/* Copyright 2024 Joshua Bakita
* Helpers for dealing with the PCIe and platform bus
*
* = Design Notes =
* We have to use PRAMIN to access the BAR2 page table. While it's typically also
* mapped into BAR2, we have no way to know where without the table. If the table
* changes, the new sections will have new mappings in BAR2, repeating the
* problem, and making caching insufficient.
*
* = Terms =
* VRAM/VID_MEM: Video RAM; Addresses to physical frames in the on-GPU RAM.
* SYS_MEM: System Memory; "Bus addresses"; Addresses which can be presented to
* the PCIe Host for resolution. On x86_64 without an IOMMU, these are
* just physical addresses, but may be I/O Virtual Addresses (IOVAs)
* or translated via an I/O MMU on other platforms; DMA Addresses.
* PEER: Addresses to RAM on another GPU.
*/
#include <linux/printk.h> // For printk()
#include <asm/errno.h> // For error defines
#include <asm/io.h> // For readl()
#include "nvdebug.h"
/* Obtain the PRAMIN offset at which `addr` can be accessed
@param addr Address to find
@param target Which address space to use (VRAM, SYS_MEM, PEER(?))
@return positive offset or -EINVAL on invalid arguments
Note: Will move the PRAMIN window to accomodate the request. Only guarantees
that the surrounding 64KiB window will be accessible.
Note: Moving the PRAMIN window will cause problems if it races with driver
code that tries to do the same, or expects the window not to move.
Bugs: Untested on PEER.
*/
int addr_to_pramin_mut(struct nvdebug_state *g,
uint64_t addr, enum INST_TARGET target) {
bar0_window_t window;
uint64_t pramin_base;
// For us, accuracy and robustness is more important than speed
// Check that the address is valid (49 bits are addressable on-GPU, but
// PRAMIN only supports up to 40 bits).
if (addr & ~0x000000ffffffffff) {
printk(KERN_ERR "[nvdebug] Invalid address %llx passed to %s!\n",
addr, __func__);
return -EINVAL;
}
window.raw = nvdebug_readl(g, NV_PBUS_BAR0_WINDOW);
if (window.target != target)
goto relocate;
pramin_base = ((uint64_t)window.base) << 16;
if (addr < pramin_base || addr > pramin_base + NV_PRAMIN_LEN)
goto relocate;
return addr - pramin_base; // Guaranteed to be < 1MiB, so safe for int
relocate:
printk(KERN_INFO "[nvdebug] Moving PRAMIN win from base %llx to %llx to accomodate %#018llx\n", pramin_base, (addr >> 16) << 16, addr);
// Move PRAMIN window to a 64KiB-aligned address
window.base = (u32)(addr >> 16); // Safe, due to above range check
window.target = target;
nvdebug_writel(g, NV_PBUS_BAR0_WINDOW, window.raw);
// Wait for the window to move by re-reading (as done in nvgpu driver)
(void) nvdebug_readl(g, NV_PBUS_BAR0_WINDOW);
return (int)(addr & 0xffffull);
}
/* Get a copy of the BAR2 page directory configuration (base and aperture)
@param pd Pointer at which to store the configuration, including a pointer
and aperture for the zeroth entry of the top-level page directory
(PD3 for V2 page tables). This pointer **may not** be directly
dereferencable, and the caller may need to shift the BAR2 window.
@return 0 on success, -errno on error.
Note: This may move the PRAMIN window.
*/
int get_bar2_pdb(struct nvdebug_state *g, page_dir_config_t* pd) {
int ret;
bar_config_block_t bar2_block;
if (!pd)
return -EINVAL;
if (!g->bar2)
return -ENXIO;
// BAR2 has its own instance block (typically in VRAM) which contains the
// Page Directory Base (PDB), a pointer to a page directory/table
// hierarchy used to translate BAR2 offsets to VRAM or SYS_MEM addresses.
// Determine location of BAR2 instance block
if ((bar2_block.raw = nvdebug_readl(g, NV_PBUS_BAR2_BLOCK)) == -1) {
printk(KERN_ERR "[nvdebug] Unable to read BAR2/3 configuration! BAR2/3 inaccessible.\n");
return -ENOTSUPP;
}
printk(KERN_INFO "[nvdebug] BAR2 inst block @ %llx in %s's %s address space.\n", ((u64)bar2_block.ptr) << 12, target_to_text(bar2_block.target), bar2_block.is_virtual ? "virtual" : "physical");
// Setup PRAMIN to point at the BAR2 instance block
if ((ret = addr_to_pramin_mut(g, (uint64_t)bar2_block.ptr << 12, bar2_block.target)) < 0) {
printk(KERN_ERR "[nvdebug] Invalid BAR2/3 Instance Block configuration! BAR2/3 inaccessible.\n");
return ret;
}
printk(KERN_INFO "[nvdebug] BAR2 inst block at off %x in PRAMIN\n", ret);
// Pull the page directory base configuration from the instance block
if ((pd->raw = nvdebug_readq(g, NV_PRAMIN + ret + NV_PRAMIN_PDB_CONFIG_OFF)) == -1) {
printk(KERN_ERR "[nvdebug] Unable to read BAR2/3 PDB configuration! BAR2/3 inaccessible.\n");
return -ENOTSUPP;
}
return 0;
}
