[PATCH v2] hw/block/nvme: map prp fix if prp2 contains non-zero offset

[Padmakar Kalghatgi]

From: padmakar <p.kalghatgi@samsung.com>

nvme_map_prp needs to calculate the number of list entries based on the
offset value. For the subsequent PRP2 list, need to ensure the number of
entries is within the MAX number of PRP entries for a page.

Signed-off-by: Padmakar Kalghatgi <p.kalghatgi@samsung.com>
---
 -v2:
     removed extraneous spacing in the comments(Keith) 
         used bitwise operator instead of the modulo operator(Keith)
         
 hw/block/nvme.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index d439e44..a4c4f9d 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -577,7 +577,12 @@ static uint16_t nvme_map_prp(NvmeCtrl *n, NvmeSg *sg, 
uint64_t prp1,
             uint32_t nents, prp_trans;
             int i = 0;
 
-            nents = (len + n->page_size - 1) >> n->page_bits;
+            /*
+             * The first PRP list entry, pointed by PRP2 can contain
+             * offsets. Hence, we need calculate the no of entries in
+             * prp2 based on the offset it has.
+             */
+            nents = (n->page_size - (prp2 & (n->page_size - 1))) >> 3;
             prp_trans = MIN(n->max_prp_ents, nents) * sizeof(uint64_t);
             ret = nvme_addr_read(n, prp2, (void *)prp_list, prp_trans);
             if (ret) {
@@ -588,7 +593,7 @@ static uint16_t nvme_map_prp(NvmeCtrl *n, NvmeSg *sg, 
uint64_t prp1,
             while (len != 0) {
                 uint64_t prp_ent = le64_to_cpu(prp_list[i]);
 
-                if (i == n->max_prp_ents - 1 && len > n->page_size) {
+                if (i == nents - 1 && len > n->page_size) {
                     if (unlikely(prp_ent & (n->page_size - 1))) {
                         trace_pci_nvme_err_invalid_prplist_ent(prp_ent);
                         status = NVME_INVALID_PRP_OFFSET | NVME_DNR;
@@ -597,7 +602,8 @@ static uint16_t nvme_map_prp(NvmeCtrl *n, NvmeSg *sg, 
uint64_t prp1,
 
                     i = 0;
                     nents = (len + n->page_size - 1) >> n->page_bits;
-                    prp_trans = MIN(n->max_prp_ents, nents) * sizeof(uint64_t);
+                    nents = MIN(nents, n->max_prp_ents);
+                    prp_trans = nents * sizeof(uint64_t);
                     ret = nvme_addr_read(n, prp_ent, (void *)prp_list,
                                          prp_trans);
                     if (ret) {
-- 
2.7.0.windows.1