On Tue, Aug 08, 2017 at 05:46:09PM +0100, James Morse wrote:
> 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@xxxxxxx>
> ---
> Changes since v1:
> * cpu_copy_el2regs()'s 'have I been patched' test now always sets a register,
> just in case the compiler puts do_copyregs on the stack.
I don't understand this?
>
> arch/arm64/include/asm/assembler.h | 8 ++++++++
> arch/arm64/include/asm/percpu.h | 11 +++++++++--
> arch/arm64/include/asm/processor.h | 1 +
> arch/arm64/kernel/cpufeature.c | 23 +++++++++++++++++++++++
> arch/arm64/mm/proc.S | 8 ++++++++
> 5 files changed, 49 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
> index 1b67c3782d00..06252602901e 100644
> --- a/arch/arm64/include/asm/assembler.h
> +++ b/arch/arm64/include/asm/assembler.h
> @@ -236,7 +236,11 @@ 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
>
> @@ -247,7 +251,11 @@ 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
>
> diff --git a/arch/arm64/include/asm/percpu.h b/arch/arm64/include/asm/percpu.h
> index 3bd498e4de4c..43393208229e 100644
> --- a/arch/arm64/include/asm/percpu.h
> +++ b/arch/arm64/include/asm/percpu.h
> @@ -16,11 +16,15 @@
> #ifndef __ASM_PERCPU_H
> #define __ASM_PERCPU_H
>
> +#include <asm/alternative.h>
> #include <asm/stack_pointer.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)
> @@ -31,7 +35,10 @@ static inline unsigned long __my_cpu_offset(void)
> * 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;
> diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h
> index 64c9e78f9882..6d4fdfccf869 100644
> --- a/arch/arm64/include/asm/processor.h
> +++ b/arch/arm64/include/asm/processor.h
> @@ -193,5 +193,6 @@ static inline void spin_lock_prefetch(const void *ptr)
>
> int cpu_enable_pan(void *__unused);
> int cpu_enable_cache_maint_trap(void *__unused);
> +int cpu_copy_el2regs(void *__unused);
>
> #endif /* __ASM_PROCESSOR_H */
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index 9f9e0064c8c1..1960706d2422 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -864,6 +864,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
> .capability = ARM64_HAS_VIRT_HOST_EXTN,
> .def_scope = SCOPE_SYSTEM,
> .matches = runs_at_el2,
> + .enable = cpu_copy_el2regs,
> },
> {
> .desc = "32-bit EL0 Support",
> @@ -1295,3 +1296,25 @@ static int __init enable_mrs_emulation(void)
> }
>
> late_initcall(enable_mrs_emulation);
> +
> +int cpu_copy_el2regs(void *__unused)
> +{
> + int do_copyregs = 0;
> +
> + /*
> + * 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.
> + */
> + asm volatile(ALTERNATIVE("mov %0, #1", "mov %0, #0",
> + ARM64_HAS_VIRT_HOST_EXTN)
> + : "=r" (do_copyregs) : : );
> +
> + if (do_copyregs)
> + write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
Could you just use has_vhe() here ?
> +
> + return 0;
> +}
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index 877d42fb0df6..109d43a15aaf 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -70,7 +70,11 @@ ENTRY(cpu_do_suspend)
> mrs x8, mdscr_el1
> mrs x9, oslsr_el1
> mrs x10, sctlr_el1
> +alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
> mrs x11, tpidr_el1
> +alternative_else
> + mrs x11, tpidr_el2
> +alternative_endif
> mrs x12, sp_el0
> stp x2, x3, [x0]
> stp x4, xzr, [x0, #16]
> @@ -116,7 +120,11 @@ ENTRY(cpu_do_resume)
> msr mdscr_el1, x10
>
> msr sctlr_el1, x12
> +alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
> msr tpidr_el1, x13
> +alternative_else
> + msr tpidr_el2, x13
> +alternative_endif
> msr sp_el0, x14
> /*
> * Restore oslsr_el1 by writing oslar_el1
> --
> 2.13.3
>
Otherwise:
Reviewed-by: Christoffer Dall <cdall@xxxxxxxxxx>
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