Re: [Qemu-devel] [seabios PATCH 1/2] seabios: build RSDT from XSDT

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Jul 26, 2017 at 11:42:34AM +0200, Paolo Bonzini wrote:
> Old operating systems would like to have a rev1 (ACPI 1.0) FADT, but
> new operating systems would like to have rev3 (ACPI 2.0).
> 
> Since old operating systems do not know about XSDTs, the
> solution is to point the RSDT to a rev1 FADT and the XSDT to a
> rev3 FADT.
> 
> But, edk2 is not able to handle QEMU providing two FADTs and barfs when
> it sees the second; edk2 subscribes to the view that the platform code
> (meaning not only OVMF, but transitively QEMU's ACPI table builder)
> should not handle such hacks; it's common edk2 code that should handle
> FADT rev1 vs. rev3 and RSDT vs. XSDT.

What exactly does it do wrt RSDT?


> These patches make SeaBIOS follow the same model as edk2, the only
> difference being how the two identify ACPI tables from the BIOS
> linker/loader script.  For SeaBIOS, this task is actually much
> simpler since it can just look into the RSDP: if QEMU only
> provides an XSDT, SeaBIOS takes care of building the RSDT and
> rev1 FADT to satisfy ACPI 1.0-compliant operating systems.
> 
> This part makes SeaBIOS build an RSDT out of an existing XSDT,
> patching the RSDP to point to the RSDT.
> 
> Reviewed-by: Phil Dennis-Jordan <phil@philjordan.eu>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  src/fw/paravirt.c | 49 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  src/std/acpi.h    | 11 +++++++++++
>  2 files changed, 59 insertions(+), 1 deletion(-)
> 
> diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
> index 5b23d78..927fd75 100644
> --- a/src/fw/paravirt.c
> +++ b/src/fw/paravirt.c
> @@ -25,6 +25,7 @@
>  #include "x86.h" // cpuid
>  #include "xen.h" // xen_biostable_setup
>  #include "stacks.h" // yield
> +#include "std/acpi.h"
>  
>  // Amount of continuous ram under 4Gig
>  u32 RamSize;
> @@ -147,6 +148,50 @@ static void msr_feature_control_setup(void)
>          wrmsr_smp(MSR_IA32_FEATURE_CONTROL, feature_control_bits);
>  }
>  
> +static void
> +build_compatibility_rsdt(void)
> +{
> +    if (RsdpAddr->rsdt_physical_address)
> +        return;
> +
> +    u64 xsdt_addr = RsdpAddr->xsdt_physical_address;
> +    if (xsdt_addr & ~0xffffffffULL)
> +        return;
> +
> +    struct xsdt_descriptor_rev1 *xsdt = (void*)(u32)xsdt_addr;
> +    void *end = (void*)xsdt + xsdt->length;
> +    struct rsdt_descriptor_rev1 *rsdt;
> +    int rsdt_size = offsetof(struct rsdt_descriptor_rev1, table_offset_entry[0]);
> +    int i;
> +    for (i=0; (void*)&xsdt->table_offset_entry[i] < end; i++) {
> +        u64 tbl_addr = xsdt->table_offset_entry[i];
> +        if (!tbl_addr || (tbl_addr & ~0xffffffffULL))
> +            continue;
> +        rsdt_size += 4;
> +    }
> +
> +    rsdt = malloc_high(rsdt_size);
> +    RsdpAddr->rsdt_physical_address = (u32)rsdt;
> +    RsdpAddr->checksum -= checksum(RsdpAddr,
> +				   offsetof(struct rsdp_descriptor, length));
> +    RsdpAddr->extended_checksum -= checksum(RsdpAddr,
> +					    sizeof(struct rsdp_descriptor));
> +
> +    memcpy(rsdt, xsdt, sizeof(struct acpi_table_header));
> +    rsdt->signature = RSDT_SIGNATURE;
> +    rsdt->length = rsdt_size;
> +    rsdt->revision = 1;
> +    int j;
> +    for (i=j=0; (void*)&xsdt->table_offset_entry[i] < end; i++) {
> +        u64 tbl_addr = xsdt->table_offset_entry[i];
> +        if (!tbl_addr || (tbl_addr & ~0xffffffffULL))
> +            continue;
> +        rsdt->table_offset_entry[j++] = (u32)tbl_addr;
> +    }
> +
> +    rsdt->checksum -= checksum(rsdt, rsdt_size);
> +}
> +
>  void
>  qemu_platform_setup(void)
>  {
> @@ -186,8 +231,10 @@ qemu_platform_setup(void)
>  
>          RsdpAddr = find_acpi_rsdp();
>  
> -        if (RsdpAddr)
> +        if (RsdpAddr) {
> +            build_compatibility_rsdt();
>              return;
> +        }
>  
>          /* If present, loader should have installed an RSDP.
>           * Not installed? We might still be able to continue
> diff --git a/src/std/acpi.h b/src/std/acpi.h
> index c2ea707..a77b53c 100644
> --- a/src/std/acpi.h
> +++ b/src/std/acpi.h
> @@ -133,6 +133,17 @@ struct rsdt_descriptor_rev1
>  } PACKED;
>  
>  /*
> + * ACPI 2.0 Extended System Description Table (XSDT)
> + */
> +#define XSDT_SIGNATURE 0x54445358 // XSDT
> +struct xsdt_descriptor_rev1
> +{
> +    ACPI_TABLE_HEADER_DEF       /* ACPI common table header */
> +    u64 table_offset_entry[0];  /* Array of pointers to other */
> +    /* ACPI tables */
> +} PACKED;
> +
> +/*
>   * ACPI 1.0 Firmware ACPI Control Structure (FACS)
>   */
>  #define FACS_SIGNATURE 0x53434146 // FACS
> -- 
> 2.13.3
>