git: f64329bcdc4f - main - Extract the logic from pmap_kextract

[Andrew Turner]

The branch main has been updated by andrew:

URL: https://cgit.FreeBSD.org/src/commit/?id=f64329bcdc4f7cf41c03bfbcf7e6a7525dad68fd

commit f64329bcdc4f7cf41c03bfbcf7e6a7525dad68fd
Author:     Andrew Turner <andrew at FreeBSD.org>
AuthorDate: 2021-01-15 18:48:43 +0000
Commit:     Andrew Turner <andrew at FreeBSD.org>
CommitDate: 2021-01-15 19:08:01 +0000

    Extract the logic from pmap_kextract
    
    This allows us to use it when we only need to check if the virtual address
    is valid. For example when checking if an address in the DMAP region is
    mapped.
    
    Reviewed by:    kib, markj
    Sponsored by:   Innovate UK
    Differential Revision:  https://reviews.freebsd.org/D27621
---
 sys/arm64/arm64/pmap.c     | 73 +++++++++++++++++++++++++++++++++++++---------
 sys/arm64/include/armreg.h |  1 +
 sys/arm64/include/pmap.h   |  1 +
 3 files changed, 62 insertions(+), 13 deletions(-)

diff --git a/sys/arm64/arm64/pmap.c b/sys/arm64/arm64/pmap.c
index 86ab5cb43ae9..d4047fc84096 100644
--- a/sys/arm64/arm64/pmap.c
+++ b/sys/arm64/arm64/pmap.c
@@ -1365,16 +1365,42 @@ pmap_extract_and_hold(pmap_t pmap, vm_offset_t va, vm_prot_t prot)
 	return (m);
 }
 
-vm_paddr_t
-pmap_kextract(vm_offset_t va)
+/*
+ * Walks the page tables to translate a kernel virtual address to a
+ * physical address. Returns true if the kva is valid and stores the
+ * physical address in pa if it is not NULL.
+ */
+bool
+pmap_klookup(vm_offset_t va, vm_paddr_t *pa)
 {
 	pt_entry_t *pte, tpte;
+	register_t intr;
+	uint64_t par;
+
+	/*
+	 * Disable interrupts so we don't get interrupted between asking
+	 * for address translation, and getting the result back.
+	 */
+	intr = intr_disable();
+	par = arm64_address_translate_s1e1r(va);
+	intr_restore(intr);
+
+	if (PAR_SUCCESS(par)) {
+		if (pa != NULL)
+			*pa = (par & PAR_PA_MASK) | (va & PAR_LOW_MASK);
+		return (true);
+	}
+
+	/*
+	 * Fall back to walking the page table. The address translation
+	 * instruction may fail when the page is in a break-before-make
+	 * sequence. As we only clear the valid bit in said sequence we
+	 * can walk the page table to find the physical address.
+	 */
 
-	if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS)
-		return (DMAP_TO_PHYS(va));
 	pte = pmap_l1(kernel_pmap, va);
 	if (pte == NULL)
-		return (0);
+		return (false);
 
 	/*
 	 * A concurrent pmap_update_entry() will clear the entry's valid bit
@@ -1384,20 +1410,41 @@ pmap_kextract(vm_offset_t va)
 	 */
 	tpte = pmap_load(pte);
 	if (tpte == 0)
-		return (0);
-	if ((tpte & ATTR_DESCR_TYPE_MASK) == ATTR_DESCR_TYPE_BLOCK)
-		return ((tpte & ~ATTR_MASK) | (va & L1_OFFSET));
+		return (false);
+	if ((tpte & ATTR_DESCR_TYPE_MASK) == ATTR_DESCR_TYPE_BLOCK) {
+		if (pa != NULL)
+			*pa = (tpte & ~ATTR_MASK) | (va & L1_OFFSET);
+		return (true);
+	}
 	pte = pmap_l1_to_l2(&tpte, va);
 	tpte = pmap_load(pte);
 	if (tpte == 0)
-		return (0);
-	if ((tpte & ATTR_DESCR_TYPE_MASK) == ATTR_DESCR_TYPE_BLOCK)
-		return ((tpte & ~ATTR_MASK) | (va & L2_OFFSET));
+		return (false);
+	if ((tpte & ATTR_DESCR_TYPE_MASK) == ATTR_DESCR_TYPE_BLOCK) {
+		if (pa != NULL)
+			*pa = (tpte & ~ATTR_MASK) | (va & L2_OFFSET);
+		return (true);
+	}
 	pte = pmap_l2_to_l3(&tpte, va);
 	tpte = pmap_load(pte);
 	if (tpte == 0)
+		return (false);
+	if (pa != NULL)
+		*pa = (tpte & ~ATTR_MASK) | (va & L3_OFFSET);
+	return (true);
+}
+
+vm_paddr_t
+pmap_kextract(vm_offset_t va)
+{
+	vm_paddr_t pa;
+
+	if (va >= DMAP_MIN_ADDRESS && va < DMAP_MAX_ADDRESS)
+		return (DMAP_TO_PHYS(va));
+
+	if (pmap_klookup(va, &pa) == false)
 		return (0);
-	return ((tpte & ~ATTR_MASK) | (va & L3_OFFSET));
+	return (pa);
 }
 
 /***************************************************
@@ -6833,7 +6880,7 @@ pmap_fault(pmap_t pmap, uint64_t esr, uint64_t far)
 			 * critical section.  Therefore, we must check the
 			 * address without acquiring the kernel pmap's lock.
 			 */
-			if (pmap_kextract(far) != 0)
+			if (pmap_klookup(far, NULL))
 				rv = KERN_SUCCESS;
 		} else {
 			PMAP_LOCK(pmap);
diff --git a/sys/arm64/include/armreg.h b/sys/arm64/include/armreg.h
index 35a8f6dd488b..201d7559320b 100644
--- a/sys/arm64/include/armreg.h
+++ b/sys/arm64/include/armreg.h
@@ -743,6 +743,7 @@
 #define	PAR_F			(0x1 << PAR_F_SHIFT)
 #define	PAR_SUCCESS(x)		(((x) & PAR_F) == 0)
 /* When PAR_F == 0 (success) */
+#define	PAR_LOW_MASK		0xfff
 #define	PAR_SH_SHIFT		7
 #define	PAR_SH_MASK		(0x3 << PAR_SH_SHIFT)
 #define	PAR_NS_SHIFT		9
diff --git a/sys/arm64/include/pmap.h b/sys/arm64/include/pmap.h
index 059d188ff847..b05fee999c73 100644
--- a/sys/arm64/include/pmap.h
+++ b/sys/arm64/include/pmap.h
@@ -167,6 +167,7 @@ void	pmap_bootstrap(vm_offset_t, vm_offset_t, vm_paddr_t, vm_size_t);
 int	pmap_change_attr(vm_offset_t va, vm_size_t size, int mode);
 void	pmap_kenter(vm_offset_t sva, vm_size_t size, vm_paddr_t pa, int mode);
 void	pmap_kenter_device(vm_offset_t, vm_size_t, vm_paddr_t);
+bool	pmap_klookup(vm_offset_t va, vm_paddr_t *pa);
 vm_paddr_t pmap_kextract(vm_offset_t va);
 void	pmap_kremove(vm_offset_t);
 void	pmap_kremove_device(vm_offset_t, vm_size_t);