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, 12 insertions, 0 deletions

diff --git a/kernel/gsp_emulation.c b/kernel/gsp_emulation.c
index 0b6bba0..969d4fd 100644
--- a/kernel/gsp_emulation.c
+++ b/kernel/gsp_emulation.c
@@ -305,6 +305,18 @@ static void gsp_emu_poll_boot(struct gsp_emu_context *ctx)
 		}
 	}
 
+	/* Temporary: watch the PCFG link-caps mirror for guest writes */
+	{
+		static u32 last_linkcap;
+		u32 v = gsp_emu_shadow_read32(ctx, 0x88084);
+
+		if (v != last_linkcap) {
+			nv_vgpu_info(ctx->vgpu, "GSP-BOOT: PCFG[0x88084] = 0x%x (was 0x%x)",
+				     v, last_linkcap);
+			last_linkcap = v;
+		}
+	}
+
 	/* GSP ENGINE reset asserted -> falcon rebooted, restart stage tracking */
 	if ((engine & 0x1) && ctx->boot_stage != GSP_BOOT_STAGE_IDLE) {
 		nv_vgpu_info(ctx->vgpu, "GSP-BOOT: falcon reset, back to IDLE");