* [PATCH v1 1/1] vfio/nvgrace-gpu: carve out non cached reserved region from device memory
@ 2023-11-15 8:07 ankita
2023-11-27 21:28 ` Alex Williamson
0 siblings, 1 reply; 2+ messages in thread
From: ankita @ 2023-11-15 8:07 UTC (permalink / raw)
To: ankita, jgg, alex.williamson, yishaih, shameerali.kolothum.thodi,
kevin.tian
Cc: aniketa, cjia, kwankhede, targupta, vsethi, acurrid, apopple,
jhubbard, danw, anuaggarwal, kvm, linux-kernel
From: Ankit Agrawal <ankita@nvidia.com>
The NVIDIA's upcoming Grace Hopper Superchip GPU device driver has a
requirement of a reserved 1G uncached RAM-like region to support the
Multi-Instance GPU (MIG) feature [1]. Carve out the region from the device
memory.
Based on [2], the requisite properties (uncached, unaligned access) can be
achieved through a VM mapping (S1) of NORMAL_NC and host (S2) mapping
with MemAttr[2:0]=0b101. Currently there is no provision in KVM for a S2
mapping with MemAttr[2:0]=0b101, but there is an ongoing effort to provide
the same [3].
This patch change goes on top of the VFIO PCI variant driver proposed for
the Grace Hopper devices in [4], which facilitates the entire device memory
to be mapped as NORMAL in S2. To provide a different non-cached property to
the reserved 1G region, it needs to be carved out from the device memory and
mapped as a separate region in Qemu VMA with pgprot_writecombine().
pgprot_writecombine() sets the Qemu VMA page properties (pgprot) as
NORMAL_NC. Using the proposed changes in [5] and [3], KVM marks the region
with MemAttr[2:0]=0b101 in S2.
The new region (represented as resmem in the patch) is carved out from
the tail end of the device memory host physical address range and exposed
as a 64b BAR (comprising of region 2 and 3) to the VM.
The remaining device memory (termed as usable memory and represented
using usemem) continues to be NORMAL cacheable and is exposed as 64b BAR
with region 4 and 5. This memory is added by the VM Nvidia device driver [6]
to the VM kernel as memblocks. Hence make the usable memory size memblock
aligned.
The memory layout on the host looks like the following:
devmem (memlength)
|--------------------------------------------------|
|-------------cached------------------------|--NC--|
| |
usemem.phys/memphys resmem.phys
[1] https://www.nvidia.com/en-in/technologies/multi-instance-gpu/
[2] section D8.5.5 of DDI0487_I_a_a-profile_architecture_reference_manual.pdf
[3] https://lore.kernel.org/all/20230907181459.18145-3-ankita@nvidia.com/
[4] https://lore.kernel.org/all/20231114081611.30550-1-ankita@nvidia.com/
[5] https://lore.kernel.org/all/20230907181459.18145-2-ankita@nvidia.com/
[6] https://github.com/NVIDIA/open-gpu-kernel-modules
Signed-off-by: Ankit Agrawal <ankita@nvidia.com>
---
drivers/vfio/pci/nvgrace-gpu/main.c | 236 +++++++++++++++++++++-------
1 file changed, 178 insertions(+), 58 deletions(-)
diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c
index a3dbee6b87de..87afbda39939 100644
--- a/drivers/vfio/pci/nvgrace-gpu/main.c
+++ b/drivers/vfio/pci/nvgrace-gpu/main.c
@@ -7,24 +7,62 @@
#include <linux/vfio_pci_core.h>
#include <linux/vfio.h>
+/* Memory size expected as non cached and reserved by the VM driver */
+#define RESMEM_SIZE 0x40000000
+#define MEMBLK_SIZE 0x20000000
+
+struct mem_region {
+ phys_addr_t memphys; /* Base address of the region */
+ size_t memlength; /* Region size */
+ u32 bar_regs[2]; /* Emulated BAR offset registers */
+ void *memmap; /* Memremap pointer to the region */
+};
+
struct nvgrace_gpu_vfio_pci_core_device {
struct vfio_pci_core_device core_device;
- phys_addr_t memphys;
- size_t memlength;
- u32 bar_regs[2];
- void *memmap;
+ /* Cached and usable memory for the VM. */
+ struct mem_region usemem;
+ /* Non cached memory carved out from the end of device memory */
+ struct mem_region resmem;
struct mutex memmap_lock;
};
+/* Choose the structure corresponding to the BAR under question. */
+static int nvgrace_gpu_vfio_pci_get_mem_region(int index,
+ struct nvgrace_gpu_vfio_pci_core_device *nvdev,
+ struct mem_region *region)
+{
+ if (index == VFIO_PCI_BAR4_REGION_INDEX)
+ *region = nvdev->usemem;
+ else if (index == VFIO_PCI_BAR2_REGION_INDEX)
+ *region = nvdev->resmem;
+ else
+ return -EINVAL;
+
+ return 0;
+}
+
+static bool nvgrace_gpu_vfio_pci_is_fake_bar(int index)
+{
+ if (index == VFIO_PCI_BAR2_REGION_INDEX ||
+ index == VFIO_PCI_BAR4_REGION_INDEX)
+ return true;
+
+ return false;
+}
+
static void init_fake_bar_emu_regs(struct vfio_device *core_vdev)
{
struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
core_vdev, struct nvgrace_gpu_vfio_pci_core_device,
core_device.vdev);
- nvdev->bar_regs[0] = PCI_BASE_ADDRESS_MEM_TYPE_64 |
- PCI_BASE_ADDRESS_MEM_PREFETCH;
- nvdev->bar_regs[1] = 0;
+ nvdev->resmem.bar_regs[0] = PCI_BASE_ADDRESS_MEM_TYPE_64 |
+ PCI_BASE_ADDRESS_MEM_PREFETCH;
+ nvdev->resmem.bar_regs[1] = 0;
