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Date: Fri, 29 Apr 2016 09:40:09 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Mike Travis <travis@....com>
Cc: Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Len Brown <len.brown@...el.com>,
Dimitri Sivanich <sivanich@....com>,
Russ Anderson <rja@....com>,
John Estabrook <estabrook@....com>,
Andrew Banman <abanman@....com>,
Nathan Zimmer <nzimmer@....com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/21] X86_64, UV: Enable/Disable UV1 only workaround code
* Mike Travis <travis@....com> wrote:
> This patch allows enabling or disabling of the "EXTRA APIC ID BITS"
> workaround found only on UV100/UV1000 systems. This workaround was
> required by the Intel Nahelm Processor (used in that architecture)
> because it could only support a limited number of CPU threads within
> the SSI. This was due to only having 8 APIC ID bits thus a workaround
> was added to add and remove extra bits to the APIC ID. It also required
> a specialized UV1 only apic driver.
>
> Signed-off-by: Mike Travis <travis@....com>
> Tested-by: Nathan Zimmer <nzimmer@....com>
> ---
> arch/x86/Kconfig | 14 ++++++++++++++
> arch/x86/include/asm/uv/uv_hub.h | 11 ++++-------
> arch/x86/include/asm/uv/uv_mmrs.h | 2 ++
> arch/x86/kernel/apic/x2apic_uv_x.c | 26 +++++++++++++++++++++++---
> 4 files changed, 43 insertions(+), 10 deletions(-)
>
> --- linux.orig/arch/x86/Kconfig
> +++ linux/arch/x86/Kconfig
> @@ -489,6 +489,20 @@ config X86_UV
> This option is needed in order to support SGI Ultraviolet systems.
> If you don't have one of these, you should say N here.
>
> +config X86_UV1_SUPPORTED
> + bool "SGI Ultraviolet Series 1 Supported"
> + depends on X86_UV
> + default n
> + ---help---
> + Set this option if you have a UV100/UV1000 system. By setting
> + this option extra execution time and space is introduced for
> + workarounds designed for processors limited to only 8 apicid bits.
> + This limited the number of processors that could be supported in
> + an SSI. With the Intel release of the SandyBridge Processor (used
> + in UV2000 systems), the "x2apic" mode was introduced to extend
> + the number of apicid bits. Thus more processors are supported
> + without these workarounds and the specialized UV1 only apic driver.
> +
> # Following is an alphabetically sorted list of 32 bit extended platforms
> # Please maintain the alphabetic order if and when there are additions
>
> --- linux.orig/arch/x86/include/asm/uv/uv_hub.h
> +++ linux/arch/x86/include/asm/uv/uv_hub.h
> @@ -289,25 +289,21 @@ union uvh_apicid {
> #define UV4_GLOBAL_MMR32_SIZE (16UL * 1024 * 1024)
>
> #define UV_LOCAL_MMR_BASE ( \
> - is_uv1_hub() ? UV1_LOCAL_MMR_BASE : \
> is_uv2_hub() ? UV2_LOCAL_MMR_BASE : \
> is_uv3_hub() ? UV3_LOCAL_MMR_BASE : \
> /*is_uv4_hub*/ UV4_LOCAL_MMR_BASE)
>
> #define UV_GLOBAL_MMR32_BASE ( \
> - is_uv1_hub() ? UV1_GLOBAL_MMR32_BASE : \
> is_uv2_hub() ? UV2_GLOBAL_MMR32_BASE : \
> is_uv3_hub() ? UV3_GLOBAL_MMR32_BASE : \
> /*is_uv4_hub*/ UV4_GLOBAL_MMR32_BASE)
>
> #define UV_LOCAL_MMR_SIZE ( \
> - is_uv1_hub() ? UV1_LOCAL_MMR_SIZE : \
> is_uv2_hub() ? UV2_LOCAL_MMR_SIZE : \
> is_uv3_hub() ? UV3_LOCAL_MMR_SIZE : \
> /*is_uv4_hub*/ UV4_LOCAL_MMR_SIZE)
>
> #define UV_GLOBAL_MMR32_SIZE ( \
> - is_uv1_hub() ? UV1_GLOBAL_MMR32_SIZE : \
> is_uv2_hub() ? UV2_GLOBAL_MMR32_SIZE : \
> is_uv3_hub() ? UV3_GLOBAL_MMR32_SIZE : \
> /*is_uv4_hub*/ UV4_GLOBAL_MMR32_SIZE)
Hm, are you sure this can be removed?
