Re: [PATCH] x86/UV: GRU distributed mode mappings

[Dimitri Sivanich <sivanich@sgi.com>]

On Tue, May 28, 2013 at 09:59:12AM +0200, Ingo Molnar wrote:
> 
> * Dimitri Sivanich <sivanich@sgi.com> wrote:
> 
> > Setup mappings for GRU distributed mode and include them as untracked
> > pat ranges.
> 
> Would be nice to have the customary changelog content:
> 
>   " Current code does (A), this has a problem when (B).
>     We can improve this doing (C), because (D)."
> 
> Or so - your changelog is pretty light on the 'why' aspect.
>
How about the following?


UV GRU hardware will support an optional distributed mode that will allow 
per-node address mapping of local GRU space, as opposed to mapping all GRU
hardware to the same contiguous high space.

If GRU distributed mode is selected, setup per-node page table mappings and
include them as untracked pat ranges.

Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
---
 arch/x86/kernel/apic/x2apic_uv_x.c |   63 +++++++++++++++++++++++++++++----
 1 file changed, 57 insertions(+), 6 deletions(-)

Index: linux/arch/x86/kernel/apic/x2apic_uv_x.c
===================================================================
--- linux.orig/arch/x86/kernel/apic/x2apic_uv_x.c
+++ linux/arch/x86/kernel/apic/x2apic_uv_x.c
@@ -51,6 +51,8 @@ DEFINE_PER_CPU(int, x2apic_extra_bits);
 
 static enum uv_system_type uv_system_type;
 static u64 gru_start_paddr, gru_end_paddr;
+static u64 gru_dist_base, gru_first_node_paddr = -1LL, gru_last_node_paddr;
+static u64 gru_dist_lmask, gru_dist_umask;
 static union uvh_apicid uvh_apicid;
 int uv_min_hub_revision_id;
 EXPORT_SYMBOL_GPL(uv_min_hub_revision_id);
@@ -72,7 +74,19 @@ static unsigned long __init uv_early_rea
 
 static inline bool is_GRU_range(u64 start, u64 end)
 {
-	return start >= gru_start_paddr && end <= gru_end_paddr;
+	if (gru_dist_base) {
+		u64 su = start & gru_dist_umask; /* upper (incl pnode) bits */
+		u64 sl = start & gru_dist_lmask; /* base offset bits */
+		u64 eu = end & gru_dist_umask;
+		u64 el = end & gru_dist_lmask;
+
+		/* Must reside completely within a single GRU range */
+		return (sl == gru_dist_base && el == gru_dist_base &&
+			su >= gru_first_node_paddr &&
+			su <= gru_last_node_paddr &&
+			eu == su);
+	} else
+		return start >= gru_start_paddr && end <= gru_end_paddr;
 }
 
 static bool uv_is_untracked_pat_range(u64 start, u64 end)
@@ -470,19 +484,56 @@ static __init void map_high(char *id, un
 		init_extra_mapping_wb(paddr, bytes);
 }
 
+static __init void map_gru_distributed(unsigned long c)
+{
+	union uvh_rh_gam_gru_overlay_config_mmr_u gru;
+	u64 paddr;
+	unsigned long bytes;
+	int nid;
+
+	gru.v = c;
+	/* only base bits 42:28 relevant in dist mode */
+	gru_dist_base = gru.v & 0x000007fff0000000UL;
+	if (!gru_dist_base) {
+		pr_info("UV: Map GRU_DIST base address NULL\n");
+		return;
+	}
+	bytes = 1UL << UVH_RH_GAM_GRU_OVERLAY_CONFIG_MMR_BASE_SHFT;
+	gru_dist_lmask = ((1UL << uv_hub_info->m_val) - 1) & ~(bytes - 1);
+	gru_dist_umask = ~((1UL << uv_hub_info->m_val) - 1);
+	gru_dist_base &= gru_dist_lmask; /* Clear bits above M */
+	for_each_online_node(nid) {
+		paddr = ((u64)uv_node_to_pnode(nid) << uv_hub_info->m_val) |
+				gru_dist_base;
+		init_extra_mapping_wb(paddr, bytes);
+		gru_first_node_paddr = min(paddr, gru_first_node_paddr);
+		gru_last_node_paddr = max(paddr, gru_last_node_paddr);
+	}
+	/* Save upper (63:M) bits of address only for is_GRU_range */
+	gru_first_node_paddr &= gru_dist_umask;
+	gru_last_node_paddr &= gru_dist_umask;
+	pr_info("UV: Map GRU_DIST base 0x%016llx  0x%016llx - 0x%016llx\n",
+		gru_dist_base, gru_first_node_paddr, gru_last_node_paddr);
+}
+
 static __init void map_gru_high(int max_pnode)
 {
 	union uvh_rh_gam_gru_overlay_config_mmr_u gru;
 	int shift = UVH_RH_GAM_GRU_OVERLAY_CONFIG_MMR_BASE_SHFT;
 
 	gru.v = uv_read_local_mmr(UVH_RH_GAM_GRU_OVERLAY_CONFIG_MMR);
-	if (gru.s.enable) {
-		map_high("GRU", gru.s.base, shift, shift, max_pnode, map_wb);
-		gru_start_paddr = ((u64)gru.s.base << shift);
-		gru_end_paddr = gru_start_paddr + (1UL << shift) * (max_pnode + 1);
-	} else {
+	if (!gru.s.enable) {
 		pr_info("UV: GRU disabled\n");
+		return;
+	}
+
+	if (is_uv3_hub() && gru.s3.mode) {
+		map_gru_distributed(gru.v);
+		return;
 	}
+	map_high("GRU", gru.s.base, shift, shift, max_pnode, map_wb);
+	gru_start_paddr = ((u64)gru.s.base << shift);
+	gru_end_paddr = gru_start_paddr + (1UL << shift) * (max_pnode + 1);
 }
 
 static __init void map_mmr_high(int max_pnode)