+ nvdev->usemem.bar_regs[0] = PCI_BASE_ADDRESS_MEM_TYPE_64 |
+ PCI_BASE_ADDRESS_MEM_PREFETCH;
+ nvdev->usemem.bar_regs[1] = 0;
}
static bool is_fake_bar_pcicfg_emu_reg_access(loff_t pos)
@@ -33,7 +71,7 @@ static bool is_fake_bar_pcicfg_emu_reg_access(loff_t pos)
u64 offset = pos & VFIO_PCI_OFFSET_MASK;
if ((index == VFIO_PCI_CONFIG_REGION_INDEX) &&
- (offset == PCI_BASE_ADDRESS_2 || offset == PCI_BASE_ADDRESS_3))
+ (offset >= PCI_BASE_ADDRESS_2 && offset <= PCI_BASE_ADDRESS_5))
return true;
return false;
@@ -67,9 +105,9 @@ static void nvgrace_gpu_vfio_pci_close_device(struct vfio_device *core_vdev)
core_vdev, struct nvgrace_gpu_vfio_pci_core_device,
core_device.vdev);
- if (nvdev->memmap) {
- memunmap(nvdev->memmap);
- nvdev->memmap = NULL;
+ if (nvdev->usemem.memmap) {
+ memunmap(nvdev->usemem.memmap);
+ nvdev->usemem.memmap = NULL;
}
mutex_destroy(&nvdev->memmap_lock);
@@ -78,7 +116,7 @@ static void nvgrace_gpu_vfio_pci_close_device(struct vfio_device *core_vdev)
}
static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
- struct vm_area_struct *vma)
+ struct vm_area_struct *vma)
{
struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev);
@@ -87,11 +125,17 @@ static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
unsigned int index;
u64 req_len, pgoff, end;
int ret = 0;
+ struct mem_region memregion;
index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
- if (index != VFIO_PCI_BAR2_REGION_INDEX)
+
+ if (!nvgrace_gpu_vfio_pci_is_fake_bar(index))
return vfio_pci_core_mmap(core_vdev, vma);
+ ret = nvgrace_gpu_vfio_pci_get_mem_region(index, nvdev, &memregion);
+ if (ret)
+ return ret;
+
/*
* Request to mmap the BAR. Map to the CPU accessible memory on the
* GPU using the memory information gathered from the system ACPI
@@ -101,7 +145,7 @@ static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
if (check_sub_overflow(vma->vm_end, vma->vm_start, &req_len) ||
- check_add_overflow(PHYS_PFN(nvdev->memphys), pgoff, &start_pfn) ||
+ check_add_overflow(PHYS_PFN(memregion.memphys), pgoff, &start_pfn) ||
check_add_overflow(PFN_PHYS(pgoff), req_len, &end))
return -EOVERFLOW;
@@ -109,9 +153,16 @@ static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
* Check that the mapping request does not go beyond available device
* memory size
*/
- if (end > nvdev->memlength)
+ if (end > memregion.memlength)
return -EINVAL;
+ /*
+ * The carved out region of the device memory needs the NORMAL_NC
+ * property. Communicate as such to the hypervisor.
+ */
+ if (index == VFIO_PCI_BAR2_REGION_INDEX)
+ vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+
/*
* Perform a PFN map to the memory and back the device BAR by the
* GPU memory.
@@ -142,7 +193,12 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
unsigned long minsz = offsetofend(struct vfio_region_info, offset);
struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev);
+ struct vfio_region_info_cap_sparse_mmap *sparse;
+ struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
struct vfio_region_info info;
+ struct mem_region memregion;
+ uint32_t size;
+ int ret;
if (copy_from_user(&info, (void __user *)arg, minsz))
return -EFAULT;
@@ -150,16 +206,14 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
if (info.argsz < minsz)
return -EINVAL;
- if (info.index == VFIO_PCI_BAR2_REGION_INDEX) {
+ if (nvgrace_gpu_vfio_pci_is_fake_bar(info.index)) {
+ ret = nvgrace_gpu_vfio_pci_get_mem_region(info.index, nvdev, &memregion);
+ if (ret)
+ return ret;
/*
* Request to determine the BAR region information. Send the
* GPU memory information.
*/
- uint32_t size;
- int ret;
- struct vfio_region_info_cap_sparse_mmap *sparse;
- struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
-
size = struct_size(sparse, areas, 1);
/*
@@ -173,7 +227,7 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
sparse->nr_areas = 1;
sparse->areas[0].offset = 0;
- sparse->areas[0].size = nvdev->memlength;
+ sparse->areas[0].size = memregion.memlength;
sparse->header.id = VFIO_REGION_INFO_CAP_SPARSE_MMAP;
sparse->header.version = 1;
@@ -188,7 +242,7 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
* Given that the memory is exposed as a BAR and may not be
* aligned, roundup to the next power-of-2.
*/
- info.size = roundup_pow_of_two(nvdev->memlength);
+ info.size = roundup_pow_of_two(memregion.memlength);
info.flags = VFIO_REGION_INFO_FLAG_READ |
VFIO_REGION_INFO_FLAG_WRITE |
VFIO_REGION_INFO_FLAG_MMAP;
@@ -201,8 +255,8 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
} else {
vfio_info_cap_shift(&caps, sizeof(info));
if (copy_to_user((void __user *)arg +
- sizeof(info), caps.buf,
- caps.size)) {
+ sizeof(info), caps.buf,
+ caps.size)) {
kfree(caps.buf);
return -EFAULT;
}
@@ -211,7 +265,7 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
kfree(caps.buf);
}
return copy_to_user((void __user *)arg, &info, minsz) ?
