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target/i386/mshv: Use preallocated page for hvcall

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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>
This commit is contained in:
Magnus Kulke
2025-10-02 09:50:12 +02:00
committed by Paolo Bonzini
parent e7b08dfb90
commit e4a20afce5
3 changed files with 34 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

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);
}