| Message ID | 20230724172844.690165660@linutronix.de (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | x86/cpu: Rework the topology evaluation | expand |
On Mon, Jul 24, 2023 at 07:44:17PM +0200, Thomas Gleixner wrote: > +static inline bool topo_subleaf(struct topo_scan *tscan, u32 leaf, u32 subleaf) > +{ > + unsigned int dom, maxtype = leaf == 0xb ? CORE_TYPE + 1 : MAX_TYPE; > + struct { > + // eax > + u32 x2apic_shift : 5, // Number of bits to shift APIC ID right > + // for the topology ID at the next level > + __rsvd0 : 27; // Reserved > + // ebx > + u32 num_processors : 16, // Number of processors at current level > + __rsvd1 : 16; // Reserved > + // ecx > + u32 level : 8, // Current topology level. Same as sub leaf number > + type : 8, // Level type. If 0, invalid > + __rsvd2 : 16; // Reserved > + // edx > + u32 x2apic_id : 32; // X2APIC ID of the current logical processor That comment seems inconsistent, either have then all aligned or move all register names left. But yeah, I think this is more or less what we ended up with last time I went through this. > + } sl; > + > + cpuid_subleaf(leaf, subleaf, &sl); > + > + if (!sl.num_processors || sl.type == INVALID_TYPE) > + return false; > + > + if (sl.type >= maxtype) { > + /* > + * As the subleafs are ordered in domain level order, this > + * could be recovered in theory by propagating the > + * information at the last parsed level. > + * > + * But if the infinite wisdom of hardware folks decides to > + * create a new domain type between CORE and MODULE or DIE > + * and DIEGRP, then that would overwrite the CORE or DIE > + * information. > + * > + * It really would have been too obvious to make the domain > + * type space sparse and leave a few reserved types between > + * the points which might change instead of forcing > + * software to either create a monstrosity of workarounds > + * or just being up the creek without a paddle. > + * > + * Refuse to implement monstrosity, emit an error and try > + * to survive. > + */ > + pr_err_once("Topology: leaf 0x%x:%d Unknown domain type %u\n", > + leaf, subleaf, sl.type); > + return true; > + } > + > + dom = topo_domain_map[sl.type]; > + if (!dom) { > + tscan->c->topo.initial_apicid = sl.x2apic_id; > + } else if (tscan->c->topo.initial_apicid != sl.x2apic_id) { > + pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf %d APIC ID mismatch %x != %x\n", > + leaf, subleaf, tscan->c->topo.initial_apicid, sl.x2apic_id); > + } > + > + topology_set_dom(tscan, dom, sl.x2apic_shift, sl.num_processors); > + return true; > +} > + > +static bool parse_topology_leaf(struct topo_scan *tscan, u32 leaf) > +{ > + u32 subleaf; > + > + if (tscan->c->cpuid_level < leaf) > + return false; > + > + /* Read all available subleafs and populate the levels */ > + for (subleaf = 0; topo_subleaf(tscan, leaf, subleaf); subleaf++); Personally I prefer: for (;;) ; that is, have the semicolon on it's own line, but meh. > + > + /* If subleaf 0 failed to parse, give up */ > + if (!subleaf) > + return false; > + > + /* > + * There are machines in the wild which have shift 0 in the subleaf > + * 0, but advertise 2 logical processors at that level. They are > + * truly SMT. > + */ > + if (!tscan->dom_shifts[TOPO_SMT_DOMAIN] && tscan->dom_ncpus[TOPO_SMT_DOMAIN] > 1) { > + u16 sft = get_count_order(tscan->dom_ncpus[TOPO_SMT_DOMAIN]); > + > + pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf 0 has shift level 0 but %u CPUs\n", > + leaf, tscan->dom_ncpus[TOPO_SMT_DOMAIN]); > + topology_update_dom(tscan, TOPO_SMT_DOMAIN, sft, tscan->dom_ncpus[TOPO_SMT_DOMAIN]); > + } > + > + set_cpu_cap(tscan->c, X86_FEATURE_XTOPOLOGY); > + return true; > +} > + > +bool cpu_parse_topology_ext(struct topo_scan *tscan) > +{ > + /* Try lead 0x1F first. If not available try leaf 0x0b */ > + if (parse_topology_leaf(tscan, 0x1f)) > + return true; > + return parse_topology_leaf(tscan, 0x0b); > +} >
On Mon, Jul 24, 2023 at 10:49:42PM +0200, Peter Zijlstra wrote: > On Mon, Jul 24, 2023 at 07:44:17PM +0200, Thomas Gleixner wrote: > > > +static inline bool topo_subleaf(struct topo_scan *tscan, u32 leaf, u32 subleaf) > > +{ > > + unsigned int dom, maxtype = leaf == 0xb ? CORE_TYPE + 1 : MAX_TYPE; > > + struct { > > + // eax > > + u32 x2apic_shift : 5, // Number of bits to shift APIC ID right > > + // for the topology ID at the next level > > + __rsvd0 : 27; // Reserved > > + // ebx > > + u32 num_processors : 16, // Number of processors at current level > > + __rsvd1 : 16; // Reserved > > + // ecx > > + u32 level : 8, // Current topology level. Same as sub leaf number > > + type : 8, // Level type. If 0, invalid > > + __rsvd2 : 16; // Reserved > > + // edx > > + u32 x2apic_id : 32; // X2APIC ID of the current logical processor > > That comment seems inconsistent, either have then all aligned or move > all register names left. AMD code seems to have the reg names left aligned -- perhaps do the same here.