- -EFAULT : 0;
+ -EFAULT : 0;
}
return vfio_pci_core_ioctl(core_vdev, VFIO_DEVICE_GET_REGION_INFO, arg);
}
@@ -228,12 +282,13 @@ static long nvgrace_gpu_vfio_pci_ioctl(struct vfio_device *core_vdev,
return vfio_pci_core_ioctl(core_vdev, cmd, arg);
}
-static int nvgrace_gpu_memmap(struct nvgrace_gpu_vfio_pci_core_device *nvdev)
+static int nvgrace_gpu_memmap(struct nvgrace_gpu_vfio_pci_core_device *nvdev,
+ struct mem_region *memregion)
{
mutex_lock(&nvdev->memmap_lock);
- if (!nvdev->memmap) {
- nvdev->memmap = memremap(nvdev->memphys, nvdev->memlength, MEMREMAP_WB);
- if (!nvdev->memmap) {
+ if (!memregion->memmap) {
+ memregion->memmap = memremap(memregion->memphys, memregion->memlength, MEMREMAP_WB);
+ if (!memregion->memmap) {
mutex_unlock(&nvdev->memmap_lock);
return -ENOMEM;
}
@@ -256,10 +311,10 @@ static int nvgrace_gpu_memmap(struct nvgrace_gpu_vfio_pci_core_device *nvdev)
*/
static ssize_t
nvgrace_gpu_read_mem(void __user *buf, size_t count, loff_t *ppos,
- struct nvgrace_gpu_vfio_pci_core_device *nvdev)
+ struct mem_region memregion)
{
u64 offset = *ppos & VFIO_PCI_OFFSET_MASK;
- size_t mem_count, i, bar_size = roundup_pow_of_two(nvdev->memlength);
+ size_t mem_count, i, bar_size = roundup_pow_of_two(memregion.memlength);
u8 val = 0xFF;
if (offset >= bar_size)
@@ -273,16 +328,16 @@ nvgrace_gpu_read_mem(void __user *buf, size_t count, loff_t *ppos,
* Read request beyond the actual device memory size is filled with ~0,
* while those beyond the actual reported size is skipped.
*/
- if (offset >= nvdev->memlength)
+ if (offset >= memregion.memlength)
mem_count = 0;
else
- mem_count = min(count, nvdev->memlength - (size_t)offset);
+ mem_count = min(count, memregion.memlength - (size_t)offset);
/*
* Handle read on the BAR2 region. Map to the target device memory
* physical address and copy to the request read buffer.
*/
- if (copy_to_user(buf, (u8 *)nvdev->memmap + offset, mem_count))
+ if (copy_to_user(buf, (u8 *)memregion.memmap + offset, mem_count))
return -EFAULT;
/*
@@ -308,10 +363,16 @@ static ssize_t pcibar_read_emu(struct nvgrace_gpu_vfio_pci_core_device *nvdev,
switch (pos) {
case PCI_BASE_ADDRESS_2:
- val = nvdev->bar_regs[0];
+ val = nvdev->resmem.bar_regs[0];
break;
case PCI_BASE_ADDRESS_3:
- val = nvdev->bar_regs[1];
+ val = nvdev->resmem.bar_regs[1];
+ break;
+ case PCI_BASE_ADDRESS_4:
+ val = nvdev->usemem.bar_regs[0];
+ break;
+ case PCI_BASE_ADDRESS_5:
+ val = nvdev->usemem.bar_regs[1];
break;
}
@@ -329,14 +390,19 @@ static ssize_t nvgrace_gpu_vfio_pci_read(struct vfio_device *core_vdev,
struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
core_vdev, struct nvgrace_gpu_vfio_pci_core_device,
core_device.vdev);
+ struct mem_region memregion;
int ret;
- if (index == VFIO_PCI_BAR2_REGION_INDEX) {
- ret = nvgrace_gpu_memmap(nvdev);
+ if (nvgrace_gpu_vfio_pci_is_fake_bar(index)) {
+ ret = nvgrace_gpu_vfio_pci_get_mem_region(index, nvdev, &memregion);
+ if (ret)
+ return ret;
+
+ ret = nvgrace_gpu_memmap(nvdev, &memregion);
if (ret)
return ret;
- return nvgrace_gpu_read_mem(buf, count, ppos, nvdev);
+ return nvgrace_gpu_read_mem(buf, count, ppos, memregion);
}
if (is_fake_bar_pcicfg_emu_reg_access(*ppos))
@@ -358,10 +424,10 @@ static ssize_t nvgrace_gpu_vfio_pci_read(struct vfio_device *core_vdev,
*/
static ssize_t
nvgrace_gpu_write_mem(size_t count, loff_t *ppos, const void __user *buf,
- struct nvgrace_gpu_vfio_pci_core_device *nvdev)
+ struct mem_region memregion)
{
u64 offset = *ppos & VFIO_PCI_OFFSET_MASK;
- size_t mem_count, bar_size = roundup_pow_of_two(nvdev->memlength);
+ size_t mem_count, bar_size = roundup_pow_of_two(memregion.memlength);
if (offset >= bar_size)
return -EINVAL;
@@ -373,10 +439,10 @@ nvgrace_gpu_write_mem(size_t count, loff_t *ppos, const void __user *buf,
* Determine how many bytes to be actually written to the device memory.
* Do not write to the offset beyond available size.
*/
- if (offset >= nvdev->memlength)
+ if (offset >= memregion.memlength)
goto exitfn;
- mem_count = min(count, nvdev->memlength - (size_t)offset);
+ mem_count = min(count, memregion.memlength - (size_t)offset);
/*
* Only the device memory present on the hardware is mapped, which may
@@ -384,7 +450,7 @@ nvgrace_gpu_write_mem(size_t count, loff_t *ppos, const void __user *buf,
* access outside the available device memory on the hardware. Drop
* those write requests.
