[PATCH v2 11/12] PCI: hv: Add hypercalls to read/write MMIO space

Michael Kelley
2022-11-11T06:26:26Z

To support PCI pass-thru devices in Confidential VMs, Hyper-V
has added hypercalls to read and write MMIO space. Add the
appropriate definitions to hyperv-tlfs.h and implement
functions to make the hypercalls. These functions are used
in a subsequent patch.

Co-developed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
---
arch/x86/include/asm/hyperv-tlfs.h | 3 ++
drivers/pci/controller/pci-hyperv.c | 64 +++++++++++++++++++++++++++++++++++++
include/asm-generic/hyperv-tlfs.h | 22 +++++++++++++
3 files changed, 89 insertions(+)

diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
index 3089ec3..f769b9d 100644
--- a/arch/x86/include/asm/hyperv-tlfs.h
+++ b/arch/x86/include/asm/hyperv-tlfs.h
@@ -117,6 +117,9 @@
/* Recommend using enlightened VMCS */
#define HV_X64_ENLIGHTENED_VMCS_RECOMMENDED BIT(14)

+/* Use hypercalls for MMIO config space access */
+#define HV_X64_USE_MMIO_HYPERCALLS BIT(21)
+
/*
* CPU management features identification.
* These are HYPERV_CPUID_CPU_MANAGEMENT_FEATURES.EAX bits.
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index ba64284..09b40a1 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -1054,6 +1054,70 @@ static int wslot_to_devfn(u32 wslot)
return PCI_DEVFN(slot_no.bits.dev, slot_no.bits.func);
}

+static void hv_pci_read_mmio(struct device *dev, phys_addr_t gpa, int size, u32 *val)
+{
+ struct hv_mmio_read_input *in;
+ struct hv_mmio_read_output *out;
+ u64 ret;
+
+ /*
+ * Must be called with interrupts disabled so it is safe
+ * to use the per-cpu input argument page. Use it for
+ * both input and output.
+ */
+ in = *this_cpu_ptr(hyperv_pcpu_input_arg);
+ out = *this_cpu_ptr(hyperv_pcpu_input_arg) + sizeof(*in);
+ in->gpa = gpa;
+ in->size = size;
+
+ ret = hv_do_hypercall(HVCALL_MMIO_READ, in, out);
+ if (hv_result_success(ret)) {
+ switch (size) {
+ case 1:
+ *val = *(u8 *)(out->data);
+ break;
+ case 2:
+ *val = *(u16 *)(out->data);
+ break;
+ default:
+ *val = *(u32 *)(out->data);
+ break;
+ }
+ } else
+ dev_err(dev, "MMIO read hypercall error %llx addr %llx size %d\n",
+ ret, gpa, size);
+}
+
+static void hv_pci_write_mmio(struct device *dev, phys_addr_t gpa, int size, u32 val)
+{
+ struct hv_mmio_write_input *in;
+ u64 ret;
+
+ /*
+ * Must be called with interrupts disabled so it is safe
+ * to use the per-cpu input argument memory.
+ */
+ in = *this_cpu_ptr(hyperv_pcpu_input_arg);
+ in->gpa = gpa;
+ in->size = size;
+ switch (size) {
+ case 1:
+ *(u8 *)(in->data) = val;
+ break;
+ case 2:
+ *(u16 *)(in->data) = val;
+ break;
+ default:
+ *(u32 *)(in->data) = val;
+ break;
+ }
+
+ ret = hv_do_hypercall(HVCALL_MMIO_WRITE, in, NULL);
+ if (!hv_result_success(ret))
+ dev_err(dev, "MMIO write hypercall error %llx addr %llx size %d\n",
+ ret, gpa, size);
+}
+
/*
* PCI Configuration Space for these root PCI buses is implemented as a pair
* of pages in memory-mapped I/O space. Writing to the first page chooses
diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
index b17c6ee..fcab07b 100644
--- a/include/asm-generic/hyperv-tlfs.h
+++ b/include/asm-generic/hyperv-tlfs.h
@@ -168,6 +168,8 @@ struct ms_hyperv_tsc_page {
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
#define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
#define HVCALL_MODIFY_SPARSE_GPA_PAGE_HOST_VISIBILITY 0x00db
+#define HVCALL_MMIO_READ 0x0106
+#define HVCALL_MMIO_WRITE 0x0107

/* Extended hypercalls */
#define HV_EXT_CALL_QUERY_CAPABILITIES 0x8001
@@ -790,4 +792,24 @@ struct hv_memory_hint {
union hv_gpa_page_range ranges[];
} __packed;

+/* Data structures for HVCALL_MMIO_READ and HVCALL_MMIO_WRITE */
+#define HV_HYPERCALL_MMIO_MAX_DATA_LENGTH 64
+
+struct hv_mmio_read_input {
+ u64 gpa;
+ u32 size;
+ u32 reserved;
+} __packed;
+
+struct hv_mmio_read_output {
+ u8 data[HV_HYPERCALL_MMIO_MAX_DATA_LENGTH];
+} __packed;
+
+struct hv_mmio_write_input {
+ u64 gpa;
+ u32 size;
+ u32 reserved;
+ u8 data[HV_HYPERCALL_MMIO_MAX_DATA_LENGTH];
+} __packed;
+
#endif
--
1.8.3.1