Re: [Qemu-devel] [PATCH hack dontapply v2 6/7] acpi: aml generation for _CST

[Michael S. Tsirkin]

On Wed, Jul 25, 2018 at 02:42:05PM +0200, Igor Mammedov wrote:
> On Tue, 10 Jul 2018 03:01:33 +0300
> "Michael S. Tsirkin" <address@hidden> wrote:
> 
> > This adds a method called CCST under CPUS.
> > Each CPU will add _CST calling in turn CCST from there.
> > 
> > As _CST needs to change across migration, we use
> > dynamic loading of tables as follows:
> > 
> > - a special scratch buffer, 4K in size is requested from bios
> >   through the loader.
> > - each time CCST executes, buffer address is passed to QEMU
> >   which will write an SSDT table with the _CST package into the buffer.
> > - table is then loaded and a package named \\_SB.CPUS.CSTL is loaded from 
> > there.
> > - table is unloaded, package is then returned to caller
> > 
> > In this way, QEMU can change the package across migration.
> > It will then notify the OSPM which will re-evaluate
> > _CST.
> > 
> > In this proof of concept patch, package generation itself is
> > still a stub, and change notifications are missing.
> > 
> > Signed-off-by: Michael S. Tsirkin <address@hidden>
> > ---
> >  include/hw/acpi/cst.h |   8 ++
> >  hw/acpi/cst.c         | 173 ++++++++++++++++++++++++++++++++++++++++++
> >  hw/acpi/Makefile.objs |   2 +-
> >  3 files changed, 182 insertions(+), 1 deletion(-)
> >  create mode 100644 include/hw/acpi/cst.h
> >  create mode 100644 hw/acpi/cst.c
> > 
> > diff --git a/include/hw/acpi/cst.h b/include/hw/acpi/cst.h
> > new file mode 100644
> > index 0000000000..2e40e87881
> > --- /dev/null
> > +++ b/include/hw/acpi/cst.h
> > @@ -0,0 +1,8 @@
> > +#ifndef HW_ACPI_CST_H
> > +#define HW_ACPI_CST_H
> > +
> > +#include "hw/acpi/bios-linker-loader.h"
> > +
> > +void cst_build_acpi(GArray *table_data, BIOSLinker *linker, uint16_t 
> > ioport);
> > +void cst_register(FWCfgState *s, uint16_t ioport);
> > +#endif
> > diff --git a/hw/acpi/cst.c b/hw/acpi/cst.c
> > new file mode 100644
> > index 0000000000..20dd80aef8
> > --- /dev/null
> > +++ b/hw/acpi/cst.c
> > @@ -0,0 +1,173 @@
> > +#include "qemu/osdep.h"
> > +#include "exec/address-spaces.h"
> > +#include "hw/acpi/aml-build.h"
> > +#include "hw/acpi/cst.h"
> > +#include "hw/acpi/acpi.h"
> > +#include "hw/nvram/fw_cfg.h"
> > +
> > +#define ACPI_SCRATCH_BUFFER_NAME "etc/scratch"
> > +
> > +/* Hack! Incomplete! */
> > +static Aml *build_cst_package(void)
> > +{
> > +    int i;
> > +    Aml *crs;
> > +    Aml *pkg;
> > +    int cs_num = 3;
> > +
> > +    pkg = aml_package(cs_num + 1); /* # of ACPI Cx states + state count */
> > +    aml_append(pkg, aml_int(cs_num)); /* # of ACPI Cx states */
> > +
> > +    for (i = 0; i < cs_num; i++) {
> > +        Aml *cstate = aml_package(4);
> > +
> > +        crs = aml_resource_template();
> > +        aml_append(crs, aml_register(AML_AS_SYSTEM_IO,
> > +            0x8,
> > +            0x0,
> > +            0x100,
> > +            0x1));
> > +        aml_append(cstate, crs);
> > +        aml_append(cstate, aml_int(i + 1)); /* Cx ACPI state */
> > +        aml_append(cstate, aml_int((i + 1) * 10)); /* Latency */
> > +        aml_append(cstate, aml_int(cs_num - i - 1));/* Power */
> > +        aml_append(pkg, cstate);
> > +    }
> > +
> > +    return pkg;
> > +}
> > +
> > +static GArray *cst_scratch;
> > +
> > +/*
> > + * Add an SSDT with a dynamic method named CCST. The method uses the 
> > specified
> > + * ioport to load a table from QEMU, then returns an object named CSTL from
> > + * it.
> > + * Everything is scoped under \\_SB.CPUS.CSTP.
> > + */
> > +void cst_build_acpi(GArray *table_data, BIOSLinker *linker, uint16_t 
> > ioport)
> > +{
> > +    Aml *ssdt, *scope, *field, *method;
> > +    uint32_t cstp_offset;
> > +
> > +    /* Put this in a separate SSDT table */
> > +    ssdt = init_aml_allocator();
> > +
> > +    /* Reserve space for header */
> > +    acpi_data_push(ssdt->buf, sizeof(AcpiTableHeader));
> > +
> > +    cstp_offset = table_data->len +
> > +        build_append_named_dword(ssdt->buf, "\\_SB.CPUS.CSTP");
> > +    scope = aml_scope("\\_SB.CPUS");
> > +    {
> > +        /* buffer in reserved memory to load the table from */
> > +        aml_append(scope, aml_operation_region("CSTB", AML_SYSTEM_MEMORY,
> > +                                               aml_name("\\_SB.CPUS.CSTP"),
