From 21e00fa55f3fdfcbb20da7c6876c91ef3609b387 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Mon, 31 Oct 2016 09:53:03 -0600 Subject: memory: Replace skip_dump flag with "ram_device" Setting skip_dump on a MemoryRegion allows us to modify one specific code path, but the restriction we're trying to address encompasses more than that. If we have a RAM MemoryRegion backed by a physical device, it not only restricts our ability to dump that region, but also affects how we should manipulate it. Here we recognize that MemoryRegions do not change to sometimes allow dumps and other times not, so we replace setting the skip_dump flag with a new initializer so that we know exactly the type of region to which we're applying this behavior. Signed-off-by: Alex Williamson Acked-by: Paolo Bonzini --- include/exec/memory.h | 41 ++++++++++++++++++++++++++++------------- 1 file changed, 28 insertions(+), 13 deletions(-) (limited to 'include/exec') diff --git a/include/exec/memory.h b/include/exec/memory.h index 79ccaaba1f..a75b8c3465 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -209,7 +209,7 @@ struct MemoryRegion { void (*destructor)(MemoryRegion *mr); uint64_t align; bool terminates; - bool skip_dump; + bool ram_device; bool enabled; bool warning_printed; /* For reservations */ uint8_t vga_logging_count; @@ -448,6 +448,30 @@ void memory_region_init_ram_ptr(MemoryRegion *mr, uint64_t size, void *ptr); +/** + * memory_region_init_ram_device_ptr: Initialize RAM device memory region from + * a user-provided pointer. + * + * A RAM device represents a mapping to a physical device, such as to a PCI + * MMIO BAR of an vfio-pci assigned device. The memory region may be mapped + * into the VM address space and access to the region will modify memory + * directly. However, the memory region should not be included in a memory + * dump (device may not be enabled/mapped at the time of the dump), and + * operations incompatible with manipulating MMIO should be avoided. Replaces + * skip_dump flag. + * + * @mr: the #MemoryRegion to be initialized. + * @owner: the object that tracks the region's reference count + * @name: the name of the region. + * @size: size of the region. + * @ptr: memory to be mapped; must contain at least @size bytes. + */ +void memory_region_init_ram_device_ptr(MemoryRegion *mr, + struct Object *owner, + const char *name, + uint64_t size, + void *ptr); + /** * memory_region_init_alias: Initialize a memory region that aliases all or a * part of another memory region. @@ -574,22 +598,13 @@ static inline bool memory_region_is_ram(MemoryRegion *mr) } /** - * memory_region_is_skip_dump: check whether a memory region should not be - * dumped - * - * Returns %true is a memory region should not be dumped(e.g. VFIO BAR MMAP). + * memory_region_is_ram_device: check whether a memory region is a ram device * - * @mr: the memory region being queried - */ -bool memory_region_is_skip_dump(MemoryRegion *mr); - -/** - * memory_region_set_skip_dump: Set skip_dump flag, dump will ignore this memory - * region + * Returns %true is a memory region is a device backed ram region * * @mr: the memory region being queried */ -void memory_region_set_skip_dump(MemoryRegion *mr); +bool memory_region_is_ram_device(MemoryRegion *mr); /** * memory_region_is_romd: check whether a memory region is in ROMD mode -- cgit 1.4.1 From 4a2e242bbb306ef5c16ce9e7bb2da3bd8a4eb098 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Mon, 31 Oct 2016 09:53:03 -0600 Subject: memory: Don't use memcpy for ram_device regions With a vfio assigned device we lay down a base MemoryRegion registered as an IO region, giving us read & write accessors. If the region supports mmap, we lay down a higher priority sub-region MemoryRegion on top of the base layer initialized as a RAM device pointer to the mmap. Finally, if we have any quirks for the device (ie. address ranges that need additional virtualization support), we put another IO sub-region on top of the mmap MemoryRegion. When this is flattened, we now potentially have sub-page mmap MemoryRegions exposed which cannot be directly mapped through KVM. This is as expected, but a subtle detail of this is that we end up with two different access mechanisms through QEMU. If we disable the mmap MemoryRegion, we make use of the IO MemoryRegion and service accesses using pread and pwrite to the vfio device file descriptor. If the mmap MemoryRegion is enabled and results in one of these sub-page gaps, QEMU handles the access as RAM, using memcpy to the mmap. Using either pread/pwrite or the mmap directly should be correct, but using memcpy causes us problems. I expect that not only does memcpy not necessarily honor the original width and alignment in performing a copy, but it potentially also uses processor instructions not intended for MMIO spaces. It turns out that this has been a problem for Realtek NIC assignment, which has such a quirk that creates a sub-page mmap MemoryRegion access. To resolve this, we