diff options
Diffstat (limited to 'common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-amd-don-t-set-X86_BUG_SYSRET_SS_ATTRS-when-runni.patch')
| -rw-r--r-- | common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-amd-don-t-set-X86_BUG_SYSRET_SS_ATTRS-when-runni.patch | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-amd-don-t-set-X86_BUG_SYSRET_SS_ATTRS-when-runni.patch b/common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-amd-don-t-set-X86_BUG_SYSRET_SS_ATTRS-when-runni.patch new file mode 100644 index 00000000..39d81c71 --- /dev/null +++ b/common/recipes-kernel/linux/linux-yocto-4.9.21/0021-x86-amd-don-t-set-X86_BUG_SYSRET_SS_ATTRS-when-runni.patch @@ -0,0 +1,66 @@ +From 5fb8da20577a159d311db9c29e62dbb782529571 Mon Sep 17 00:00:00 2001 +From: David Woodhouse <dwmw@amazon.co.uk> +Date: Sun, 20 May 2018 20:51:10 +0100 +Subject: [PATCH 21/93] x86/amd: don't set X86_BUG_SYSRET_SS_ATTRS when running + under Xen + +commit def9331a12977770cc6132d79f8e6565871e8e38 upstream + +When running as Xen pv guest X86_BUG_SYSRET_SS_ATTRS must not be set +on AMD cpus. + +This bug/feature bit is kind of special as it will be used very early +when switching threads. Setting the bit and clearing it a little bit +later leaves a critical window where things can go wrong. This time +window has enlarged a little bit by using setup_clear_cpu_cap() instead +of the hypervisor's set_cpu_features callback. It seems this larger +window now makes it rather easy to hit the problem. + +The proper solution is to never set the bit in case of Xen. + +Signed-off-by: Juergen Gross <jgross@suse.com> +Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com> +Acked-by: Thomas Gleixner <tglx@linutronix.de> +Signed-off-by: Juergen Gross <jgross@suse.com> +Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> +Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> +--- + arch/x86/kernel/cpu/amd.c | 5 +++-- + arch/x86/xen/enlighten.c | 4 +--- + 2 files changed, 4 insertions(+), 5 deletions(-) + +diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c +index c375bc6..747f8a2 100644 +--- a/arch/x86/kernel/cpu/amd.c ++++ b/arch/x86/kernel/cpu/amd.c +@@ -824,8 +824,9 @@ static void init_amd(struct cpuinfo_x86 *c) + if (cpu_has(c, X86_FEATURE_3DNOW) || cpu_has(c, X86_FEATURE_LM)) + set_cpu_cap(c, X86_FEATURE_3DNOWPREFETCH); + +- /* AMD CPUs don't reset SS attributes on SYSRET */ +- set_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS); ++ /* AMD CPUs don't reset SS attributes on SYSRET, Xen does. */ ++ if (!cpu_has(c, X86_FEATURE_XENPV)) ++ set_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS); + } + + #ifdef CONFIG_X86_32 +diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c +index 5226379..8b97c87 100644 +--- a/arch/x86/xen/enlighten.c ++++ b/arch/x86/xen/enlighten.c +@@ -1968,10 +1968,8 @@ EXPORT_SYMBOL_GPL(xen_hvm_need_lapic); + + static void xen_set_cpu_features(struct cpuinfo_x86 *c) + { +- if (xen_pv_domain()) { +- clear_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS); ++ if (xen_pv_domain()) + set_cpu_cap(c, X86_FEATURE_XENPV); +- } + } + + static void xen_pin_vcpu(int cpu) +-- +2.7.4 + |