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target/i386/mshv: Use preallocated page for hvcall 

There are hvcalls that are invoked during MMIO exits, the payload is of
dynamic size. To avoid heap allocations we can use preallocated pages as
in/out buffer for those calls. A page is reserved per vCPU and used for
set/get register hv calls.

Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
Link: https://lore.kernel.org/r/20250916164847.77883-26-magnuskulke@linux.microsoft.com
[Use standard MAX_CONST macro; mshv.h/mshv_int.h split. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
pull/305/head
Magnus Kulke 10 months ago
committed by Paolo Bonzini
parent
e7b08dfb90
commit
e4a20afce5
3 changed files with 34 additions and 13 deletions
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  1. 2
      accel/mshv/mshv-all.c
  2. 7
      include/system/mshv_int.h
  3. 38
      target/i386/mshv/mshv-cpu.c

2
accel/mshv/mshv-all.c
View File

@ -399,8 +399,8 @@ static int mshv_init_vcpu(CPUState *cpu)
uint8_t vp_index = cpu->cpu_index;
int ret;
mshv_arch_init_vcpu(cpu);
cpu->accel = g_new0(AccelCPUState, 1);
mshv_arch_init_vcpu(cpu);
ret = mshv_create_vcpu(vm_fd, vp_index, &cpu->accel->cpufd);
if (ret < 0) {

7
include/system/mshv_int.h
View File

@ -20,9 +20,16 @@
typedef struct hyperv_message hv_message;
typedef struct MshvHvCallArgs {
void *base;
void *input_page;
void *output_page;
} MshvHvCallArgs;
struct AccelCPUState {
int cpufd;
bool dirty;
MshvHvCallArgs hvcall_args;
};
typedef struct MshvMemoryListener {

38
target/i386/mshv/mshv-cpu.c
View File

@ -34,6 +34,10 @@
#include <sys/ioctl.h>
#define MAX_REGISTER_COUNT (MAX_CONST(ARRAY_SIZE(STANDARD_REGISTER_NAMES), \
MAX_CONST(ARRAY_SIZE(SPECIAL_REGISTER_NAMES), \
ARRAY_SIZE(FPU_REGISTER_NAMES))))
static enum hv_register_name STANDARD_REGISTER_NAMES[18] = {
HV_X64_REGISTER_RAX,
HV_X64_REGISTER_RBX,
@ -151,7 +155,7 @@ int mshv_set_generic_regs(const CPUState *cpu, const hv_register_assoc *assocs,
int cpu_fd = mshv_vcpufd(cpu);
int vp_index = cpu->cpu_index;
size_t in_sz, assocs_sz;
hv_input_set_vp_registers *in;
hv_input_set_vp_registers *in = cpu->accel->hvcall_args.input_page;
struct mshv_root_hvcall args = {0};
int ret;
@ -160,7 +164,7 @@ int mshv_set_generic_regs(const CPUState *cpu, const hv_register_assoc *assocs,
in_sz = sizeof(hv_input_set_vp_registers) + assocs_sz;
/* fill the input struct */
in = g_malloc0(in_sz);
memset(in, 0, sizeof(hv_input_set_vp_registers));
in->vp_index = vp_index;
memcpy(in->elements, assocs, assocs_sz);
@ -172,7 +176,6 @@ int mshv_set_generic_regs(const CPUState *cpu, const hv_register_assoc *assocs,
/* perform the call */
ret = mshv_hvcall(cpu_fd, &args);
g_free(in);
if (ret < 0) {
error_report("Failed to set registers");
return -1;
@ -193,8 +196,8 @@ static int get_generic_regs(CPUState *cpu, hv_register_assoc *assocs,
{
int cpu_fd = mshv_vcpufd(cpu);
int vp_index = cpu->cpu_index;
hv_input_get_vp_registers *in;
hv_register_value *values;
hv_input_get_vp_registers *in = cpu->accel->hvcall_args.input_page;
hv_register_value *values = cpu->accel->hvcall_args.output_page;
size_t in_sz, names_sz, values_sz;
int i, ret;
struct mshv_root_hvcall args = {0};
@ -204,15 +207,14 @@ static int get_generic_regs(CPUState *cpu, hv_register_assoc *assocs,
in_sz = sizeof(hv_input_get_vp_registers) + names_sz;
/* fill the input struct */
in = g_malloc0(in_sz);
memset(in, 0, sizeof(hv_input_get_vp_registers));
in->vp_index = vp_index;
for (i = 0; i < n_regs; i++) {
in->names[i] = assocs[i].name;
}
/* allocate value output buffer */
/* determine size of value output buffer */
values_sz = n_regs * sizeof(union hv_register_value);
values = g_malloc0(values_sz);
/* create the hvcall envelope */
args.code = HVCALL_GET_VP_REGISTERS;
@ -224,16 +226,13 @@ static int get_generic_regs(CPUState *cpu, hv_register_assoc *assocs,
/* perform the call */
ret = mshv_hvcall(cpu_fd, &args);
g_free(in);
if (ret < 0) {
g_free(values);
error_report("Failed to retrieve registers");
return -1;
}
/* assert we got all registers */
if (args.reps != n_regs) {
g_free(values);
error_report("Failed to retrieve registers: expected %zu elements"
", got %u", n_regs, args.reps);
return -1;
@ -243,7 +242,6 @@ static int get_generic_regs(CPUState *cpu, hv_register_assoc *assocs,
for (i = 0; i < n_regs; i++) {
assocs[i].value = values[i];
}
g_free(values);
return 0;
}
@ -1696,6 +1694,19 @@ void mshv_arch_init_vcpu(CPUState *cpu)
{
X86CPU *x86_cpu = X86_CPU(cpu);
CPUX86State *env = &x86_cpu->env;
AccelCPUState *state = cpu->accel;
size_t page = HV_HYP_PAGE_SIZE;
void *mem = qemu_memalign(page, 2 * page);
/* sanity check, to make sure we don't overflow the page */
QEMU_BUILD_BUG_ON((MAX_REGISTER_COUNT
* sizeof(hv_register_assoc)
+ sizeof(hv_input_get_vp_registers)
> HV_HYP_PAGE_SIZE));
state->hvcall_args.base = mem;
state->hvcall_args.input_page = mem;
state->hvcall_args.output_page = (uint8_t *)mem + page;
env->emu_mmio_buf = g_new(char, 4096);
}
@ -1704,7 +1715,10 @@ void mshv_arch_destroy_vcpu(CPUState *cpu)
{
X86CPU *x86_cpu = X86_CPU(cpu);
CPUX86State *env = &x86_cpu->env;
AccelCPUState *state = cpu->accel;
g_free(state->hvcall_args.base);
state->hvcall_args = (MshvHvCallArgs){0};
g_clear_pointer(&env->emu_mmio_buf, g_free);
}

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