> > +                                               4096));
> > +        /* write address here to update the table in memory */
> > +        aml_append(scope, aml_operation_region("CSTR", AML_SYSTEM_IO,
> > +                                               aml_int(ioport),
> > +                                               4));
> > +        field = aml_field("CSTR", AML_DWORD_ACC, AML_LOCK,
> > +                          AML_WRITE_AS_ZEROS);
> > +        {
> > +            aml_append(field, aml_named_field("CSTU", 32));
> > +        }
> > +        aml_append(scope, field);
> > +        method = aml_method("CCST", 0, AML_SERIALIZED);
> > +        {
> > +            Aml *ddbhandle = aml_local(0);
> > +            Aml *cst = aml_local(1);
> > +            /* Write buffer address to update table in memory. */
> > +            aml_append(method, aml_store(aml_name("CSTP"), 
> > aml_name("CSTU")));
> > +            aml_append(method, aml_load("CSTB", ddbhandle));
> > +            aml_append(method, aml_store(aml_name("CSTL"), cst));
> > +            aml_append(method, aml_unload(ddbhandle));
> > +            aml_append(method, aml_return(cst));
> > +        }
> > +        aml_append(scope, method);
> > +    }
> > +    aml_append(ssdt, scope);
> > +    g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
> > +
> > +    /* Why page boundary? no special reason right now but seems like
> > +     * a good idea for future extensions.      
> > +    */
> > +    bios_linker_loader_alloc(linker, ACPI_SCRATCH_BUFFER_NAME, cst_scratch,
> > +                             4096, false /* page boundary, high memory */);
> > +    /* Patch address of allocated memory into the AML so OSPM can retrieve
> > +     * and read it.
> > +     */
> > +    bios_linker_loader_add_pointer(linker,
> > +        ACPI_BUILD_TABLE_FILE, cstp_offset, sizeof(uint32_t),
> > +        ACPI_SCRATCH_BUFFER_NAME, 0);
> > +
> > +    //table_data->data[cstp_offset] = 0x8; /* hack */
> > +
> > +    build_header(linker, table_data,
> > +        (void *)(table_data->data + table_data->len - ssdt->buf->len),
> > +        "SSDT", ssdt->buf->len, 1, NULL, "CSTSSDT");
> > +
> > +    free_aml_allocator();
> > +}
> > +
> > +static GArray *cst_ssdt;
> > +
> > +static void cst_ssdt_setup(void)
> > +{
> > +    AcpiTableHeader *dyn_ssdt_hdr;
> > +    Aml *dyn_ssdt = init_aml_allocator();
> > +
> > +    /* Reserve space for header */
> > +    acpi_data_push(dyn_ssdt->buf, sizeof(AcpiTableHeader));
> > +    aml_append(dyn_ssdt, aml_name_decl("\\_SB.CPUS.CSTL", 
> > build_cst_package()));
> > +
> > +    dyn_ssdt_hdr = (AcpiTableHeader *)dyn_ssdt->buf->data;
> > +
> > +    acpi_init_header(dyn_ssdt_hdr, "SSDT", dyn_ssdt->buf->len, 1, NULL, 
> > "DYNSSDT");
> > +
> > +    dyn_ssdt_hdr->checksum = acpi_checksum((uint8_t *)dyn_ssdt_hdr,
> > +                                           dyn_ssdt->buf->len);
> > +
> > +    /* dyn_ssdt->buf will be freed. copy to cst_ssdt */
> > +    cst_ssdt = g_array_new(false, true, 1);
> > +    g_array_append_vals(cst_ssdt, dyn_ssdt->buf->data, dyn_ssdt->buf->len);
> > +
> > +    free_aml_allocator();
> > +}
> > +
> > +/* Update CST in system memory */
> > +static void cst_ioport_write(void *opaque, hwaddr addr, uint64_t data, 
> > unsigned size)
> > +{
> > +    assert(cst_ssdt);
> > +
> > +    cpu_physical_memory_write(data, cst_ssdt->data, cst_ssdt->len);
> > +}
> > +
> > +static const MemoryRegionOps cst_ops = {
> > +    .write = cst_ioport_write,
> > +    .impl = {
> > +        .min_access_size = 4,
> > +        .max_access_size = 4,
> > +    },
> > +    .endianness = DEVICE_LITTLE_ENDIAN,
> > +};
> > +
> > +static MemoryRegion cst_mr;
> > +
> > +void cst_register(FWCfgState *s, uint16_t ioport)
> > +{
> > +    cst_ssdt_setup();
> > +
> > +    /* Allocate guest scratch memory for the table */
> > +    cst_scratch = g_array_new(false, true, 1);
> > +    acpi_data_push(cst_scratch, 4096);
> > +    fw_cfg_add_file(s, ACPI_SCRATCH_BUFFER_NAME, cst_scratch->data,
> > +                    cst_scratch->len);
> > +
> > +    /* setup io to trigger updates */
> > +    memory_region_init_io(&cst_mr, NULL, &cst_ops, NULL, 
> > "cst-update-request", 4);
> > +    memory_region_add_subregion(get_system_io(), ioport, &cst_mr);
> it eats yet another IO port and a 4K page just for CST.

