From: Paolo Bonzini <pbonzini@redhat.com>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH v8 3/5] NX 3
Date: Fri, 1 Nov 2019 08:07:27 +0100 [thread overview]
Message-ID: <91ff125b-068d-9f4a-fa3c-ca0bfec38c17@redhat.com> (raw)
In-Reply-To: <20191101002350.GA26083@guptapadev.amr>
[-- Attachment #1: Type: text/plain, Size: 3565 bytes --]
On 01/11/19 01:24, speck for Pawan Gupta wrote:
> On Fri, Nov 01, 2019 at 12:33:45AM +0100, speck for Paolo Bonzini wrote:
>> From: Paolo Bonzini <pbonzini@redhat.com>
>> Subject: [PATCH v8 3/5] kvm: mmu: ITLB_MULTIHIT mitigation
>>
>> + kvm.nx_huge_pages=
>> + [KVM] Controls the sw workaround for bug
>> + X86_BUG_ITLB_MULTIHIT.
>> + force : Always deploy workaround.
>> + off : Default. Never deploy workaround.
>
> off is not the default in the code, so the default should be "auto" here.
>
>> + auto : Deploy workaround based on presence of
>> + X86_BUG_ITLB_MULTIHIT.
>
> Also mitigations=off is not disabling this mitigation. Below patch does
> that when mitigations=off and kvm.nx_huge_pages=auto.
>
> ---
> 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>
Thanks, I'll post v9 soon. Are you going to post backports as bundles
on top of Thomas's?
Paolo
> ---
> 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 c667844c1c42..422da241a4cb 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2653,6 +2653,12 @@
> ssbd=force-off [ARM64]
> l1tf=off [X86]
> mds=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
>
next prev parent reply other threads:[~2019-11-01 7:07 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 [this message]
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 ` [MODERATED] Re: [PATCH v2] NX mitigations=off fix Pawan Gupta
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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