linux-kernel - [PATCH v2 3/4] PCI: hv: Change pci_protocol

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Message-Id: <1574234218-49195-4-git-send-email-decui@microsoft.com>
Date:   Tue, 19 Nov 2019 23:16:57 -0800
From:   Dexuan Cui <decui@...rosoft.com>
To:     kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org, lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        linux-hyperv@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com,
        Alexander.Levin@...rosoft.com
Cc:     Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v2 3/4] PCI: hv: Change pci_protocol_version to per-hbus

A VM can have multiple Hyper-V hbus. It's incorrect to set the global
variable 'pci_protocol_version' when *every* hbus is initialized in
hv_pci_protocol_negotiation(). This is not an issue in practice since
every hbus should have the same value of hbus->protocol_version, but
we should make the variable per-hbus, so in case we have busses
with different protocol_versions, the driver can still work correctly.

Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---

changes in v2: Improved the changelog by making it clear that this patch
fixes a potential bug if we have busses with different protocol_versions.

 drivers/pci/controller/pci-hyperv.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index e71eb6e0bfdd..d7e05d436b5e 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -76,11 +76,6 @@ static enum pci_protocol_version_t pci_protocol_versions[] = {
 	PCI_PROTOCOL_VERSION_1_1,
 };
 
-/*
- * Protocol version negotiated by hv_pci_protocol_negotiation().
- */
-static enum pci_protocol_version_t pci_protocol_version;
-
 #define PCI_CONFIG_MMIO_LENGTH	0x2000
 #define CFG_PAGE_OFFSET 0x1000
 #define CFG_PAGE_SIZE (PCI_CONFIG_MMIO_LENGTH - CFG_PAGE_OFFSET)
@@ -462,6 +457,8 @@ enum hv_pcibus_state {
 
 struct hv_pcibus_device {
 	struct pci_sysdata sysdata;
+	/* Protocol version negotiated with the host */
+	enum pci_protocol_version_t protocol_version;
 	enum hv_pcibus_state state;
 	refcount_t remove_lock;
 	struct hv_device *hdev;
@@ -1225,7 +1222,7 @@ static void hv_irq_unmask(struct irq_data *data)
 	 * negative effect (yet?).
 	 */
 
-	if (pci_protocol_version >= PCI_PROTOCOL_VERSION_1_2) {
+	if (hbus->protocol_version >= PCI_PROTOCOL_VERSION_1_2) {
 		/*
 		 * PCI_PROTOCOL_VERSION_1_2 supports the VP_SET version of the
 		 * HVCALL_RETARGET_INTERRUPT hypercall, which also coincides
@@ -1395,7 +1392,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 	ctxt.pci_pkt.completion_func = hv_pci_compose_compl;
 	ctxt.pci_pkt.compl_ctxt = &comp;
 
-	switch (pci_protocol_version) {
+	switch (hbus->protocol_version) {
 	case PCI_PROTOCOL_VERSION_1_1:
 		size = hv_compose_msi_req_v1(&ctxt.int_pkts.v1,
 					dest,
@@ -2415,6 +2412,7 @@ static int hv_pci_protocol_negotiation(struct hv_device *hdev,
 				       enum pci_protocol_version_t version[],
 				       int num_version)
 {
+	struct hv_pcibus_device *hbus = hv_get_drvdata(hdev);
 	struct pci_version_request *version_req;
 	struct hv_pci_compl comp_pkt;
 	struct pci_packet *pkt;
@@ -2454,10 +2452,10 @@ static int hv_pci_protocol_negotiation(struct hv_device *hdev,
 		}
 
 		if (comp_pkt.completion_status >= 0) {
-			pci_protocol_version = version[i];
+			hbus->protocol_version = version[i];
 			dev_info(&hdev->device,
 				"PCI VMBus probing: Using version %#x\n",
-				pci_protocol_version);
+				hbus->protocol_version);
 			goto exit;
 		}
 
@@ -2741,7 +2739,7 @@ static int hv_send_resources_allocated(struct hv_device *hdev)
 	u32 wslot;
 	int ret;
 
-	size_res = (pci_protocol_version < PCI_PROTOCOL_VERSION_1_2)
+	size_res = (hbus->protocol_version < PCI_PROTOCOL_VERSION_1_2)
 			? sizeof(*res_assigned) : sizeof(*res_assigned2);
 
 	pkt = kmalloc(sizeof(*pkt) + size_res, GFP_KERNEL);
@@ -2760,7 +2758,7 @@ static int hv_send_resources_allocated(struct hv_device *hdev)
 		pkt->completion_func = hv_pci_generic_compl;
 		pkt->compl_ctxt = &comp_pkt;
 
-		if (pci_protocol_version < PCI_PROTOCOL_VERSION_1_2) {
+		if (hbus->protocol_version < PCI_PROTOCOL_VERSION_1_2) {
 			res_assigned =
 				(struct pci_resources_assigned *)&pkt->message;
 			res_assigned->message_type.type =
@@ -3182,7 +3180,7 @@ static int hv_pci_resume(struct hv_device *hdev)
 		return ret;
 
 	/* Only use the version that was in use before hibernation. */
-	version[0] = pci_protocol_version;
+	version[0] = hbus->protocol_version;
 	ret = hv_pci_protocol_negotiation(hdev, version, 1);
 	if (ret)
 		goto out;
-- 
2.19.1