On Mon, Jul 24 2023 at 22:49, Peter Zijlstra wrote: > On Mon, Jul 24, 2023 at 07:44:17PM +0200, Thomas Gleixner wrote: > >> +static inline bool topo_subleaf(struct topo_scan *tscan, u32 leaf, u32 subleaf) >> +{ >> + unsigned int dom, maxtype = leaf == 0xb ? CORE_TYPE + 1 : MAX_TYPE; >> + struct { >> + // eax >> + u32 x2apic_shift : 5, // Number of bits to shift APIC ID right >> + // for the topology ID at the next level >> + __rsvd0 : 27; // Reserved >> + // ebx >> + u32 num_processors : 16, // Number of processors at current level >> + __rsvd1 : 16; // Reserved >> + // ecx >> + u32 level : 8, // Current topology level. Same as sub leaf number >> + type : 8, // Level type. If 0, invalid >> + __rsvd2 : 16; // Reserved >> + // edx >> + u32 x2apic_id : 32; // X2APIC ID of the current logical processor > > That comment seems inconsistent, either have then all aligned or move > all register names left. Bah. I had all the register names left at some point. No idea how I lost that again. Probably when I rolled back to some earlier version after screwing up :) >> + >> + /* Read all available subleafs and populate the levels */ >> + for (subleaf = 0; topo_subleaf(tscan, leaf, subleaf); subleaf++); > > Personally I prefer: > > for (;;) > ; > > that is, have the semicolon on it's own line, but meh. :)
--- a/arch/x86/kernel/cpu/Makefile +++ b/arch/x86/kernel/cpu/Makefile @@ -18,7 +18,7 @@ KMSAN_SANITIZE_common.o := n KCSAN_SANITIZE_common.o := n obj-y := cacheinfo.o scattered.o -obj-y += topology_common.o topology.o +obj-y += topology_common.o topology_ext.o topology.o obj-y += common.o obj-y += rdrand.o obj-y += match.o --- a/arch/x86/kernel/cpu/topology.h +++ b/arch/x86/kernel/cpu/topology.h @@ -16,6 +16,7 @@ void cpu_init_topology(struct cpuinfo_x8 void cpu_parse_topology(struct cpuinfo_x86 *c); void topology_set_dom(struct topo_scan *tscan, enum x86_topology_domains dom, unsigned int shift, unsigned int ncpus); +bool cpu_parse_topology_ext(struct topo_scan *tscan); static inline u16 topo_shift_apicid(u16 apicid, enum x86_topology_domains dom) { @@ -31,4 +32,15 @@ static inline u16 topo_relative_domain_i return apicid & (x86_topo_system.dom_size[dom] - 1); } +/* + * Update a domain level after the fact without propagating. Used to fixup + * broken CPUID enumerations. + */ +static inline void topology_update_dom(struct topo_scan *tscan, enum x86_topology_domains dom, + unsigned int shift, unsigned int ncpus) +{ + tscan->dom_shifts[dom] = shift; + tscan->dom_ncpus[dom] = ncpus; +} + #endif /* ARCH_X86_TOPOLOGY_H */ --- /dev/null +++ b/arch/x86/kernel/cpu/topology_ext.c @@ -0,0 +1,136 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/cpu.h> + +#include <asm/apic.h> +#include <asm/memtype.h> +#include <asm/processor.h> + +#include "cpu.h" + +enum topo_types { + INVALID_TYPE = 0, + SMT_TYPE = 1, + CORE_TYPE = 2, + MODULE_TYPE = 3, + TILE_TYPE = 4, + DIE_TYPE = 5, + DIEGRP_TYPE = 6, + MAX_TYPE = 7, +}; + +/* + * Use a lookup table for the case that there are future types > 6 which + * describe an intermediate domain level which does not exist today. + * + * A table will also be handy to parse the new AMD 0x80000026 leaf which + * has defined different domain types, but otherwise uses the same layout + * with some of the reserved bits used for new information. + */ +static const unsigned int topo_domain_map[MAX_TYPE] = { + [SMT_TYPE] = TOPO_SMT_DOMAIN, + [CORE_TYPE] = TOPO_CORE_DOMAIN, + [MODULE_TYPE] = TOPO_MODULE_DOMAIN, + [TILE_TYPE] = TOPO_TILE_DOMAIN, + [DIE_TYPE] = TOPO_DIE_DOMAIN, + [DIEGRP_TYPE] = TOPO_PKG_DOMAIN, +}; + +static inline bool topo_subleaf(struct topo_scan *tscan, u32 leaf, u32 subleaf) +{ + unsigned int dom, maxtype = leaf == 0xb ? CORE_TYPE + 1 : MAX_TYPE; + struct { + // eax + u32 x2apic_shift : 5, // Number of bits to shift APIC ID right + // for the topology ID at the next level + __rsvd0 : 27; // Reserved + // ebx + u32 num_processors : 16, // Number of processors at current level + __rsvd1 : 16; // Reserved + // ecx + u32 level : 8, // Current topology level. Same as sub leaf number + type : 8, // Level type. If 0, invalid + __rsvd2 : 16; // Reserved + // edx + u32 x2apic_id : 32; // X2APIC ID of the current logical processor + } sl; + + cpuid_subleaf(leaf, subleaf, &sl); + + if (!sl.num_processors || sl.type == INVALID_TYPE) + return false; + + if (sl.type >= maxtype) { + /* + * As the subleafs are ordered in domain level order, this + * could be recovered in theory by propagating the + * information at the last parsed level. + * + * But if the infinite wisdom of hardware folks decides to + * create a new domain type between CORE and MODULE or DIE + * and DIEGRP, then that would overwrite the CORE or DIE + * information. + * + * It really would have been too obvious to make the domain + * type space sparse and leave a few reserved types between + * the points which might change instead of forcing + * software to either create a monstrosity of workarounds + * or just being up the creek without a paddle. + * + * Refuse to implement monstrosity, emit an error and try + * to survive. + */ + pr_err_once("Topology: leaf 0x%x:%d Unknown domain type %u\n", + leaf, subleaf, sl.type); + return true; + } + + dom = topo_domain_map[sl.type]; + if (!dom) { + tscan->c->topo.initial_apicid = sl.x2apic_id; + } else if (tscan->c->topo.initial_apicid != sl.x2apic_id) { + pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf %d APIC ID mismatch %x != %x\n", + leaf, subleaf, tscan->c->topo.initial_apicid, sl.x2apic_id); + } + + topology_set_dom(tscan, dom, sl.x2apic_shift, sl.num_processors); + return true; +} + +static bool parse_topology_leaf(struct topo_scan *tscan, u32 leaf) +{ + u32 subleaf; + + if (tscan->c->cpuid_level < leaf) + return false; + + /* Read all available subleafs and populate the levels */ + for (subleaf = 0; topo_subleaf(tscan, leaf, subleaf); subleaf++); + + /* If subleaf 0 failed to parse, give up */ + if (!subleaf) + return false; + + /* + * There are machines in the wild which have shift 0 in the subleaf + * 0, but advertise 2 logical processors at that level. They are + * truly SMT. + */ + if (!tscan->dom_shifts[TOPO_SMT_DOMAIN] && tscan->dom_ncpus[TOPO_SMT_DOMAIN] > 1) { + u16 sft = get_count_order(tscan->dom_ncpus[TOPO_SMT_DOMAIN]); + + pr_warn_once(FW_BUG "CPUID leaf 0x%x subleaf 0 has shift level 0 but %u CPUs\n", + leaf, tscan->dom_ncpus[TOPO_SMT_DOMAIN]); + topology_update_dom(tscan, TOPO_SMT_DOMAIN, sft, tscan->dom_ncpus[TOPO_SMT_DOMAIN]); + } + + set_cpu_cap(tscan->c, X86_FEATURE_XTOPOLOGY); + return true; +} + +bool cpu_parse_topology_ext(struct topo_scan *tscan) +{ + /* Try lead 0x1F first. If not available try leaf 0x0b */ + if (parse_topology_leaf(tscan, 0x1f)) + return true; + return parse_topology_leaf(tscan, 0x0b); +}
detect_extended_topology() along with it's early() variant is a classic example for duct tape engineering: - It evaluates an array of subleafs with a boatload of local variables for the relevant topology levels instead of using an array to save the enumerated information and propagate it to the right level - It has no boundary checks for subleafs - It prevents updating the die_id with a crude workaround instead of checking for leaf 0xb which does not provide die information. - It's broken vs. the number of dies evaluation as it uses: num_processors[DIE_LEVEL] / num_processors[CORE_LEVEL] which "works" only correctly if there is none of the intermediate topology levels (MODULE/TILE) enumerated. There is zero value in trying to "fix" that code as the only proper fix is to rewrite it from scratch. Implement a sane parser with proper code documentation, which will be used for the consolidated topology evaluation in the next step. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- arch/x86/kernel/cpu/Makefile | 2 arch/x86/kernel/cpu/topology.h | 12 +++ arch/x86/kernel/cpu/topology_ext.c | 136 +++++++++++++++++++++++++++++++++++++ 3 files changed, 149 insertions(+), 1 deletion(-)