> @@ -445,9 +441,6 @@ static inline int uv_apicid_to_pnode(int
> */
> static inline int uv_apicid_to_socket(int apicid)
> {
> - if (is_uv1_hub())
> - return (apicid >> (uv_hub_info->apic_pnode_shift - 1)) & 1;
> - else
> return 0;
> }
>
> @@ -704,7 +697,11 @@ static inline void uv_set_cpu_scir_bits(
> }
> }
>
> +#ifdef UV1_HUB_IS_SUPPORTED
> extern unsigned int uv_apicid_hibits;
> +#else
> +#define uv_apicid_hibits 0
> +#endif
> static unsigned long uv_hub_ipi_value(int apicid, int vector, int mode)
> {
> apicid |= uv_apicid_hibits;
> --- linux.orig/arch/x86/include/asm/uv/uv_mmrs.h
> +++ linux/arch/x86/include/asm/uv/uv_mmrs.h
> @@ -95,7 +95,9 @@
> #define UV4_HUB_PART_NUMBER 0x99a1
>
> /* Compat: Indicate which UV Hubs are supported. */
> +#ifdef CONFIG_X86_UV1_SUPPORTED
> #define UV1_HUB_IS_SUPPORTED 1
> +#endif
> #define UV2_HUB_IS_SUPPORTED 1
> #define UV3_HUB_IS_SUPPORTED 1
> #define UV4_HUB_IS_SUPPORTED 1
> --- linux.orig/arch/x86/kernel/apic/x2apic_uv_x.c
> +++ linux/arch/x86/kernel/apic/x2apic_uv_x.c
> @@ -39,7 +39,9 @@
> #include <asm/x86_init.h>
> #include <asm/nmi.h>
>
> +#ifdef UV1_HUB_IS_SUPPORTED
> DEFINE_PER_CPU(int, x2apic_extra_bits);
> +#endif
>
> #define PR_DEVEL(fmt, args...) pr_devel("%s: " fmt, __func__, args)
>
> @@ -50,8 +52,10 @@ static u64 gru_dist_lmask, gru_dist_umas
> static union uvh_apicid uvh_apicid;
> int uv_min_hub_revision_id;
> EXPORT_SYMBOL_GPL(uv_min_hub_revision_id);
> +#ifdef UV1_HUB_IS_SUPPORTED
> unsigned int uv_apicid_hibits;
> EXPORT_SYMBOL_GPL(uv_apicid_hibits);
> +#endif
>
> static struct apic apic_x2apic_uv_x;
>
> @@ -145,6 +149,7 @@ static void __init early_get_apic_pnode_
> * interrupts potentially passing through the UV HUB. This prevents
> * a deadlock between interrupts and IO port operations.
> */
> +#ifdef UV1_HUB_IS_SUPPORTED
> static void __init uv_set_apicid_hibit(void)
> {
> union uv1h_lb_target_physical_apic_id_mask_u apicid_mask;
> @@ -156,6 +161,7 @@ static void __init uv_set_apicid_hibit(v
> apicid_mask.s1.bit_enables & UV_APICID_HIBIT_MASK;
> }
> }
> +#endif
>
> static int __init uv_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
> {
> @@ -190,13 +196,14 @@ static int __init uv_acpi_madt_oem_check
> uv_system_type = UV_X2APIC;
> uv_apic = 0;
>
> +#ifdef UV1_HUB_IS_SUPPORTED
> } else if (!strcmp(oem_table_id, "UVH")) { /* only UV1 systems */
> uv_system_type = UV_NON_UNIQUE_APIC;
> __this_cpu_write(x2apic_extra_bits,
> pnodeid << uvh_apicid.s.pnode_shift);
> uv_set_apicid_hibit();
> uv_apic = 1;
> -
> +#endif
> } else if (!strcmp(oem_table_id, "UVL")) { /* only used for */
> uv_system_type = UV_LEGACY_APIC; /* very small systems */
> uv_apic = 0;
> @@ -252,7 +259,6 @@ static int uv_wakeup_secondary(int phys_
> int pnode;
>
> pnode = uv_apicid_to_pnode(phys_apicid);
> - phys_apicid |= uv_apicid_hibits;
> val = (1UL << UVH_IPI_INT_SEND_SHFT) |
> (phys_apicid << UVH_IPI_INT_APIC_ID_SHFT) |
> ((start_rip << UVH_IPI_INT_VECTOR_SHFT) >> 12) |
> @@ -344,7 +350,7 @@ uv_cpu_mask_to_apicid_and(const struct c
> }
>
> if (likely(cpu < nr_cpu_ids)) {
> - *apicid = per_cpu(x86_cpu_to_apicid, cpu) | uv_apicid_hibits;
> + *apicid = per_cpu(x86_cpu_to_apicid, cpu);
> return 0;
> }
>
> @@ -353,21 +359,29 @@ uv_cpu_mask_to_apicid_and(const struct c
>
> static unsigned int x2apic_get_apic_id(unsigned long x)
> {
> +#ifdef UV1_HUB_IS_SUPPORTED
> unsigned int id;
>
> WARN_ON(preemptible() && num_online_cpus() > 1);
> id = x | __this_cpu_read(x2apic_extra_bits);
>
> return id;
> +#else
> + return x;
> +#endif
> }
>
> static unsigned long set_apic_id(unsigned int id)
> {
> +#ifdef UV1_HUB_IS_SUPPORTED
> unsigned long x;
>
> /* maskout x2apic_extra_bits ? */
> x = id;
> return x;
> +#else
> + return id;
> +#endif
> }
Hm, this hunk does not appear to be doing anything.
>
> static unsigned int uv_read_apic_id(void)
> @@ -442,10 +456,16 @@ static struct apic __refdata apic_x2apic
> .safe_wait_icr_idle = native_safe_x2apic_wait_icr_idle,
> };
>
> +#ifdef UV1_HUB_IS_SUPPORTED
> static void set_x2apic_extra_bits(int pnode)
> {
> __this_cpu_write(x2apic_extra_bits, pnode << uvh_apicid.s.pnode_shift);
> }
> +#else
> +static inline void set_x2apic_extra_bits(int pnode)
> +{
> +}
> +#endif
So Kconfig values and #ifdefs are not really user friendly nor developer friendly.
Wouldn't it be possible to eliminate all the #ifdefs and simply use something like
this:
static void set_x2apic_extra_bits(int pnode)
{
if (unlikely(uv_apic))
__this_cpu_write(x2apic_extra_bits, pnode << uvh_apicid.s.pnode_shift);
}
etc. The unlikely() will make sure this never impacts any fast path. You can also
mark 'uv_apic' with __read_mostly, to make sure it's nicely cached.
(You could also rename 'uv_apic' to 'legacy_uv1_apic' to make it really clear that
this is only for older systems.)
Hm?
Thanks,
Ingo
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