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

[Klaus Jensen]

On Apr  8 21:53, Padmakar Kalghatgi wrote:

From: padmakar 

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 
---
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..efb7368 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)) >> 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




LGTM.

Reviewed-by: Klaus Jensen 


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

[Keith Busch]

On Thu, Apr 08, 2021 at 09:53:13PM +0530, Padmakar Kalghatgi wrote:
> +/*
> + *   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.
> + */

This comment has some unnecessary spacing at the beginning.

> +nents = (n->page_size - (prp2 % n->page_size)) >> 3;

page_size is a always a power of two, so let's replace the costly modulo
with:

nents = (n->page_size - (prp2 & (n->page_size - 1))) >> 3;

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

[Klaus Jensen]

On Apr  9 06:38, Keith Busch wrote:

On Thu, Apr 08, 2021 at 09:53:13PM +0530, Padmakar Kalghatgi wrote:

+/*
+ *   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.
+ */


This comment has some unnecessary spacing at the beginning.


+nents = (n->page_size - (prp2 % n->page_size)) >> 3;


page_size is a always a power of two, so let's replace the costly modulo
with:

nents = (n->page_size - (prp2 & (n->page_size - 1))) >> 3;



Good point.

I'll fix both issues and queue the patch.


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