. Roger Pau Monné has clarified though that although this is technically true we will never support PVH on these CPU types so Xen has no need to disable these bits on those systems. As per Roger, AMD K6, Centaur and VIA chips don't have the necessary hardware extensions to allow running PVH guests [1]. As per Toshi it is also possible for the BIOS to disable MTRR support, in such cases get_mtrr_state() would update the MTRR state as per the BIOS, we need to propagate this information as well. x86 MTRR code relies on quite a bit of checks for mtrr_if being set to check to see if MTRRs did get set up. Instead, lets provide a generic getter for that. This also adds a few checks where they were not before which could potentially safeguard ourselves against incorrect usage of MTRR where this was not desirable. Where possible match error codes as if MTRRs were disabled on arch/x86/include/asm/mtrr.h. Lastly, since disabling MTRRs can happen at run time and we could end up with PAT enabled, best record now in our logs when MTRRs are disabled. [0] ~/devel/xen (git::stable-4.5)$ git describe --contains 586ab6a 4.4.0-rc1~18 [1] http://lists.xenproject.org/archives/html/xen-devel/2015-03/msg03460.html Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Antonino Daplas <adaplas@gmail.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Cc: Dave Airlie <airlied@redhat.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Davidlohr Bueso <dbueso@suse.de> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com> Cc: Juergen Gross <jgross@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Roger Pau Monné <roger.pau@citrix.com> Cc: Stefan Bader <stefan.bader@canonical.com> Cc: Suresh Siddha <sbsiddha@gmail.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com> Cc: Toshi Kani <toshi.kani@hp.com> Cc: Ville Syrjälä <syrjala@sci.fi> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: bhelgaas@google.com Cc: david.vrabel@citrix.com Cc: jbeulich@suse.com Cc: konrad.wilk@oracle.com Cc: venkatesh.pallipadi@intel.com Cc: ville.syrjala@linux.intel.com Cc: xen-devel@lists.xensource.com Link: http://lkml.kernel.org/r/1426893517-2511-3-git-send-email-mcgrof@do-not-panic.com Link: http://lkml.kernel.org/r/1432628901-18044-12-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/cpu/mtrr/main.c')
-rw-r--r--arch/x86/kernel/cpu/mtrr/main.c39
1 files changed, 31 insertions, 8 deletions
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 81baf5f..383efb2 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -59,6 +59,12 @@
#define MTRR_TO_PHYS_WC_OFFSET 1000
u32 num_var_ranges;
+static bool __mtrr_enabled;
+
+static bool mtrr_enabled(void)
+{
+ return __mtrr_enabled;
+}
unsigned int mtrr_usage_table[MTRR_MAX_VAR_RANGES];
static DEFINE_MUTEX(mtrr_mutex);
@@ -286,7 +292,7 @@ int mtrr_add_page(unsigned long base, unsigned long size,
int i, replace, error;
mtrr_type ltype;
- if (!mtrr_if)
+ if (!mtrr_enabled())
return -ENXIO;
error = mtrr_if->validate_add_page(base, size, type);
@@ -435,6 +441,8 @@ static int mtrr_check(unsigned long base, unsigned long size)
int mtrr_add(unsigned long base, unsigned long size, unsigned int type,
bool increment)
{
+ if (!mtrr_enabled())
+ return -ENODEV;
if (mtrr_check(base, size))
return -EINVAL;
return mtrr_add_page(base >> PAGE_SHIFT, size >> PAGE_SHIFT, type,
@@ -463,8 +471,8 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size)
unsigned long lbase, lsize;
int error = -EINVAL;
- if (!mtrr_if)
- return -ENXIO;
+ if (!mtrr_enabled())
+ return -ENODEV;
max = num_var_ranges;
/* No CPU hotplug when we change MTRR entries */
@@ -523,6 +531,8 @@ int mtrr_del_page(int reg, unsigned long base, unsigned long size)
*/
int mtrr_del(int reg, unsigned long base, unsigned long size)
{
+ if (!mtrr_enabled())
+ return -ENODEV;
if (mtrr_check(base, size))
return -EINVAL;
return mtrr_del_page(reg, base >> PAGE_SHIFT, size >> PAGE_SHIFT);
@@ -548,7 +558,7 @@ int arch_phys_wc_add(unsigned long base, unsigned long size)
{
int ret;
- if (pat_enabled)
+ if (pat_enabled || !mtrr_enabled())
return 0; /* Success! (We don't need to do anything.) */
ret = mtrr_add(base, size, MTRR_TYPE_WRCOMB, true);
@@ -737,10 +747,12 @@ void __init mtrr_bp_init(void)
}
if (mtrr_if) {
+ __mtrr_enabled = true;
set_num_var_ranges();
init_table();
if (use_intel()) {
- get_mtrr_state();
+ /* BIOS may override */
+ __mtrr_enabled = get_mtrr_state();
if (mtrr_cleanup(phys_addr)) {
changed_by_mtrr_cleanup = 1;
@@ -748,10 +760,16 @@ void __init mtrr_bp_init(void)
}
}
}
+
+ if (!mtrr_enabled())
+ pr_info("MTRR: Disabled\n");
}
void mtrr_ap_init(void)
{
+ if (!mtrr_enabled())
+ return;
+
if (!use_intel() || mtrr_aps_delayed_init)
return;
/*
@@ -777,6 +795,9 @@ void mtrr_save_state(void)
{
int first_cpu;
+ if (!mtrr_enabled())
+ return;
+
get_online_cpus();
first_cpu = cpumask_first(cpu_online_mask);
smp_call_function_single(first_cpu, mtrr_save_fixed_ranges, NULL, 1);
@@ -785,6 +806,8 @@ void mtrr_save_state(void)
void set_mtrr_aps_delayed_init(void)
{
+ if (!mtrr_enabled())
+ return;
if (!use_intel())
return;
@@ -796,7 +819,7 @@ void set_mtrr_aps_delayed_init(void)
*/
void mtrr_aps_init(void)
{
- if (!use_intel())
+ if (!use_intel() || !mtrr_enabled())
return;
/*
@@ -813,7 +836,7 @@ void mtrr_aps_init(void)
void mtrr_bp_restore(void)
{
- if (!use_intel())
+ if (!use_intel() || !mtrr_enabled())
return;
mtrr_if->set_all();
@@ -821,7 +844,7 @@ void mtrr_bp_restore(void)
static int __init mtrr_init_finialize(void)
{
- if (!mtrr_if)
+ if (!mtrr_enabled())
return 0;
if (use_intel()) {
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