*/
- if (copy_from_user((u8 *)nvdev->memmap + offset, buf, mem_count))
+ if (copy_from_user((u8 *)memregion.memmap + offset, buf, mem_count))
return -EFAULT;
exitfn:
@@ -405,25 +471,40 @@ static ssize_t pcibar_write_emu(struct nvgrace_gpu_vfio_pci_core_device *nvdev,
if (copy_from_user(&val, buf, count))
return -EFAULT;
- size = ~(roundup_pow_of_two(nvdev->memlength) - 1);
-
if (val == 0xffffffff) {
switch (pos) {
case PCI_BASE_ADDRESS_2:
- nvdev->bar_regs[0] = (size & GENMASK(31, 4)) |
- (nvdev->bar_regs[0] & GENMASK(3, 0));
+ size = ~(roundup_pow_of_two(nvdev->resmem.memlength) - 1);
+ nvdev->resmem.bar_regs[0] = (size & GENMASK(31, 4)) |
+ (nvdev->resmem.bar_regs[0] & GENMASK(3, 0));
break;
case PCI_BASE_ADDRESS_3:
- nvdev->bar_regs[1] = size >> 32;
+ size = ~(roundup_pow_of_two(nvdev->resmem.memlength) - 1);
+ nvdev->resmem.bar_regs[1] = size >> 32;
+ break;
+ case PCI_BASE_ADDRESS_4:
+ size = ~(roundup_pow_of_two(nvdev->usemem.memlength) - 1);
+ nvdev->usemem.bar_regs[0] = (size & GENMASK(31, 4)) |
+ (nvdev->usemem.bar_regs[0] & GENMASK(3, 0));
+ break;
+ case PCI_BASE_ADDRESS_5:
+ size = ~(roundup_pow_of_two(nvdev->usemem.memlength) - 1);
+ nvdev->usemem.bar_regs[1] = size >> 32;
break;
}
} else {
switch (pos) {
case PCI_BASE_ADDRESS_2:
- nvdev->bar_regs[0] = val;
+ nvdev->resmem.bar_regs[0] = val;
break;
case PCI_BASE_ADDRESS_3:
- nvdev->bar_regs[1] = val;
+ nvdev->resmem.bar_regs[1] = val;
+ break;
+ case PCI_BASE_ADDRESS_4:
+ nvdev->usemem.bar_regs[0] = val;
+ break;
+ case PCI_BASE_ADDRESS_5:
+ nvdev->usemem.bar_regs[1] = val;
break;
}
}
@@ -438,14 +519,19 @@ static ssize_t nvgrace_gpu_vfio_pci_write(struct vfio_device *core_vdev,
unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev);
+ struct mem_region memregion;
int ret;
- if (index == VFIO_PCI_BAR2_REGION_INDEX) {
- ret = nvgrace_gpu_memmap(nvdev);
+ if (nvgrace_gpu_vfio_pci_is_fake_bar(index)) {
+ ret = nvgrace_gpu_vfio_pci_get_mem_region(index, nvdev, &memregion);
if (ret)
return ret;
- return nvgrace_gpu_write_mem(count, ppos, buf, nvdev);
+ ret = nvgrace_gpu_memmap(nvdev, &memregion);
+ if (ret)
+ return ret;
+
+ return nvgrace_gpu_write_mem(count, ppos, buf, memregion);
}
if (is_fake_bar_pcicfg_emu_reg_access(*ppos))
@@ -499,8 +585,6 @@ nvgrace_gpu_vfio_pci_fetch_memory_property(struct pci_dev *pdev,
if (memphys > type_max(phys_addr_t))
return -EOVERFLOW;
- nvdev->memphys = memphys;
-
ret = device_property_read_u64(&pdev->dev, "nvidia,gpu-mem-size",
&(memlength));
if (ret)
@@ -516,8 +600,44 @@ nvgrace_gpu_vfio_pci_fetch_memory_property(struct pci_dev *pdev,
if (memlength == 0)
return -ENOMEM;
- nvdev->memlength = memlength;
+ /*
+ * The VM GPU device driver needs a non-cacheable region to support
+ * the MIG feature. Since the device memory is mapped as NORMAL cached,
+ * carve out a region from the end with a different NORMAL_NC
+ * property (called as reserved memory and represented as resmem). This
+ * region then is exposed as a 64b BAR (region 2 and 3) to the VM, while
+ * exposing the rest (termed as usable memory and represented using usemem)
+ * as cacheable 64b BAR (region 4 and 5).
+ *
+ * devmem (memlength)
+ * |-------------------------------------------------|
+ * | |
+ * usemem.phys/memphys resmem.phys
+ */
+ nvdev->usemem.memphys = memphys;
+
+ /*
+ * The device memory exposed to the VM is added to the kernel by the
+ * VM driver module in chunks of memory block size. Only the usable
+ * memory (usemem) is added to the kernel for usage by the VM
+ * workloads. Make the usable memory size memblock aligned.
+ */
+ if (check_sub_overflow(memlength, RESMEM_SIZE,
+ &nvdev->usemem.memlength)) {
+ ret = -EOVERFLOW;
+ goto done;
+ }
+ nvdev->usemem.memlength = round_down(nvdev->usemem.memlength,
+ MEMBLK_SIZE);
+ if ((check_add_overflow(nvdev->usemem.memphys,
+ nvdev->usemem.memlength, &nvdev->resmem.memphys)) ||
+ (check_sub_overflow(memlength, nvdev->usemem.memlength,
+ &nvdev->resmem.memlength))) {
+ ret = -EOVERFLOW;
+ goto done;
+ }
+done:
return ret;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH v1 1/1] vfio/nvgrace-gpu: carve out non cached reserved region from device memory
2023-11-15 8:07 [PATCH v1 1/1] vfio/nvgrace-gpu: carve out non cached reserved region from device memory ankita
@ 2023-11-27 21:28 ` Alex Williamson
0 siblings, 0 replies; 2+ messages in thread
From: Alex Williamson @ 2023-11-27 21:28 UTC (permalink / raw)
To: ankita
Cc: jgg, yishaih, shameerali.kolothum.thodi, kevin.tian, aniketa,
cjia, kwankhede, targupta, vsethi, acurrid, apopple, jhubbard,
danw, anuaggarwal, kvm, linux-kernel, benh
[Cc +benh]
On Wed, 15 Nov 2023 13:37:51 +0530
<ankita@nvidia.com> wrote:
> From: Ankit Agrawal <ankita@nvidia.com>
>
> The NVIDIA's upcoming Grace Hopper Superchip GPU device driver has a
> requirement of a reserved 1G uncached RAM-like region to support the
> Multi-Instance GPU (MIG) feature [1]. Carve out the region from the device
> memory.
>
> Based on [2], the requisite properties (uncached, unaligned access) can be
> achieved through a VM mapping (S1) of NORMAL_NC and host (S2) mapping
> with MemAttr[2:0]=0b101. Currently there is no provision in KVM for a S2
> mapping with MemAttr[2:0]=0b101, but there is an ongoing effort to provide
> the same [3].
