From: Jeffrey Hugo quic_jhugo@quicinc.com
commit b4b77778ecc5bfbd4e77de1b2fd5c1dd3c655f1f upstream.
Currently if compose_msi_msg() is called multiple times, it will free any previous IRTE allocation, and generate a new allocation. While nothing prevents this from occurring, it is extraneous when Linux could just reuse the existing allocation and avoid a bunch of overhead.
However, when future IRTE allocations operate on blocks of MSIs instead of a single line, freeing the allocation will impact all of the lines. This could cause an issue where an allocation of N MSIs occurs, then some of the lines are retargeted, and finally the allocation is freed/reallocated. The freeing of the allocation removes all of the configuration for the entire block, which requires all the lines to be retargeted, which might not happen since some lines might already be unmasked/active.
Signed-off-by: Jeffrey Hugo quic_jhugo@quicinc.com Reviewed-by: Dexuan Cui decui@microsoft.com Tested-by: Dexuan Cui decui@microsoft.com Tested-by: Michael Kelley mikelley@microsoft.com Link: https://lore.kernel.org/r/1652282582-21595-1-git-send-email-quic_jhugo@quici... Signed-off-by: Wei Liu wei.liu@kernel.org Signed-off-by: Carl Vanderlip quic_carlv@quicinc.com --- drivers/pci/controller/pci-hyperv.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c index 560a9aa297c3..0200a291413a 100644 --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -1458,6 +1458,15 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg) u32 size; int ret;
+ /* Reuse the previous allocation */ + if (data->chip_data) { + int_desc = data->chip_data; + msg->address_hi = int_desc->address >> 32; + msg->address_lo = int_desc->address & 0xffffffff; + msg->data = int_desc->data; + return; + } + pdev = msi_desc_to_pci_dev(irq_data_get_msi_desc(data)); dest = irq_data_get_effective_affinity_mask(data); pbus = pdev->bus; @@ -1467,13 +1476,6 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg) if (!hpdev) goto return_null_message;
- /* Free any previous message that might have already been composed. */ - if (data->chip_data) { - int_desc = data->chip_data; - data->chip_data = NULL; - hv_int_desc_free(hpdev, int_desc); - } - int_desc = kzalloc(sizeof(*int_desc), GFP_ATOMIC); if (!int_desc) goto drop_reference;