4K is a scratch pad we can reuse for any dynamic table.

Address is in fact 4K aligned - what if we reuse low bits in the io port
for signal type?  This way we won't burn more ports for the next dynamic
table.

> I'd prefer to extend docs/specs/acpi_cpu_hotplug.txt protocol
> to support passing _CST values via existing registers instead.

That's back to generating AML on the fly all over again.
There's a good reason we moved ACPI to QEMU.
I did code most of it up, and it's an unreadable mess.
Besides, next time we want to add another dynamic table
(like NUMA affinity) we'll have to re-do it again.

> 
> > +}
> > +
> > +/* TODO: API to notify guest of changes */
> > diff --git a/hw/acpi/Makefile.objs b/hw/acpi/Makefile.objs
> > index 11c35bcb44..0119367455 100644
> > --- a/hw/acpi/Makefile.objs
> > +++ b/hw/acpi/Makefile.objs
> > @@ -1,5 +1,5 @@
> >  ifeq ($(CONFIG_ACPI),y)
> > -common-obj-$(CONFIG_ACPI_X86) += core.o piix4.o pcihp.o
> > +common-obj-$(CONFIG_ACPI_X86) += core.o piix4.o pcihp.o cst.o
> >  common-obj-$(CONFIG_ACPI_X86_ICH) += ich9.o tco.o
> >  common-obj-$(CONFIG_ACPI_CPU_HOTPLUG) += cpu_hotplug.o
> >  common-obj-$(CONFIG_ACPI_MEMORY_HOTPLUG) += memory_hotplug.o