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From:   Jeffrey Hugo <quic_jhugo@quicinc.com>
To:     <kys@microsoft.com>, <haiyangz@microsoft.com>,
        <sthemmin@microsoft.com>, <wei.liu@kernel.org>,
        <decui@microsoft.com>, <lorenzo.pieralisi@arm.com>,
        <robh@kernel.org>, <kw@linux.com>, <bhelgaas@google.com>
CC:     <bjorn.andersson@linaro.org>, <linux-hyperv@vger.kernel.org>,
        <linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        Jeffrey Hugo <quic_jhugo@quicinc.com>
Subject: [PATCH] PCI: hv: Fix hv_arch_irq_unmask() for multi-MSI
Date:   Wed, 27 Apr 2022 08:07:33 -0600
Message-ID: <1651068453-29588-1-git-send-email-quic_jhugo@quicinc.com>
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Precedence: bulk

In the multi-MSI case, hv_arch_irq_unmask() will only operate on the first
MSI of the N allocated.  This is because only the first msi_desc is cached
and it is shared by all the MSIs of the multi-MSI block.  This means that
hv_arch_irq_unmask() gets the correct address, but the wrong data (always
0).

This can break MSIs.

Lets assume MSI0 is vector 34 on CPU0, and MSI1 is vector 33 on CPU0.

hv_arch_irq_unmask() is called on MSI0.  It uses a hypercall to configure
the MSI address and data (0) to vector 34 of CPU0.  This is correct.  Then
hv_arch_irq_unmask is called on MSI1.  It uses another hypercall to
configure the MSI address and data (0) to vector 33 of CPU0.  This is
wrong, and results in both MSI0 and MSI1 being routed to vector 33.  Linux
will observe extra instances of MSI1 and no instances of MSI0 despite the
endpoint device behaving correctly.

For the multi-MSI case, we need unique address and data info for each MSI,
but the cached msi_desc does not provide that.  However, that information
can be gotten from the int_desc cached in the chip_data by
compose_msi_msg().  Fix the multi-MSI case to use that cached information
instead.  Since hv_set_msi_entry_from_desc() is no longer applicable,
remove it.

Signed-off-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
---
 drivers/pci/controller/pci-hyperv.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 5800ecf..7aea0b7 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -611,13 +611,6 @@ static unsigned int hv_msi_get_int_vector(struct irq_data *data)
 	return cfg->vector;
 }
 
-static void hv_set_msi_entry_from_desc(union hv_msi_entry *msi_entry,
-				       struct msi_desc *msi_desc)
-{
-	msi_entry->address.as_uint32 = msi_desc->msg.address_lo;
-	msi_entry->data.as_uint32 = msi_desc->msg.data;
-}
-
 static int hv_msi_prepare(struct irq_domain *domain, struct device *dev,
 			  int nvec, msi_alloc_info_t *info)
 {
@@ -647,6 +640,7 @@ static void hv_arch_irq_unmask(struct irq_data *data)
 {
 	struct msi_desc *msi_desc = irq_data_get_msi_desc(data);
 	struct hv_retarget_device_interrupt *params;
+	struct tran_int_desc *int_desc;
 	struct hv_pcibus_device *hbus;
 	struct cpumask *dest;
 	cpumask_var_t tmp;
@@ -661,6 +655,7 @@ static void hv_arch_irq_unmask(struct irq_data *data)
 	pdev = msi_desc_to_pci_dev(msi_desc);
 	pbus = pdev->bus;
 	hbus = container_of(pbus->sysdata, struct hv_pcibus_device, sysdata);
+	int_desc = data->chip_data;
 
 	spin_lock_irqsave(&hbus->retarget_msi_interrupt_lock, flags);
 
@@ -668,7 +663,8 @@ static void hv_arch_irq_unmask(struct irq_data *data)
 	memset(params, 0, sizeof(*params));
 	params->partition_id = HV_PARTITION_ID_SELF;
 	params->int_entry.source = HV_INTERRUPT_SOURCE_MSI;
-	hv_set_msi_entry_from_desc(&params->int_entry.msi_entry, msi_desc);
+	params->int_entry.msi_entry.address.as_uint32 = int_desc->address & 0xffffffff;
+	params->int_entry.msi_entry.data.as_uint32 = int_desc->data;
 	params->device_id = (hbus->hdev->dev_instance.b[5] << 24) |
 			   (hbus->hdev->dev_instance.b[4] << 16) |
 			   (hbus->hdev->dev_instance.b[7] << 8) |
-- 
2.7.4