[Patch ] Kexec Kdump support for POWER6

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

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Paul, here is the final version of the patch with all review
comments incorporated. 

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

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

diff -Naurp a/arch/powerpc/platforms/pseries/lpar.c b/arch/powerpc/platforms/pseries/lpar.c
--- a/arch/powerpc/platforms/pseries/lpar.c	2007-05-19 09:36:17.000000000 +0530
+++ b/arch/powerpc/platforms/pseries/lpar.c	2007-05-29 10:45:34.000000000 +0530
@@ -373,12 +373,23 @@ static void pSeries_lpar_hptab_clear(voi
 {
 	unsigned long size_bytes = 1UL << ppc64_pft_size;
 	unsigned long hpte_count = size_bytes >> 4;
-	unsigned long dummy1, dummy2;
+	unsigned long dummy1, dummy2, dword0;
+	long lpar_rc;
 	int i;
 
 	/* TODO: Use bulk call */
-	for (i = 0; i < hpte_count; i++)
-		plpar_pte_remove_raw(0, i, 0, &dummy1, &dummy2);
+	for (i = 0; i < hpte_count; i++) {
+		/* dont remove HPTEs with VRMA mappings */
+		lpar_rc = plpar_pte_remove_raw(H_ANDCOND, i, HPTE_V_1TB_SEG,
+						&dummy1, &dummy2);
+		if (lpar_rc == H_NOT_FOUND) {
+			lpar_rc = plpar_pte_read_raw(0, i, &dword0, &dummy1);
+			if (!lpar_rc && ((dword0 & HPTE_V_VRMA_MASK)
+				!= HPTE_V_VRMA_MASK))
+				/* Can be hpte for 1TB Seg. So remove it */
+				plpar_pte_remove_raw(0, i, 0, &dummy1, &dummy2);
+		}
+	}
 }
 
 /*
diff -Naurp a/arch/powerpc/platforms/pseries/plpar_wrappers.h b/arch/powerpc/platforms/pseries/plpar_wrappers.h
--- a/arch/powerpc/platforms/pseries/plpar_wrappers.h	2007-05-19 09:36:17.000000000 +0530
+++ b/arch/powerpc/platforms/pseries/plpar_wrappers.h	2007-05-25 12:20:38.000000000 +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)
 {
diff -Naurp a/include/asm-powerpc/mmu-hash64.h b/include/asm-powerpc/mmu-hash64.h
--- a/include/asm-powerpc/mmu-hash64.h	2007-05-19 09:36:17.000000000 +0530
+++ b/include/asm-powerpc/mmu-hash64.h	2007-05-29 10:46:22.000000000 +0530
@@ -94,6 +94,9 @@ extern char initial_stab[];
 #define HPTE_R_C		ASM_CONST(0x0000000000000080)
 #define HPTE_R_R		ASM_CONST(0x0000000000000100)
 
+#define HPTE_V_1TB_SEG          ASM_CONST(0x4000000000000000)
+#define HPTE_V_VRMA_MASK        ASM_CONST(0x4001ffffff000000)
+
 /* Values for PP (assumes Ks=0, Kp=1) */
 /* pp0 will always be 0 for linux     */
 #define PP_RWXX	0	/* Supervisor read/write, User none */