>
> This patch change goes on top of the VFIO PCI variant driver proposed for
> the Grace Hopper devices in [4], which facilitates the entire device memory
> to be mapped as NORMAL in S2. To provide a different non-cached property to
> the reserved 1G region, it needs to be carved out from the device memory and
> mapped as a separate region in Qemu VMA with pgprot_writecombine().
> pgprot_writecombine() sets the Qemu VMA page properties (pgprot) as
> NORMAL_NC. Using the proposed changes in [5] and [3], KVM marks the region
> with MemAttr[2:0]=0b101 in S2.
>
> The new region (represented as resmem in the patch) is carved out from
> the tail end of the device memory host physical address range and exposed
> as a 64b BAR (comprising of region 2 and 3) to the VM.
>
> The remaining device memory (termed as usable memory and represented
> using usemem) continues to be NORMAL cacheable and is exposed as 64b BAR
> with region 4 and 5. This memory is added by the VM Nvidia device driver [6]
> to the VM kernel as memblocks. Hence make the usable memory size memblock
> aligned.
Couldn't we make use of the sparse memory capability to force userspace
to create separate mappings? ie. abutting mmap'able ranges within a
single BAR.
I'd also suggest that this seems like a fundamental feature of the
nvgrace-gpu variant driver, this should be rolled in or minimally sent
as a series together.
>
> The memory layout on the host looks like the following:
> devmem (memlength)
> |--------------------------------------------------|
> |-------------cached------------------------|--NC--|
> | |
> usemem.phys/memphys resmem.phys
>
> [1] https://www.nvidia.com/en-in/technologies/multi-instance-gpu/
> [2] section D8.5.5 of DDI0487_I_a_a-profile_architecture_reference_manual.pdf
This is not a link (obviously) and I only come up with a
DDI0487J_a_a-profile_architecture_reference_manual.pdf when searching.
> [3] https://lore.kernel.org/all/20230907181459.18145-3-ankita@nvidia.com/
> [4] https://lore.kernel.org/all/20231114081611.30550-1-ankita@nvidia.com/
> [5] https://lore.kernel.org/all/20230907181459.18145-2-ankita@nvidia.com/
> [6] https://github.com/NVIDIA/open-gpu-kernel-modules
>
> Signed-off-by: Ankit Agrawal <ankita@nvidia.com>
> ---
> drivers/vfio/pci/nvgrace-gpu/main.c | 236 +++++++++++++++++++++-------
> 1 file changed, 178 insertions(+), 58 deletions(-)
>
> diff --git a/drivers/vfio/pci/nvgrace-gpu/main.c b/drivers/vfio/pci/nvgrace-gpu/main.c
> index a3dbee6b87de..87afbda39939 100644
> --- a/drivers/vfio/pci/nvgrace-gpu/main.c
> +++ b/drivers/vfio/pci/nvgrace-gpu/main.c
> @@ -7,24 +7,62 @@
> #include <linux/vfio_pci_core.h>
> #include <linux/vfio.h>
>
> +/* Memory size expected as non cached and reserved by the VM driver */
> +#define RESMEM_SIZE 0x40000000
> +#define MEMBLK_SIZE 0x20000000
> +
> +struct mem_region {
> + phys_addr_t memphys; /* Base address of the region */
> + size_t memlength; /* Region size */
> + u32 bar_regs[2]; /* Emulated BAR offset registers */
> + void *memmap; /* Memremap pointer to the region */
Don't we need an __iomem pointer to the non-cached region as well as
calls to ioremap() and iounmap() here somewhere?
> +};
> +
> struct nvgrace_gpu_vfio_pci_core_device {
> struct vfio_pci_core_device core_device;
> - phys_addr_t memphys;
> - size_t memlength;
> - u32 bar_regs[2];
> - void *memmap;
> + /* Cached and usable memory for the VM. */
> + struct mem_region usemem;
> + /* Non cached memory carved out from the end of device memory */
> + struct mem_region resmem;
> struct mutex memmap_lock;
> };
>
> +/* Choose the structure corresponding to the BAR under question. */
> +static int nvgrace_gpu_vfio_pci_get_mem_region(int index,
> + struct nvgrace_gpu_vfio_pci_core_device *nvdev,
> + struct mem_region *region)
> +{
> + if (index == VFIO_PCI_BAR4_REGION_INDEX)
> + *region = nvdev->usemem;
> + else if (index == VFIO_PCI_BAR2_REGION_INDEX)
> + *region = nvdev->resmem;
> + else
> + return -EINVAL;
> +
> + return 0;
> +}
> +
> +static bool nvgrace_gpu_vfio_pci_is_fake_bar(int index)
> +{
> + if (index == VFIO_PCI_BAR2_REGION_INDEX ||
> + index == VFIO_PCI_BAR4_REGION_INDEX)
> + return true;
> +
> + return false;
> +}
> +
> static void init_fake_bar_emu_regs(struct vfio_device *core_vdev)
> {
> struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
> core_vdev, struct nvgrace_gpu_vfio_pci_core_device,
> core_device.vdev);
>
> - nvdev->bar_regs[0] = PCI_BASE_ADDRESS_MEM_TYPE_64 |
> - PCI_BASE_ADDRESS_MEM_PREFETCH;
> - nvdev->bar_regs[1] = 0;
> + nvdev->resmem.bar_regs[0] = PCI_BASE_ADDRESS_MEM_TYPE_64 |
> + PCI_BASE_ADDRESS_MEM_PREFETCH;
> + nvdev->resmem.bar_regs[1] = 0;
> + nvdev->usemem.bar_regs[0] = PCI_BASE_ADDRESS_MEM_TYPE_64 |
> + PCI_BASE_ADDRESS_MEM_PREFETCH;
> + nvdev->usemem.bar_regs[1] = 0;
> }
>
> static bool is_fake_bar_pcicfg_emu_reg_access(loff_t pos)
> @@ -33,7 +71,7 @@ static bool is_fake_bar_pcicfg_emu_reg_access(loff_t pos)
> u64 offset = pos & VFIO_PCI_OFFSET_MASK;
>
