kernel: FB/BUS info-list controls + PCIe link caps for the UVM path

CUDA (cuInit) now reaches UVM's device create: libcuda opens nvidia-uvm,
UVM calls nvGpuOpsDeviceCreate/gpuGetGpuInfo, and the driver fails at
getPCIELinkRateMBps -> calculatePCIELinkRateMBps ("Unknown PCIe speed",
NV_ERR_INVALID_STATE) -> nv_open_device aborts -> cuInit returns
CUDA_ERROR_NOT_INITIALIZED (3).

Implemented along the way:
- FB_GET_INFO_V2 (0x20801303): echo the requested FB info indices and
  answer TU104 values (256MB RAM/heap/BAR1, GDDR6, 8 LTCs, 4MB L2, ...).
  Fixes the kern_mem_sys_ctrl.c:911 asserts and gives CUDA/UVM real
  memory sizes.
- BUS_GET_INFO_V2 (0x20801823): echo indices; PCIe Gen3 x16 link caps /
  GEN info / link status, SYSMEM_CONNECTION_TYPE=PCIE. UVM's
  gpuGetSysmemLinkInfo reads SYSMEM_CONNECTION_TYPE and the nominal link
  bandwidth from here.
- PCIe Link Capabilities in the emulated config space (0x8C/0x92) and in
  the BAR0 PCFG mirror (gpuReadBusConfigReg -> NV_PCFG+0x84 = BAR0+
  0x88084): MAX_SPEED=3 (8GT/s Gen3), MAX_WIDTH=0x10 (x16); link status
  mirror at 0x88088. Also mirrored under the VF-window/low aliases.
- Temporary change-watch on PCFG[0x88084] to see if the guest overwrites
  it (it does not - stays 0x103).

Verified: guest nvidia-smi -L still works and reports PCIe Generation
Max/Current = 3. cuInit still fails; the remaining question is which
address the driver's kbifGetGpuLinkCapabilities read sees as zero (the
PCFG shadow holds 0x103). Guest-side kprobe tracing of that function
panicked the VM (free_swap_cache page fault on a corrupted pointer) -
possible guest memory corruption to investigate separately.

1 files changed, 30 insertions, 0 deletions

diff --git a/kernel/bar_emulation.c b/kernel/bar_emulation.c
index eaa006c..3448b8c 100644
--- a/kernel/bar_emulation.c
+++ b/kernel/bar_emulation.c
@@ -280,6 +280,36 @@ int nv_vgpu_bar_emul_init(struct nv_vgpu_device *vgpu)
 	*(u32 *)((u8 *)ctx->bar0_shadow + 0x100ce0) = 0x00000018;
 
 	/*
+	 * NV_PCFG (BAR0+0x88000) - PCI config space mirror the driver reads
+	 * via gpuReadBusConfigReg_HAL (GPU_BUS_CFG_RD32):
+	 *   0x88084 NV_XVE_LINK_CAPABILITIES: MAX_LINK_SPEED 3:0 = 3 (8 GT/s,
+	 *           Gen3), MAX_LINK_WIDTH 9:4 = 0x10 (x16).
+	 *   0x88088 NV_XVE_LINK_CONTROL_STATUS: negotiated speed 19:16 = 3,
+	 *           negotiated width 25:20 = 0x10 (x16).
+	 * UVM's nvGpuOpsDeviceCreate -> getPCIELinkRateMBps ->
+	 * kbifControlGetPCIEInfo -> kbifGetGpuLinkCapabilities reads 0x88084;
+	 * zeros make calculatePCIELinkRateMBps log "Unknown PCIe speed" and
+	 * return NV_ERR_INVALID_STATE, which fails cuInit
+	 * (CUDA_ERROR_NOT_INITIALIZED in the guest).
+	 *
+	 * DEVICE_BASE(NV_PCFG) expands to 0 in this driver (nvmisc.h:
+	 * "#define DEVICE_BASE(d) (0?d)"), so the read is actually
+	 * gpuNvAddr + 0x84 - mirror the values at the low alias as well.
+	 */
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0x88084) = 0x00000103;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0x88088) = 0x01030000;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0x00084) = 0x00000103;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0x00088) = 0x01030000;
+	/* Same values under the VF register window aliases, in case this
+	 * driver reaches the config mirror through virtualRegPhysOffset. */
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0xB80084) = 0x00000103;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0xB80088) = 0x01030000;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0xB88084) = 0x00000103;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0xB88088) = 0x01030000;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0xC08084) = 0x00000103;
+	*(u32 *)((u8 *)ctx->bar0_shadow + 0xC08088) = 0x01030000;
+
+	/*
 	 * Serve a valid VBIOS at the PROM window (BAR0+0x300000).
 	 *
 	 * The guest driver's physical GSP boot (kgspInitRm -> TU102 path)