disable memory_access_is_direct() for ram_device regions since QEMU assumes that it can use memcpy for those regions. Instead we access through MemoryRegionOps, which replaces the memcpy with simple de-references of standard sizes to the host memory. With this patch we attempt to provide unrestricted access to the RAM device, allowing byte through qword access as well as unaligned access. The assumption here is that accesses initiated by the VM are driven by a device specific driver, which knows the device capabilities. If unaligned accesses are not supported by the device, we don't want them to work in a VM by performing multiple aligned accesses to compose the unaligned access. A down-side of this philosophy is that the xp command from the monitor attempts to use the largest available access weidth, unaware of the underlying device. Using memcpy had this same restriction, but at least now an operator can dump individual registers, even if blocks of device memory may result in access widths beyond the capabilities of a given device (RTL NICs only support up to dword). Reported-by: Thorsten Kohfeldt Signed-off-by: Alex Williamson Acked-by: Paolo Bonzini --- include/exec/memory.h | 6 +++-- memory.c | 67 +++++++++++++++++++++++++++++++++++++++++++++++++++ trace-events | 2 ++ 3 files changed, 73 insertions(+), 2 deletions(-) (limited to 'include/exec') diff --git a/include/exec/memory.h b/include/exec/memory.h index a75b8c3465..9728a2fb1a 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -1480,9 +1480,11 @@ void *qemu_map_ram_ptr(RAMBlock *ram_block, ram_addr_t addr); static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write) { if (is_write) { - return memory_region_is_ram(mr) && !mr->readonly; + return memory_region_is_ram(mr) && + !mr->readonly && !memory_region_is_ram_device(mr); } else { - return memory_region_is_ram(mr) || memory_region_is_romd(mr); + return (memory_region_is_ram(mr) && !memory_region_is_ram_device(mr)) || + memory_region_is_romd(mr); } } diff --git a/memory.c b/memory.c index 7ffcff1d34..33110e9698 100644 --- a/memory.c +++ b/memory.c @@ -1128,6 +1128,71 @@ const MemoryRegionOps unassigned_mem_ops = { .endianness = DEVICE_NATIVE_ENDIAN, }; +static uint64_t memory_region_ram_device_read(void *opaque, + hwaddr addr, unsigned size) +{ + MemoryRegion *mr = opaque; + uint64_t data = (uint64_t)~0; + + switch (size) { + case 1: + data = *(uint8_t *)(mr->ram_block->host + addr); + break; + case 2: + data = *(uint16_t *)(mr->ram_block->host + addr); + break; + case 4: + data = *(uint32_t *)(mr->ram_block->host + addr); + break; + case 8: + data = *(uint64_t *)(mr->ram_block->host + addr); + break; + } + + trace_memory_region_ram_device_read(get_cpu_index(), mr, addr, data, size); + + return data; +} + +static void memory_region_ram_device_write(void *opaque, hwaddr addr, + uint64_t data, unsigned size) +{ + MemoryRegion *mr = opaque; + + trace_memory_region_ram_device_write(get_cpu_index(), mr, addr, data, size); + + switch (size) { + case 1: + *(uint8_t *)(mr->ram_block->host + addr) = (uint8_t)data; + break; + case 2: + *(uint16_t *)(mr->ram_block->host + addr) = (uint16_t)data; + break; + case 4: + *(uint32_t *)(mr->ram_block->host + addr) = (uint32_t)data; + break; + case 8: + *(uint64_t *)(mr->ram_block->host + addr) = data; + break; + } +} + +static const MemoryRegionOps ram_device_mem_ops = { + .read = memory_region_ram_device_read, + .write = memory_region_ram_device_write, + .endianness = DEVICE_NATIVE_ENDIAN, + .valid = { + .min_access_size = 1, + .max_access_size = 8, + .unaligned = true, + }, + .impl = { + .min_access_size = 1, + .max_access_size = 8, + .unaligned = true, + }, +}; + bool memory_region_access_valid(MemoryRegion *mr, hwaddr addr, unsigned size, @@ -1363,6 +1428,8 @@ void memory_region_init_ram_device_ptr(MemoryRegion *mr, { memory_region_init_ram_ptr(mr, owner, name, size, ptr); mr->ram_device = true; + mr->ops = &ram_device_mem_ops; + mr->opaque = mr; } void memory_region_init_alias(MemoryRegion *mr, diff --git a/trace-events b/trace-events index 8ecded5150..f74e1d3d22 100644 --- a/trace-events +++ b/trace-events @@ -121,6 +121,8 @@ memory_region_subpage_read(int cpu_index, void *mr, uint64_t offset, uint64_t va memory_region_subpage_write(int cpu_index, void *mr, uint64_t offset, uint64_t value, unsigned size) "cpu %d mr %p offset %#"PRIx64" value %#"PRIx64" size %u" memory_region_tb_read(int cpu_index, uint64_t addr, uint64_t value, unsigned size) "cpu %d addr %#"PRIx64" value %#"PRIx64" size %u" memory_region_tb_write(int cpu_index, uint64_t addr, uint64_t value, unsigned size) "cpu %d addr %#"PRIx64" value %#"PRIx64" size %u" +memory_region_ram_device_read(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr %#"PRIx64" value %#"PRIx64" size %u" +memory_region_ram_device_write(int cpu_index, void *mr, uint64_t addr, uint64_t value, unsigned size) "cpu %d mr %p addr %#"PRIx64" value %#"PRIx64" size %u" ### Guest events, keep at bottom -- cgit 1.4.1