> if ((index == VFIO_PCI_CONFIG_REGION_INDEX) &&
> - (offset == PCI_BASE_ADDRESS_2 || offset == PCI_BASE_ADDRESS_3))
> + (offset >= PCI_BASE_ADDRESS_2 && offset <= PCI_BASE_ADDRESS_5))
> return true;
>
> return false;
> @@ -67,9 +105,9 @@ static void nvgrace_gpu_vfio_pci_close_device(struct vfio_device *core_vdev)
> core_vdev, struct nvgrace_gpu_vfio_pci_core_device,
> core_device.vdev);
>
> - if (nvdev->memmap) {
> - memunmap(nvdev->memmap);
> - nvdev->memmap = NULL;
> + if (nvdev->usemem.memmap) {
> + memunmap(nvdev->usemem.memmap);
> + nvdev->usemem.memmap = NULL;
> }
>
> mutex_destroy(&nvdev->memmap_lock);
> @@ -78,7 +116,7 @@ static void nvgrace_gpu_vfio_pci_close_device(struct vfio_device *core_vdev)
> }
>
> static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
> - struct vm_area_struct *vma)
> + struct vm_area_struct *vma)
spurious
> {
> struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
> core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev);
> @@ -87,11 +125,17 @@ static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
> unsigned int index;
> u64 req_len, pgoff, end;
> int ret = 0;
> + struct mem_region memregion;
>
> index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
> - if (index != VFIO_PCI_BAR2_REGION_INDEX)
> +
> + if (!nvgrace_gpu_vfio_pci_is_fake_bar(index))
> return vfio_pci_core_mmap(core_vdev, vma);
>
> + ret = nvgrace_gpu_vfio_pci_get_mem_region(index, nvdev, &memregion);
> + if (ret)
> + return ret;
> +
> /*
> * Request to mmap the BAR. Map to the CPU accessible memory on the
> * GPU using the memory information gathered from the system ACPI
> @@ -101,7 +145,7 @@ static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
> ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
>
> if (check_sub_overflow(vma->vm_end, vma->vm_start, &req_len) ||
> - check_add_overflow(PHYS_PFN(nvdev->memphys), pgoff, &start_pfn) ||
> + check_add_overflow(PHYS_PFN(memregion.memphys), pgoff, &start_pfn) ||
> check_add_overflow(PFN_PHYS(pgoff), req_len, &end))
> return -EOVERFLOW;
>
> @@ -109,9 +153,16 @@ static int nvgrace_gpu_vfio_pci_mmap(struct vfio_device *core_vdev,
> * Check that the mapping request does not go beyond available device
> * memory size
> */
> - if (end > nvdev->memlength)
> + if (end > memregion.memlength)
> return -EINVAL;
>
> + /*
> + * The carved out region of the device memory needs the NORMAL_NC
> + * property. Communicate as such to the hypervisor.
> + */
> + if (index == VFIO_PCI_BAR2_REGION_INDEX)
> + vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> +
> /*
> * Perform a PFN map to the memory and back the device BAR by the
> * GPU memory.
> @@ -142,7 +193,12 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> unsigned long minsz = offsetofend(struct vfio_region_info, offset);
> struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
> core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev);
> + struct vfio_region_info_cap_sparse_mmap *sparse;
> + struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
> struct vfio_region_info info;
> + struct mem_region memregion;
> + uint32_t size;
> + int ret;
>
> if (copy_from_user(&info, (void __user *)arg, minsz))
> return -EFAULT;
> @@ -150,16 +206,14 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> if (info.argsz < minsz)
> return -EINVAL;
>
> - if (info.index == VFIO_PCI_BAR2_REGION_INDEX) {
> + if (nvgrace_gpu_vfio_pci_is_fake_bar(info.index)) {
> + ret = nvgrace_gpu_vfio_pci_get_mem_region(info.index, nvdev, &memregion);
> + if (ret)
> + return ret;
> /*
> * Request to determine the BAR region information. Send the
> * GPU memory information.
> */
> - uint32_t size;
> - int ret;
> - struct vfio_region_info_cap_sparse_mmap *sparse;
> - struct vfio_info_cap caps = { .buf = NULL, .size = 0 };
> -
> size = struct_size(sparse, areas, 1);
>
> /*
> @@ -173,7 +227,7 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
>
> sparse->nr_areas = 1;
> sparse->areas[0].offset = 0;
> - sparse->areas[0].size = nvdev->memlength;
> + sparse->areas[0].size = memregion.memlength;
> sparse->header.id = VFIO_REGION_INFO_CAP_SPARSE_MMAP;
> sparse->header.version = 1;
>
> @@ -188,7 +242,7 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> * Given that the memory is exposed as a BAR and may not be
> * aligned, roundup to the next power-of-2.
> */
> - info.size = roundup_pow_of_two(nvdev->memlength);
> + info.size = roundup_pow_of_two(memregion.memlength);
> info.flags = VFIO_REGION_INFO_FLAG_READ |
> VFIO_REGION_INFO_FLAG_WRITE |
> VFIO_REGION_INFO_FLAG_MMAP;
> @@ -201,8 +255,8 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> } else {
> vfio_info_cap_shift(&caps, sizeof(info));
> if (copy_to_user((void __user *)arg +
> - sizeof(info), caps.buf,
> - caps.size)) {
> + sizeof(info), caps.buf,
> + caps.size)) {
> kfree(caps.buf);
> return -EFAULT;
> }
> @@ -211,7 +265,7 @@ nvgrace_gpu_vfio_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> kfree(caps.buf);
> }
> return copy_to_user((void __user *)arg, &info, minsz) ?
