From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH v2] NX mitigations=off fix
Date: Fri, 1 Nov 2019 14:38:31 -0700 [thread overview]
Message-ID: <20191101213831.GB26083@guptapadev.amr> (raw)
In-Reply-To: <20191101203859.GA10998@sec>
From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Date: Wed, 30 Oct 2019 21:28:24 -0700
Subject: [PATCH] kvm: x86: mmu: Apply global mitigations knob to ITLB_MULTIHIT
Problem: The global mitigation knob mitigations=off does not turn off
X86_BUG_ITLB_MULTIHIT mitigation.
Fix: Turn off the mitigation when ITLB_MULTIHIT mitigation mode is
"auto" and mitigations are turned off globally via cmdline
mitigations=off.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
Rebased on taa-master bundle. I do not have access to Thomas's repo.
This needs to go on top of Tyler's fix.
Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
arch/x86/kvm/mmu.c | 10 ++++++++--
2 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e8e0a140a632..555236b92289 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2654,6 +2654,12 @@
l1tf=off [X86]
mds=off [X86]
tsx_async_abort=off [X86]
+ kvm.nx_huge_pages=off [X86]
+
+ Exceptions:
+ This does not have any effect on
+ kvm.nx_huge_pages when
+ kvm.nx_huge_pages=force.
auto (default)
Mitigate all CPU vulnerabilities, but leave SMT
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index e6a5748a12d5..529589a42afb 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -6250,6 +6250,12 @@ static void kvm_set_mmio_spte_mask(void)
kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);
}
+static bool get_nx_auto_mode(void)
+{
+ /* Return true when CPU has the bug, and mitigations are ON */
+ return boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT) && !cpu_mitigations_off();
+}
+
static void __set_nx_huge_pages(bool val)
{
nx_huge_pages = itlb_multihit_kvm_mitigation = val;
@@ -6266,7 +6272,7 @@ static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
else if (sysfs_streq(val, "force"))
new_val = 1;
else if (sysfs_streq(val, "auto"))
- new_val = boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT);
+ new_val = get_nx_auto_mode();
else if (strtobool(val, &new_val) < 0)
return -EINVAL;
@@ -6296,7 +6302,7 @@ int kvm_mmu_module_init(void)
int ret = -ENOMEM;
if (nx_huge_pages == -1)
- __set_nx_huge_pages(boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT));
+ __set_nx_huge_pages(get_nx_auto_mode());
/*
* MMU roles use union aliasing which is, generally speaking, an
--
2.20.1
next prev parent reply other threads:[~2019-11-01 21:45 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-31 23:33 [MODERATED] [PATCH v8 0/5] NX 0 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 1/5] NX 1 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 2/5] NX 2 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 3/5] NX 3 Paolo Bonzini
2019-11-01 0:24 ` [MODERATED] " Pawan Gupta
2019-11-01 7:07 ` Paolo Bonzini
2019-11-01 18:38 ` mark gross
2019-11-01 18:51 ` Tyler Hicks
2019-11-01 20:36 ` mark gross
2019-11-02 7:36 ` Paolo Bonzini
2019-11-01 14:58 ` Tyler Hicks
2019-11-01 15:43 ` [MODERATED] [PATCH] NX build fixup Tyler Hicks
2019-11-01 16:31 ` [MODERATED] " Josh Poimboeuf
2019-11-01 20:39 ` [MODERATED] [PATCH v2] " Tyler Hicks
2019-11-01 21:14 ` [MODERATED] " Josh Poimboeuf
2019-11-01 21:38 ` Pawan Gupta [this message]
2019-10-31 23:33 ` [MODERATED] [PATCH v8 4/5] NX 4 Paolo Bonzini
2019-10-31 23:33 ` [MODERATED] [PATCH v8 5/5] NX 5 Paolo Bonzini
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