4.9-stable review patch. If anyone has any objections, please let me know.
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From: James Morse james.morse@arm.com
Commit 6d99b68933fbcf51f84fcbba49246ce1209ec193 upstream.
Now that KVM uses tpidr_el2 in the same way as Linux's cpu_offset in tpidr_el1, merge the two. This saves KVM from save/restoring tpidr_el1 on VHE hosts, and allows future code to blindly access per-cpu variables without triggering world-switch.
Signed-off-by: James Morse james.morse@arm.com Reviewed-by: Christoffer Dall cdall@linaro.org Reviewed-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Marc Zyngier marc.zyngier@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/alternative.h | 2 ++ arch/arm64/include/asm/assembler.h | 8 ++++++++ arch/arm64/include/asm/percpu.h | 12 ++++++++++-- arch/arm64/kernel/alternative.c | 9 +++++---- arch/arm64/kernel/cpufeature.c | 17 +++++++++++++++++ 5 files changed, 42 insertions(+), 6 deletions(-)
--- a/arch/arm64/include/asm/alternative.h +++ b/arch/arm64/include/asm/alternative.h @@ -11,6 +11,8 @@ #include <linux/stddef.h> #include <linux/stringify.h>
+extern int alternatives_applied; + struct alt_instr { s32 orig_offset; /* offset to original instruction */ s32 alt_offset; /* offset to replacement instruction */ --- a/arch/arm64/include/asm/assembler.h +++ b/arch/arm64/include/asm/assembler.h @@ -245,7 +245,11 @@ lr .req x30 // link register */ .macro adr_this_cpu, dst, sym, tmp adr_l \dst, \sym +alternative_if_not ARM64_HAS_VIRT_HOST_EXTN mrs \tmp, tpidr_el1 +alternative_else + mrs \tmp, tpidr_el2 +alternative_endif add \dst, \dst, \tmp .endm
@@ -256,7 +260,11 @@ lr .req x30 // link register */ .macro ldr_this_cpu dst, sym, tmp adr_l \dst, \sym +alternative_if_not ARM64_HAS_VIRT_HOST_EXTN mrs \tmp, tpidr_el1 +alternative_else + mrs \tmp, tpidr_el2 +alternative_endif ldr \dst, [\dst, \tmp] .endm
--- a/arch/arm64/include/asm/percpu.h +++ b/arch/arm64/include/asm/percpu.h @@ -16,9 +16,14 @@ #ifndef __ASM_PERCPU_H #define __ASM_PERCPU_H
+#include <asm/alternative.h> + static inline void set_my_cpu_offset(unsigned long off) { - asm volatile("msr tpidr_el1, %0" :: "r" (off) : "memory"); + asm volatile(ALTERNATIVE("msr tpidr_el1, %0", + "msr tpidr_el2, %0", + ARM64_HAS_VIRT_HOST_EXTN) + :: "r" (off) : "memory"); }
static inline unsigned long __my_cpu_offset(void) @@ -29,7 +34,10 @@ static inline unsigned long __my_cpu_off * We want to allow caching the value, so avoid using volatile and * instead use a fake stack read to hazard against barrier(). */ - asm("mrs %0, tpidr_el1" : "=r" (off) : + asm(ALTERNATIVE("mrs %0, tpidr_el1", + "mrs %0, tpidr_el2", + ARM64_HAS_VIRT_HOST_EXTN) + : "=r" (off) : "Q" (*(const unsigned long *)current_stack_pointer));
return off; --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -32,6 +32,8 @@ #define ALT_ORIG_PTR(a) __ALT_PTR(a, orig_offset) #define ALT_REPL_PTR(a) __ALT_PTR(a, alt_offset)
+int alternatives_applied; + struct alt_region { struct alt_instr *begin; struct alt_instr *end; @@ -142,7 +144,6 @@ static void __apply_alternatives(void *a */ static int __apply_alternatives_multi_stop(void *unused) { - static int patched = 0; struct alt_region region = { .begin = (struct alt_instr *)__alt_instructions, .end = (struct alt_instr *)__alt_instructions_end, @@ -150,14 +151,14 @@ static int __apply_alternatives_multi_st
/* We always have a CPU 0 at this point (__init) */ if (smp_processor_id()) { - while (!READ_ONCE(patched)) + while (!READ_ONCE(alternatives_applied)) cpu_relax(); isb(); } else { - BUG_ON(patched); + BUG_ON(alternatives_applied); __apply_alternatives(®ion); /* Barriers provided by the cache flushing */ - WRITE_ONCE(patched, 1); + WRITE_ONCE(alternatives_applied, 1); }
return 0; --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -829,6 +829,22 @@ static int __init parse_kpti(char *str) early_param("kpti", parse_kpti); #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */
+static int cpu_copy_el2regs(void *__unused) +{ + /* + * Copy register values that aren't redirected by hardware. + * + * Before code patching, we only set tpidr_el1, all CPUs need to copy + * this value to tpidr_el2 before we patch the code. Once we've done + * that, freshly-onlined CPUs will set tpidr_el2, so we don't need to + * do anything here. + */ + if (!alternatives_applied) + write_sysreg(read_sysreg(tpidr_el1), tpidr_el2); + + return 0; +} + static const struct arm64_cpu_capabilities arm64_features[] = { { .desc = "GIC system register CPU interface", @@ -895,6 +911,7 @@ static const struct arm64_cpu_capabiliti .capability = ARM64_HAS_VIRT_HOST_EXTN, .def_scope = SCOPE_SYSTEM, .matches = runs_at_el2, + .enable = cpu_copy_el2regs, }, { .desc = "32-bit EL0 Support",