On Tue, May 20, 2025 at 01:30:02PM +0200, Magnus Kulke wrote:
> Handle region_add events by invoking the MSHV memory registration
> ioctl to map guest memory into the hypervisor partition. This allows
> the guest to access memory through MSHV-managed mappings.
>
> Note that this assumes the hypervisor will accept regions that overlap
> in userspace_addr. Currently that's not the case, it will be addressed
> in a later commit in the series.
>
> Signed-off-by: Magnus Kulke <magnusku...@linux.microsoft.com>
> ---
> accel/mshv/mem.c | 116 ++++++++++++++++++++++++++++++++++++++--
> accel/mshv/trace-events | 1 +
> include/system/mshv.h | 11 ++++
> 3 files changed, 125 insertions(+), 3 deletions(-)
>
> diff --git a/accel/mshv/mem.c b/accel/mshv/mem.c
> index eddd83ae83..2bbeae4f4a 100644
> --- a/accel/mshv/mem.c
> +++ b/accel/mshv/mem.c
> @@ -13,13 +13,123 @@
>
> #include "qemu/osdep.h"
> #include "qemu/error-report.h"
> +#include "hw/hyperv/linux-mshv.h"
> #include "system/address-spaces.h"
> #include "system/mshv.h"
> +#include "exec/memattrs.h"
> +#include <sys/ioctl.h>
> +#include "trace.h"
> +
> +static int set_guest_memory(int vm_fd, const mshv_user_mem_region *region)
> +{
> + int ret;
> +
> + ret = ioctl(vm_fd, MSHV_SET_GUEST_MEMORY, region);
> + if (ret < 0) {
> + error_report("failed to set guest memory");
> + return -errno;
> + }
> +
> + return 0;
> +}
> +
> +static int map_or_unmap(int vm_fd, const MshvMemoryRegion *mr, bool add)
Change "add" to "map" to match the name of the function.
> +{
> + struct mshv_user_mem_region region = {0};
> +
> + region.guest_pfn = mr->guest_phys_addr >> MSHV_PAGE_SHIFT;
> + region.size = mr->memory_size;
> + region.userspace_addr = mr->userspace_addr;
> +
> + if (!add) {
> + region.flags |= (1 << MSHV_SET_MEM_BIT_UNMAP);
Use BIT() like you did in other places?
> + return set_guest_memory(vm_fd, ®ion);
> + }
> +
> + region.flags = (1 << MSHV_SET_MEM_BIT_EXECUTABLE);
Should this be always set? Is there a way to get more information from
the caller or QEMU's core memory region management logic?
> + if (!mr->readonly) {
> + region.flags |= (1 << MSHV_SET_MEM_BIT_WRITABLE);
> + }
> +
> + return set_guest_memory(vm_fd, ®ion);
> +}
> +
> +static int set_memory(const MshvMemoryRegion *mshv_mr, bool add)
> +{
> + int ret = 0;
> +
> + if (!mshv_mr) {
> + error_report("Invalid mshv_mr");
> + return -1;
> + }
> +
> + trace_mshv_set_memory(add, mshv_mr->guest_phys_addr,
> + mshv_mr->memory_size,
> + mshv_mr->userspace_addr, mshv_mr->readonly,
> + ret);
> + return map_or_unmap(mshv_state->vm, mshv_mr, add);
> +}
> +
> +/*
> + * Calculate and align the start address and the size of the section.
> + * Return the size. If the size is 0, the aligned section is empty.
> + */
> +static hwaddr align_section(MemoryRegionSection *section, hwaddr *start)
> +{
> + hwaddr size = int128_get64(section->size);
> + hwaddr delta, aligned;
> +
> + /*
> + * works in page size chunks, but the function may be called
> + * with sub-page size and unaligned start address. Pad the start
> + * address to next and truncate size to previous page boundary.
> + */
> + aligned = ROUND_UP(section->offset_within_address_space,
> + qemu_real_host_page_size());
> + delta = aligned - section->offset_within_address_space;
> + *start = aligned;
> + if (delta > size) {
> + return 0;
> + }
> +
> + return (size - delta) & qemu_real_host_page_mask();
> +}
>
> void mshv_set_phys_mem(MshvMemoryListener *mml, MemoryRegionSection *section,
> bool add)
> {
> - error_report("unimplemented");
> - abort();
> -}
> + int ret = 0;
> + MemoryRegion *area = section->mr;
> + bool writable = !area->readonly && !area->rom_device;
> + hwaddr start_addr, mr_offset, size;
> + void *ram;
> + MshvMemoryRegion tmp, *mshv_mr = &tmp;
> +
> + if (!memory_region_is_ram(area)) {
> + if (writable) {
> + return;
> + }
> + }
> +
I don't follow the check here. Can you put in a comment?
Thanks,
Wei.
> + size = align_section(section, &start_addr);
> + if (!size) {
> + return;
> + }
> +
> + mr_offset = section->offset_within_region + start_addr -
> + section->offset_within_address_space;
>
> + ram = memory_region_get_ram_ptr(area) + mr_offset;
> +
> + memset(mshv_mr, 0, sizeof(*mshv_mr));
> + mshv_mr->guest_phys_addr = start_addr;
> + mshv_mr->memory_size = size;
> + mshv_mr->readonly = !writable;
> + mshv_mr->userspace_addr = (uint64_t)ram;
> +
> + ret = set_memory(mshv_mr, add);
> + if (ret < 0) {
> + error_report("Failed to set memory region");
> + abort();
> + }
> +}
