[Patch 2/2] Kexec/Kdump support - POWER6

["Sachin P. Sant" <sachinp@in.ibm.com>]

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On Power machines supporting VRMA, Kexec/Kdump does not work.
Hypervisor stores VRMA mapping used by the OS, in the hpte hash
tables. Make sure these hpte entries are left untouched.

This patch also adds plpar_pte_read_raw() on the lines of 
plpar_pte_remove_raw().

Thanks
-Sachin





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* On Power machines supporting VRMA, Kexec/Kdump does not work.
* Hypervisor stores VRMA mapping used by the OS, in the hpte hash tables.
* Make sure these hpte entries are left untouched.

Signed-off-by : Sachin Sant <sachinp@in.ibm.com>
Signed-off-by : Mohan Kumar M <mohan@in.ibm.com>
---

diff -Naurp linux-2.6.22-rc2-vrma/arch/powerpc/platforms/pseries/lpar.c linux-2.6.22-rc2-kexec/arch/powerpc/platforms/pseries/lpar.c
--- linux-2.6.22-rc2-vrma/arch/powerpc/platforms/pseries/lpar.c	2007-05-19 09:36:17.000000000 +0530
+++ linux-2.6.22-rc2-kexec/arch/powerpc/platforms/pseries/lpar.c	2007-05-23 13:47:54.000000000 +0530
@@ -369,6 +369,62 @@ static long pSeries_lpar_hpte_remove(uns
 	return -1;
 }
 
+#define VRMA_VPN        ASM_CONST(0x001FFFFFF0000000)
+#define VRMA_MASK       ASM_CONST(0xc000000000000000)
+#define VRMA_HPTE_B_1TB ASM_CONST(0x4000000000000000)
+#define VRMA_NUM        16
+
+unsigned long hpte_vrma_slots[VRMA_NUM];
+unsigned int num_hpte_vrma_slots = 0;
+
+static void pSeries_save_hpte_vrma(void)
+{
+	unsigned int step;
+	unsigned long hash, slot, vaddr;
+	unsigned long dword0, dummy1, rma_size;
+	long lpar_rc;
+	int i;
+	
+	/* Get the RMA size */
+	rma_size = lmb.rmo_size;
+	
+	/* Get the VRMA page size */	
+	step = 1 << ppc64_vrma_page_shift;
+
+	vaddr = VRMA_VPN + rma_size;
+
+	/* Find hpte's with VRMA mappings */
+	for (; vaddr >= VRMA_VPN; vaddr -= step) {
+		hash = hpt_hash(vaddr, ppc64_vrma_page_shift);
+		slot = ((hash & htab_hash_mask) * HPTES_PER_GROUP);	
+
+		for (i = 0; i < HPTES_PER_GROUP; i++) {
+			lpar_rc = plpar_pte_read_raw(0, slot, 
+						&dword0, &dummy1);
+			if (!lpar_rc && dword0 &&
+				((dword0 & VRMA_MASK) == VRMA_HPTE_B_1TB) &&
+				(num_hpte_vrma_slots < VRMA_NUM)) {
+				/* store the hpte */
+				hpte_vrma_slots[num_hpte_vrma_slots++] = slot;
+				break;
+			}
+			slot++;
+		}
+	}
+}
+
+static inline int check_vrma_slot(int slot)
+{
+	int j;
+
+	for (j = 0; j < num_hpte_vrma_slots; j++)
+		if (hpte_vrma_slots[j] == slot) 
+			return 1;
+
+	return 0;
+
+}
+
 static void pSeries_lpar_hptab_clear(void)
 {
 	unsigned long size_bytes = 1UL << ppc64_pft_size;
@@ -376,9 +432,16 @@ static void pSeries_lpar_hptab_clear(voi
 	unsigned long dummy1, dummy2;
 	int i;
 
+	if (have_vrma)
+		pSeries_save_hpte_vrma();
+
 	/* TODO: Use bulk call */
-	for (i = 0; i < hpte_count; i++)
+	for (i = 0; i < hpte_count; i++) {
+		if (have_vrma && check_vrma_slot(i))
+			/* You don't want to remove this hpte */
+			continue;
 		plpar_pte_remove_raw(0, i, 0, &dummy1, &dummy2);
+	}
 }
 
 /*
diff -Naurp linux-2.6.22-rc2-vrma/arch/powerpc/platforms/pseries/plpar_wrappers.h linux-2.6.22-rc2-kexec/arch/powerpc/platforms/pseries/plpar_wrappers.h
--- linux-2.6.22-rc2-vrma/arch/powerpc/platforms/pseries/plpar_wrappers.h	2007-05-19 09:36:17.000000000 +0530
+++ linux-2.6.22-rc2-kexec/arch/powerpc/platforms/pseries/plpar_wrappers.h	2007-05-23 11:38:12.000000000 +0530
@@ -108,6 +108,21 @@ static inline long plpar_pte_read(unsign
 	return rc;
 }
 
+/* plpar_pte_read_raw can be called in real mode. It calls plpar_hcall_raw */
+static inline long plpar_pte_read_raw(unsigned long flags, unsigned long ptex,
+		unsigned long *old_pteh_ret, unsigned long *old_ptel_ret)
+{
+	long rc;
+	unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
+
+	rc = plpar_hcall_raw(H_READ, retbuf, flags, ptex);
+
+	*old_pteh_ret = retbuf[0];
+	*old_ptel_ret = retbuf[1];
+
+	return rc;
+}
+
 static inline long plpar_pte_protect(unsigned long flags, unsigned long ptex,
 		unsigned long avpn)
 {