Re: [PATCH v3 05/16] perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv

Paolo Bonzini
2021-09-22T06:26:41Z

On 22/09/21 02:05, Sean Christopherson wrote:
> Drop "support" for guest callbacks from architctures that don't implement
> the guest callbacks. Future patches will convert the callbacks to
> static_call; rather than churn a bunch of arch code (that was presumably
> copy+pasted from x86), remove it wholesale as it's useless and at best
> wasting cycles.
>
> A future patch will also add a Kconfig to force architcture to opt into
> the callbacks to make it more difficult for uses "support" to sneak in in
> the future.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/arm/kernel/perf_callchain.c | 33 ++++-------------------------
> arch/csky/kernel/perf_callchain.c | 12 -----------
> arch/nds32/kernel/perf_event_cpu.c | 34 ++++--------------------------
> arch/riscv/kernel/perf_callchain.c | 13 ------------
> 4 files changed, 8 insertions(+), 84 deletions(-)
>
> diff --git a/arch/arm/kernel/perf_callchain.c b/arch/arm/kernel/perf_callchain.c
> index 1626dfc6f6ce..bc6b246ab55e 100644
> --- a/arch/arm/kernel/perf_callchain.c
> +++ b/arch/arm/kernel/perf_callchain.c
> @@ -62,14 +62,8 @@ user_backtrace(struct frame_tail __user *tail,
> void
> perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> struct frame_tail __user *tail;
>
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - /* We don't support guest os callchain now */
> - return;
> - }
> -
> perf_callchain_store(entry, regs->ARM_pc);
>
> if (!current->mm)
> @@ -99,44 +93,25 @@ callchain_trace(struct stackframe *fr,
> void
> perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> struct stackframe fr;
>
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - /* We don't support guest os callchain now */
> - return;
> - }
> -
> arm_get_current_stackframe(regs, &fr);
> walk_stackframe(&fr, callchain_trace, entry);
> }
>
> unsigned long perf_instruction_pointer(struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> -
> - if (guest_cbs && guest_cbs->is_in_guest())
> - return guest_cbs->get_guest_ip();
> -
> return instruction_pointer(regs);
> }
>
> unsigned long perf_misc_flags(struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> int misc = 0;
>
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - if (guest_cbs->is_user_mode())
> - misc |= PERF_RECORD_MISC_GUEST_USER;
> - else
> - misc |= PERF_RECORD_MISC_GUEST_KERNEL;
> - } else {
> - if (user_mode(regs))
> - misc |= PERF_RECORD_MISC_USER;
> - else
> - misc |= PERF_RECORD_MISC_KERNEL;
> - }
> + if (user_mode(regs))
> + misc |= PERF_RECORD_MISC_USER;
> + else
> + misc |= PERF_RECORD_MISC_KERNEL;
>
> return misc;
> }
> diff --git a/arch/csky/kernel/perf_callchain.c b/arch/csky/kernel/perf_callchain.c
> index 35318a635a5f..92057de08f4f 100644
> --- a/arch/csky/kernel/perf_callchain.c
> +++ b/arch/csky/kernel/perf_callchain.c
> @@ -86,13 +86,8 @@ static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
> void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
> struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> unsigned long fp = 0;
>
> - /* C-SKY does not support virtualization. */
> - if (guest_cbs && guest_cbs->is_in_guest())
> - return;
> -
> fp = regs->regs[4];
> perf_callchain_store(entry, regs->pc);
>
> @@ -111,15 +106,8 @@ void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
> void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
> struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> struct stackframe fr;
>
> - /* C-SKY does not support virtualization. */
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - pr_warn("C-SKY does not support perf in guest mode!");
> - return;
> - }
> -
> fr.fp = regs->regs[4];
> fr.lr = regs->lr;
> walk_stackframe(&fr, entry);
> diff --git a/arch/nds32/kernel/perf_event_cpu.c b/arch/nds32/kernel/perf_event_cpu.c
> index f38791960781..a78a879e7ef1 100644
> --- a/arch/nds32/kernel/perf_event_cpu.c
> +++ b/arch/nds32/kernel/perf_event_cpu.c
> @@ -1363,7 +1363,6 @@ void
> perf_callchain_user(struct perf_callchain_entry_ctx *entry,
> struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> unsigned long fp = 0;
> unsigned long gp = 0;
> unsigned long lp = 0;
> @@ -1372,11 +1371,6 @@ perf_callchain_user(struct perf_callchain_entry_ctx *entry,
>
> leaf_fp = 0;
>
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - /* We don't support guest os callchain now */
> - return;
> - }
> -
> perf_callchain_store(entry, regs->ipc);
> fp = regs->fp;
> gp = regs->gp;
> @@ -1480,13 +1474,8 @@ void
> perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
> struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> struct stackframe fr;
>
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - /* We don't support guest os callchain now */
> - return;
> - }
> fr.fp = regs->fp;
> fr.lp = regs->lp;
> fr.sp = regs->sp;
> @@ -1495,32 +1484,17 @@ perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
>
> unsigned long perf_instruction_pointer(struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> -
> - /* However, NDS32 does not support virtualization */
> - if (guest_cbs && guest_cbs->is_in_guest())
> - return guest_cbs->get_guest_ip();
> -
> return instruction_pointer(regs);
> }
>
> unsigned long perf_misc_flags(struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> int misc = 0;
>
> - /* However, NDS32 does not support virtualization */
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - if (guest_cbs->is_user_mode())
> - misc |= PERF_RECORD_MISC_GUEST_USER;
> - else
> - misc |= PERF_RECORD_MISC_GUEST_KERNEL;
> - } else {
> - if (user_mode(regs))
> - misc |= PERF_RECORD_MISC_USER;
> - else
> - misc |= PERF_RECORD_MISC_KERNEL;
> - }
> + if (user_mode(regs))
> + misc |= PERF_RECORD_MISC_USER;
> + else
> + misc |= PERF_RECORD_MISC_KERNEL;
>
> return misc;
> }
> diff --git a/arch/riscv/kernel/perf_callchain.c b/arch/riscv/kernel/perf_callchain.c
> index 8ecfc4c128bc..1fc075b8f764 100644
> --- a/arch/riscv/kernel/perf_callchain.c
> +++ b/arch/riscv/kernel/perf_callchain.c
> @@ -56,13 +56,8 @@ static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
> void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
> struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> unsigned long fp = 0;
>
> - /* RISC-V does not support perf in guest mode. */
> - if (guest_cbs && guest_cbs->is_in_guest())
> - return;
> -
> fp = regs->s0;
> perf_callchain_store(entry, regs->epc);
>
> @@ -79,13 +74,5 @@ static bool fill_callchain(void *entry, unsigned long pc)
> void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
> struct pt_regs *regs)
> {
> - struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
> -
> - /* RISC-V does not support perf in guest mode. */
> - if (guest_cbs && guest_cbs->is_in_guest()) {
> - pr_warn("RISC-V does not support perf in guest mode!");
> - return;
> - }
> -
> walk_stackframe(NULL, regs, fill_callchain, entry);
> }
>

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>