> - -EFAULT : 0;
> + -EFAULT : 0;
> }
> return vfio_pci_core_ioctl(core_vdev, VFIO_DEVICE_GET_REGION_INFO, arg);
> }
> @@ -228,12 +282,13 @@ static long nvgrace_gpu_vfio_pci_ioctl(struct vfio_device *core_vdev,
> return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> }
>
> -static int nvgrace_gpu_memmap(struct nvgrace_gpu_vfio_pci_core_device *nvdev)
> +static int nvgrace_gpu_memmap(struct nvgrace_gpu_vfio_pci_core_device *nvdev,
> + struct mem_region *memregion)
> {
> mutex_lock(&nvdev->memmap_lock);
> - if (!nvdev->memmap) {
> - nvdev->memmap = memremap(nvdev->memphys, nvdev->memlength, MEMREMAP_WB);
> - if (!nvdev->memmap) {
> + if (!memregion->memmap) {
> + memregion->memmap = memremap(memregion->memphys, memregion->memlength, MEMREMAP_WB);
> + if (!memregion->memmap) {
> mutex_unlock(&nvdev->memmap_lock);
> return -ENOMEM;
> }
> @@ -256,10 +311,10 @@ static int nvgrace_gpu_memmap(struct nvgrace_gpu_vfio_pci_core_device *nvdev)
> */
> static ssize_t
> nvgrace_gpu_read_mem(void __user *buf, size_t count, loff_t *ppos,
> - struct nvgrace_gpu_vfio_pci_core_device *nvdev)
> + struct mem_region memregion)
> {
> u64 offset = *ppos & VFIO_PCI_OFFSET_MASK;
> - size_t mem_count, i, bar_size = roundup_pow_of_two(nvdev->memlength);
> + size_t mem_count, i, bar_size = roundup_pow_of_two(memregion.memlength);
> u8 val = 0xFF;
>
> if (offset >= bar_size)
> @@ -273,16 +328,16 @@ nvgrace_gpu_read_mem(void __user *buf, size_t count, loff_t *ppos,
> * Read request beyond the actual device memory size is filled with ~0,
> * while those beyond the actual reported size is skipped.
> */
> - if (offset >= nvdev->memlength)
> + if (offset >= memregion.memlength)
> mem_count = 0;
> else
> - mem_count = min(count, nvdev->memlength - (size_t)offset);
> + mem_count = min(count, memregion.memlength - (size_t)offset);
>
> /*
> * Handle read on the BAR2 region. Map to the target device memory
> * physical address and copy to the request read buffer.
> */
> - if (copy_to_user(buf, (u8 *)nvdev->memmap + offset, mem_count))
> + if (copy_to_user(buf, (u8 *)memregion.memmap + offset, mem_count))
> return -EFAULT;
>
> /*
> @@ -308,10 +363,16 @@ static ssize_t pcibar_read_emu(struct nvgrace_gpu_vfio_pci_core_device *nvdev,
>
> switch (pos) {
> case PCI_BASE_ADDRESS_2:
> - val = nvdev->bar_regs[0];
> + val = nvdev->resmem.bar_regs[0];
> break;
> case PCI_BASE_ADDRESS_3:
> - val = nvdev->bar_regs[1];
> + val = nvdev->resmem.bar_regs[1];
> + break;
> + case PCI_BASE_ADDRESS_4:
> + val = nvdev->usemem.bar_regs[0];
> + break;
> + case PCI_BASE_ADDRESS_5:
> + val = nvdev->usemem.bar_regs[1];
> break;
> }
>
> @@ -329,14 +390,19 @@ static ssize_t nvgrace_gpu_vfio_pci_read(struct vfio_device *core_vdev,
> struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
> core_vdev, struct nvgrace_gpu_vfio_pci_core_device,
> core_device.vdev);
> + struct mem_region memregion;
> int ret;
>
> - if (index == VFIO_PCI_BAR2_REGION_INDEX) {
> - ret = nvgrace_gpu_memmap(nvdev);
> + if (nvgrace_gpu_vfio_pci_is_fake_bar(index)) {
> + ret = nvgrace_gpu_vfio_pci_get_mem_region(index, nvdev, &memregion);
> + if (ret)
> + return ret;
> +
> + ret = nvgrace_gpu_memmap(nvdev, &memregion);
> if (ret)
> return ret;
>
> - return nvgrace_gpu_read_mem(buf, count, ppos, nvdev);
> + return nvgrace_gpu_read_mem(buf, count, ppos, memregion);
> }
>
> if (is_fake_bar_pcicfg_emu_reg_access(*ppos))
> @@ -358,10 +424,10 @@ static ssize_t nvgrace_gpu_vfio_pci_read(struct vfio_device *core_vdev,
> */
> static ssize_t
> nvgrace_gpu_write_mem(size_t count, loff_t *ppos, const void __user *buf,
> - struct nvgrace_gpu_vfio_pci_core_device *nvdev)
> + struct mem_region memregion)
> {
> u64 offset = *ppos & VFIO_PCI_OFFSET_MASK;
> - size_t mem_count, bar_size = roundup_pow_of_two(nvdev->memlength);
> + size_t mem_count, bar_size = roundup_pow_of_two(memregion.memlength);
>
> if (offset >= bar_size)
> return -EINVAL;
> @@ -373,10 +439,10 @@ nvgrace_gpu_write_mem(size_t count, loff_t *ppos, const void __user *buf,
> * Determine how many bytes to be actually written to the device memory.
> * Do not write to the offset beyond available size.
> */
> - if (offset >= nvdev->memlength)
> + if (offset >= memregion.memlength)
> goto exitfn;
>
> - mem_count = min(count, nvdev->memlength - (size_t)offset);
> + mem_count = min(count, memregion.memlength - (size_t)offset);
>
> /*
> * Only the device memory present on the hardware is mapped, which may
> @@ -384,7 +450,7 @@ nvgrace_gpu_write_mem(size_t count, loff_t *ppos, const void __user *buf,
> * access outside the available device memory on the hardware. Drop
> * those write requests.
