4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Andy Lutomirski <l...@kernel.org> commit 660da7c9228f685b2ebe664f9fd69aaddcc420b5 upstream. We can use PCID if the CPU has PCID and PGE and we're not on Xen. By itself, this has no effect. A followup patch will start using PCID. Signed-off-by: Andy Lutomirski <l...@kernel.org> Reviewed-by: Nadav Amit <nadav.a...@gmail.com> Reviewed-by: Boris Ostrovsky <boris.ostrov...@oracle.com> Reviewed-by: Thomas Gleixner <t...@linutronix.de> Cc: Andrew Morton <a...@linux-foundation.org> Cc: Arjan van de Ven <ar...@linux.intel.com> Cc: Borislav Petkov <b...@alien8.de> Cc: Dave Hansen <dave.han...@intel.com> Cc: Juergen Gross <jgr...@suse.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Mel Gorman <mgor...@suse.de> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Rik van Riel <r...@redhat.com> Cc: linux...@kvack.org Link: http://lkml.kernel.org/r/6327ecd907b32f79d5aa0d466f04503bbec5df88.1498751203.git.l...@kernel.org Signed-off-by: Ingo Molnar <mi...@kernel.org> Cc: Hugh Dickins <hu...@google.com> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- arch/x86/include/asm/tlbflush.h | 8 ++++++++ arch/x86/kernel/cpu/common.c | 22 ++++++++++++++++++++++ arch/x86/xen/enlighten.c | 6 ++++++ 3 files changed, 36 insertions(+) --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -191,6 +191,14 @@ static inline void __flush_tlb_all(void) __flush_tlb_global(); else __flush_tlb(); + + /* + * Note: if we somehow had PCID but not PGE, then this wouldn't work -- + * we'd end up flushing kernel translations for the current ASID but + * we might fail to flush kernel translations for other cached ASIDs. + * + * To avoid this issue, we force PCID off if PGE is off. + */ } static inline void __flush_tlb_one(unsigned long addr) --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -324,6 +324,25 @@ static __always_inline void setup_smap(s } } +static void setup_pcid(struct cpuinfo_x86 *c) +{ + if (cpu_has(c, X86_FEATURE_PCID)) { + if (cpu_has(c, X86_FEATURE_PGE)) { + cr4_set_bits(X86_CR4_PCIDE); + } else { + /* + * flush_tlb_all(), as currently implemented, won't + * work if PCID is on but PGE is not. Since that + * combination doesn't exist on real hardware, there's + * no reason to try to fully support it, but it's + * polite to avoid corrupting data if we're on + * an improperly configured VM. + */ + clear_cpu_cap(c, X86_FEATURE_PCID); + } + } +} + /* * Protection Keys are not available in 32-bit mode. */ @@ -1082,6 +1101,9 @@ static void identify_cpu(struct cpuinfo_ setup_smep(c); setup_smap(c); + /* Set up PCID */ + setup_pcid(c); + /* * The vendor-specific functions might have changed features. * Now we do "generic changes." --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -444,6 +444,12 @@ static void __init xen_init_cpuid_mask(v ~((1 << X86_FEATURE_MTRR) | /* disable MTRR */ (1 << X86_FEATURE_ACC)); /* thermal monitoring */ + /* + * Xen PV would need some work to support PCID: CR3 handling as well + * as xen_flush_tlb_others() would need updating. + */ + cpuid_leaf1_ecx_mask &= ~(1 << (X86_FEATURE_PCID % 32)); /* disable PCID */ + if (!xen_initial_domain()) cpuid_leaf1_edx_mask &= ~((1 << X86_FEATURE_ACPI)); /* disable ACPI */