> */
> - if (copy_from_user((u8 *)nvdev->memmap + offset, buf, mem_count))
> + if (copy_from_user((u8 *)memregion.memmap + offset, buf, mem_count))
> return -EFAULT;
>
> exitfn:
> @@ -405,25 +471,40 @@ static ssize_t pcibar_write_emu(struct nvgrace_gpu_vfio_pci_core_device *nvdev,
> if (copy_from_user(&val, buf, count))
> return -EFAULT;
>
> - size = ~(roundup_pow_of_two(nvdev->memlength) - 1);
> -
> if (val == 0xffffffff) {
> switch (pos) {
> case PCI_BASE_ADDRESS_2:
> - nvdev->bar_regs[0] = (size & GENMASK(31, 4)) |
> - (nvdev->bar_regs[0] & GENMASK(3, 0));
> + size = ~(roundup_pow_of_two(nvdev->resmem.memlength) - 1);
> + nvdev->resmem.bar_regs[0] = (size & GENMASK(31, 4)) |
> + (nvdev->resmem.bar_regs[0] & GENMASK(3, 0));
> break;
> case PCI_BASE_ADDRESS_3:
> - nvdev->bar_regs[1] = size >> 32;
> + size = ~(roundup_pow_of_two(nvdev->resmem.memlength) - 1);
> + nvdev->resmem.bar_regs[1] = size >> 32;
> + break;
> + case PCI_BASE_ADDRESS_4:
> + size = ~(roundup_pow_of_two(nvdev->usemem.memlength) - 1);
> + nvdev->usemem.bar_regs[0] = (size & GENMASK(31, 4)) |
> + (nvdev->usemem.bar_regs[0] & GENMASK(3, 0));
> + break;
> + case PCI_BASE_ADDRESS_5:
> + size = ~(roundup_pow_of_two(nvdev->usemem.memlength) - 1);
> + nvdev->usemem.bar_regs[1] = size >> 32;
> break;
> }
> } else {
> switch (pos) {
> case PCI_BASE_ADDRESS_2:
> - nvdev->bar_regs[0] = val;
> + nvdev->resmem.bar_regs[0] = val;
> break;
> case PCI_BASE_ADDRESS_3:
> - nvdev->bar_regs[1] = val;
> + nvdev->resmem.bar_regs[1] = val;
> + break;
> + case PCI_BASE_ADDRESS_4:
> + nvdev->usemem.bar_regs[0] = val;
> + break;
> + case PCI_BASE_ADDRESS_5:
> + nvdev->usemem.bar_regs[1] = val;
> break;
> }
> }
> @@ -438,14 +519,19 @@ static ssize_t nvgrace_gpu_vfio_pci_write(struct vfio_device *core_vdev,
> unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> struct nvgrace_gpu_vfio_pci_core_device *nvdev = container_of(
> core_vdev, struct nvgrace_gpu_vfio_pci_core_device, core_device.vdev);
> + struct mem_region memregion;
> int ret;
>
> - if (index == VFIO_PCI_BAR2_REGION_INDEX) {
> - ret = nvgrace_gpu_memmap(nvdev);
> + if (nvgrace_gpu_vfio_pci_is_fake_bar(index)) {
> + ret = nvgrace_gpu_vfio_pci_get_mem_region(index, nvdev, &memregion);
> if (ret)
> return ret;
>
> - return nvgrace_gpu_write_mem(count, ppos, buf, nvdev);
> + ret = nvgrace_gpu_memmap(nvdev, &memregion);
> + if (ret)
> + return ret;
> +
> + return nvgrace_gpu_write_mem(count, ppos, buf, memregion);
> }
>
> if (is_fake_bar_pcicfg_emu_reg_access(*ppos))
> @@ -499,8 +585,6 @@ nvgrace_gpu_vfio_pci_fetch_memory_property(struct pci_dev *pdev,
> if (memphys > type_max(phys_addr_t))
> return -EOVERFLOW;
>
> - nvdev->memphys = memphys;
> -
> ret = device_property_read_u64(&pdev->dev, "nvidia,gpu-mem-size",
> &(memlength));
> if (ret)
> @@ -516,8 +600,44 @@ nvgrace_gpu_vfio_pci_fetch_memory_property(struct pci_dev *pdev,
> if (memlength == 0)
> return -ENOMEM;
>
> - nvdev->memlength = memlength;
> + /*
> + * The VM GPU device driver needs a non-cacheable region to support
> + * the MIG feature. Since the device memory is mapped as NORMAL cached,
> + * carve out a region from the end with a different NORMAL_NC
> + * property (called as reserved memory and represented as resmem). This
> + * region then is exposed as a 64b BAR (region 2 and 3) to the VM, while
> + * exposing the rest (termed as usable memory and represented using usemem)
> + * as cacheable 64b BAR (region 4 and 5).
> + *
> + * devmem (memlength)
> + * |-------------------------------------------------|
> + * | |
> + * usemem.phys/memphys resmem.phys
> + */
> + nvdev->usemem.memphys = memphys;
> +
> + /*
> + * The device memory exposed to the VM is added to the kernel by the
> + * VM driver module in chunks of memory block size. Only the usable
> + * memory (usemem) is added to the kernel for usage by the VM
> + * workloads. Make the usable memory size memblock aligned.
> + */
> + if (check_sub_overflow(memlength, RESMEM_SIZE,
> + &nvdev->usemem.memlength)) {
> + ret = -EOVERFLOW;
> + goto done;
> + }
> + nvdev->usemem.memlength = round_down(nvdev->usemem.memlength,
> + MEMBLK_SIZE);
> + if ((check_add_overflow(nvdev->usemem.memphys,
> + nvdev->usemem.memlength, &nvdev->resmem.memphys)) ||
> + (check_sub_overflow(memlength, nvdev->usemem.memlength,
> + &nvdev->resmem.memlength))) {
> + ret = -EOVERFLOW;
> + goto done;
> + }
>
> +done:
> return ret;
> }
>
The second emulated BAR only exemplifies the issues with the BAR
handling noted in the v13 nvgrace-gpu driver and it doesn't seem like
the semantics of the non-cached read/write accesses have really been
considered since we're still creating a write-back memremap() access
through that path. Thanks,
Alex
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2023-11-15 8:07 [PATCH v1 1/1] vfio/nvgrace-gpu: carve out non cached reserved region from device memory ankita
2023-11-27 21:28 ` Alex Williamson
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